JP6484318B2 - Ionizer, mass spectrometer and ionization method - Google Patents

Description

  The present invention relates to a charging device for fine particles dispersed in air or gas, and an analysis device for the charged fine particles, for example, a mass analysis device.

  As an ionization method of a mass spectrometer, an electron ionization method (EI method) in which a sample molecule is irradiated with an electron beam and a chemical ionization method (CI method) in which ions are generated by a molecular reaction have been known for a long time. However, these methods have limited the range of substances that can be analyzed, such as difficulty in analyzing hardly volatile substances. On the other hand, the fast atom bombardment method (FAB), in which accelerated neutral atoms collide with a sample and ionized, has been developed, and mass spectrometry can be performed even for refractory substances. All of these methods are ionization methods in a vacuum.

  Recently, electrospray ionization (ESI) and matrix-assisted laser desorption / ionization (MALDI) have been developed. Since these ionization methods are softer than conventional methods, it has become possible to measure proteins having a molecular weight of 10,000 to several hundred thousand required in the biochemical field.

  In addition, since the operability of the sample is easy and ionization efficiency is high, an ionization method (API) at atmospheric pressure rather than in vacuum is desired. There are mainly the following two methods in the atmospheric pressure ionization method (API). Atmospheric pressure chemical ionization (APCI) is used for spraying by electric discharge, and electrospray ionization (ESI) is used for using electric field.

  Electrospray ionization (ESI) is a method in which a sample solution is guided to a capillary with a high voltage of about 3 to 5 kV applied to the tip, and atomized gas is allowed to flow from the outside of the capillary and sprayed. A sample ion having a sign is obtained.

  On the other hand, as a specific example of the atmospheric pressure chemical ionization method (APCI), Patent Document 1 discloses that the primary ions generated by the discharge of the primary ion generating gas are mixed with the sample gas and included in the sample gas by the ion molecule reaction. A method for ionizing a substance is disclosed.

  FIG. 4 shows an apparatus configuration diagram of Patent Document 1. In FIG. The outline of the atmospheric pressure chemical ionization method (APCI) will be described below with reference to FIG.

  The atmospheric pressure ionization mass spectrometer of Patent Document 1 includes an ion generation unit 905 and a mixing unit 910. Inside the ion generation unit 905, a needle electrode 914 to which a high voltage is applied by a power source 913 is installed. The primary ion generating gas 901 is introduced into the ion generating unit 905 from the first gas introduction port 915 and is ionized by corona discharge generated at the tip of the needle electrode 914 to generate primary ions.

  A part of the primary ion generating gas 901 flows into the mixing unit 910 from the opening 916 of the first electrode. The primary ions are introduced into the mixing unit 910 by the gas flow and the potential difference between the needle electrode 914 and the first electrode 909. The remaining portion of the gas 901 (gas 903) is discharged out of the ion source from the gas discharge port 917. The sample gas 902 introduced from the gas inlet 918 is mixed with primary ions in the mixing unit 910 to generate secondary ions. In the mixing unit 910, the primary ion generating gas 901 and the sample gas 902 are sufficiently mixed, so that secondary ions are generated from the sample gas 902 with high efficiency. The generated secondary ions are introduced into the high-vacuum mass analysis section through the pores 919 of the second electrode 912 due to the potential difference between the first electrode 909 and the second electrode 912, and are separated and detected.

JP 06-310091 (published on November 4, 1994)

  As described above, the electrospray ionization method (ESI) and the atmospheric pressure chemical ionization method (APCI) have been described as specific examples of the atmospheric pressure ionization method (API).

  However, electrospray ionization (ESI) involves: 1. the sample contaminates the ion source; 2. It is necessary to increase ionization efficiency in order to perform ionization with high accuracy. There is a problem that a high electric field of kV order is required.

  The atmospheric pressure chemical ionization method (APCI) of Patent Document 1 has the same problems as in the above 1-3. Furthermore, in the method of ionizing a gas or sample by discharge or plasma, the energy of the discharge field is high, and therefore active ions and radicals are generated depending on the type of primary ion generating gas. Such gases cannot be used because they may alter the sample. Moreover, since the gas type is limited, there is a problem that a gas that increases ionization efficiency cannot be used. In addition, two chambers of an ion generation unit 905 and a mixing unit 910 are necessary to ionize the target substance, and the configuration is complicated, and also for gas transportation for passing through two steps of primary ionization and secondary ionization. There is a problem that a complicated configuration is also required.

  The present invention has been made in view of the above problems, and an object of the present invention is to realize an apparatus capable of ionizing a sample very softly under a atmospheric pressure with a simple configuration.

Ionization device according to the present invention, the discharge port of the sample gas and any carrier gas inlet for introducing therein the discharge outlet and unwanted emissions to release the generated ions to the outside so as to be discharged to the outside An ionization part consisting of a chamber having a discharge port provided separately from,
And the electron-emitting device which is provided facing the ionization portion,
A counter electrode provided facing the ionization portion so as to face the electron-emitting device ;
A power source capable of applying a voltage between the electron-emitting device and the counter electrode ;
A voltage lower than the discharge start voltage of the sample gas is applied between the electron-emitting device and the counter electrode, and electrons are emitted from the electron-emitting device into the ionization portion into which the sample gas has been introduced. Thus, the sample gas is configured to be ionized.

The outlet for releasing the previous SL generated ions to the exterior is preferably pores.

  The sample gas preferably contains protein.

  It is preferable that the ionization portion is in an atmospheric pressure to medium vacuum state.

  In the electron-emitting device, a first electrode, an electron acceleration layer, and a second electrode are formed in this order, and a voltage is applied between the first electrode and the second electrode. It is preferable that electrons are emitted from the second electrode to the outside of the device.

  The electron acceleration layer preferably includes at least one of resin, insulating fine particles, and conductive fine particles.

  A mass spectrometer according to the present invention includes the ionization apparatus according to the present invention.

  The present invention has been made in view of the above problems, and can realize an apparatus capable of ionizing a sample very softly under a atmospheric pressure with a simple configuration.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates a first embodiment and is a cross-sectional view illustrating a configuration of an ionization apparatus of the present invention. FIG. 5 is a cross-sectional view showing an electron-emitting device constituting the ionization apparatus of the present invention, showing a second embodiment. It is sectional drawing which shows 3rd Embodiment and shows the electron-emitting element which comprises the ionization apparatus of this invention. It is sectional drawing which shows a prior art and shows the structure of an atmospheric pressure chemical ionization method (APCI) apparatus.

Embodiment 1
The ionization apparatus according to the first embodiment will be described below with reference to the drawings.

  FIG. 1 shows a cross-sectional view of the configuration of the ionization apparatus of the present invention.

  The ionization apparatus 10 according to the first embodiment of the present invention is an apparatus that ionizes a gas introduced into the ionization unit 15, and includes at least an ionization unit 15, an electron emission element 1, a counter electrode 14, and an introduction port for introducing a sample. Have.

  The inlet for introducing the sample is a gas flow path formed through the outer wall of the ionizer 10. The electron-emitting device 1 is provided so as to face the ionization unit 15, and is used by applying a voltage from the power source 7. Further, a counter electrode 14 is provided to face the electron-emitting device 1.

  In the first embodiment, the ionization apparatus 10 having the above configuration is integrated with the mass analysis unit 20 through the pores 19 to form a mass analysis apparatus. Further, a gas discharge port 13 for discharging unnecessary components out of the gas introduced into the ionization unit 15 is also provided.

  Next, details of the electron-emitting device 1 will be described.

  The electron-emitting device 1 includes a first electrode 2 that is also a substrate, a second electrode 3, and an electron acceleration layer 4 that is sandwiched therebetween. In addition, the first electrode 2 and the second electrode 3 are connected to a power source 7 so that a voltage can be applied between the first electrode 2 and the second electrode 3 that are arranged to face each other. The electron-emitting device 1 applies a voltage between the first electrode 2 and the second electrode 3 so that a current flows between the first electrode 2 and the second electrode 3, that is, the electron acceleration layer 4. A part of the second electrode 3 is transmitted as a ballistic electron by a strong electric field generated by an applied voltage, or is transmitted through or emitted from a gap (a fine hole) between the second electrodes 3.

  The first electrode 2 is an electrode substrate that also functions as a substrate, and is composed of a plate-like body formed of a conductor.

  The first electrode 2 functions not only as a support for the electron-emitting device 1 but also as an electrode. Therefore, the first electrode 2 only needs to have a certain degree of strength and appropriate conductivity. For example, a substrate formed of a metal such as stainless steel (SUS), Al, Ti, or Cu, or a semiconductor substrate such as Si, Ge, or GaAs can be used.

  The first electrode 2 may be a structure in which an electrode made of a conductive film is formed on an insulating substrate such as a glass substrate or a plastic substrate.

  For example, when a glass substrate is used, the surface of the glass substrate serving as an interface with the electron acceleration layer 4 may be covered with a conductive film using magnetron sputtering or the like and used as the first electrode 2.

  As a material for the conductive film, it is preferable to use a conductive material with high antioxidation power, and more preferable to use a noble metal if stable operation in the atmosphere is desired. For the conductive film, ITO, which is an oxide conductive material and is widely used for transparent electrodes, is also useful.

  Moreover, when the 1st electrode 2 is comprised with the electroconductive film which coat | covers an insulator board | substrate, since a toughness is requested | required of an electroconductive film, you may laminate | stack a some electroconductive film.

  For example, a Ti film is formed on the surface of a glass substrate with a thickness of 200 nm, a metal laminated film in which a Cu film is formed with a thickness of 1000 nm, or a Mo film is formed on the surface of the glass substrate with a thickness of 30 nm. A metal laminated film in which an Al film is formed with a thickness of 130 nm and a Mo film is formed thereon with a thickness of 50 nm may be used as the first electrode 2, but is not limited to these materials and values. When a glass substrate is covered with a Ti thin film and a Cu thin film, a tough conductive thin film can be formed.

  Note that the electrode may be formed by patterning the conductive film on the surface of the insulator substrate into a square or the like using a known photolithography or mask.

  The second electrode 3 is to be paired with the first electrode 2 to apply a voltage in the electron acceleration layer 4. Therefore, any material that can be applied with voltage can be used without particular limitation. However, from the standpoint that electrons accelerated and become high energy in the electron acceleration layer 4 are transmitted with as little energy loss as possible and emitted, a material having a low work function and capable of forming a thin film is higher. The effect can be expected. Examples of such a material include gold, silver, carbon, tungsten, titanium, aluminum, palladium, and the like whose work function corresponds to 4 to 5 eV. In particular, assuming operation at atmospheric pressure, gold without oxide and sulfide formation reaction is the best material. In addition, silver, palladium, tungsten, and the like, which have a relatively small oxide formation reaction, are materials that can withstand actual use without problems. The film thickness of the second electrode 3 is important as a condition for efficiently emitting electrons from the electron-emitting device 1 to the outside, and the minimum film thickness for causing the second electrode 3 to function as a planar electrode is 10 nm. If the film thickness is less than that, electrical conduction cannot be secured. Furthermore, it is preferable to set it as the range of 10-300 nm.

  The electron acceleration layer 4 only needs to contain conductive fine particles or an insulating material. In the first embodiment, an example in which the electron acceleration layer 4 includes both conductive fine particles and an insulating material will be described. Specifically, the electron acceleration layer 4 includes insulating fine particles 5 and conductive fine particles 6.

  Here, as the metal species of the conductive fine particles 6, any metal species can be used on the operation principle of generating ballistic electrons. However, for the purpose of avoiding oxidative degradation when operated at atmospheric pressure, it is necessary to be a metal with high antioxidation power, and a noble metal is preferable, and examples thereof include materials such as gold, silver, platinum, palladium, and nickel. Such conductive fine particles 6 can be produced by using a known fine particle production technique such as sputtering or spray heating, and commercially available conductive fine particle powders such as silver nanoparticles produced and sold by Applied Nano Laboratory. Is also available.

  Here, the average diameter of the conductive fine particles 6 must be smaller than the size of the insulating fine particles 5 to be described below because it is necessary to control the conductivity, and is more preferably 3 to 10 nm. By setting the average diameter of the conductive fine particles 6 to be smaller than the particle diameter of the insulating fine particles 5, preferably 3 to 10 nm, a conductive path by the conductive fine particles 6 is not formed in the electron acceleration layer 4. Insulation breakdown in the acceleration layer 4 is less likely to occur. By using the conductive fine particles 6 having a particle diameter within the above range, ballistic electrons are efficiently generated.

The insulating fine particles 5 can be used without particular limitation as long as the material has insulating properties. However, the weight percentage of the insulating fine particles 5 in the whole fine particles constituting the electron acceleration layer 4 is 80 to 95%, and the size thereof has a heat radiation effect superior to the conductive fine particles 6. The diameter (average diameter) of the insulating fine particles 5 is preferably 10 to 1000 nm, and more preferably 12 to 110 nm. The material of the insulating fine particles 5 is practically SiO ₂ , Al ₂ O ₃ or TiO ₂ .

  As the electron acceleration layer 4 is thinner, a stronger electric field is applied, so that electrons can be accelerated by applying a low voltage. However, since the resistance can be adjusted in the layer thickness direction, the layer thickness is more preferably 12 to 6000 nm. Is preferably 300 to 6000 nm.

  Next, the principle of electron emission will be described. Most of the electron acceleration layer 4 is composed of insulating fine particles 5, and conductive fine particles 6 are scattered in the gaps. The ratio between the insulating fine particles 5 and the conductive fine particles 6 is such that the weight ratio of the insulating fine particles 5 to the total weight of the insulating fine particles 5 and the conductive fine particles 6 corresponds to 80%. The conductive fine particles 6 adhering to / contacting with each other are about six particles.

  Since the electron acceleration layer 4 is composed of insulating fine particles 5 and a small number of conductive fine particles 6, it has semiconductivity. Therefore, when a voltage is applied to the electron acceleration layer 4, a very weak current flows. The voltage-current characteristic of the electron acceleration layer 4 shows a so-called varistor characteristic, and the current value is rapidly increased as the applied voltage increases. A part of this current becomes ballistic electrons due to a strong electric field in the electron acceleration layer 4 formed by the applied voltage, and is transmitted through the second electrode 3 or passes through the gap and emitted to the outside of the electron-emitting device 1.

  Here, the electron emission mechanism of the electron-emitting device 1 will be described.

  When a voltage is applied between the first electrode 2 and the second electrode 3, the electron-emitting device 1 starts from the first electrode 2 in the electron acceleration layer 4 between the first electrode 2 and the second electrode 3. Electrons move to the surface of the insulating fine particles 5. Since the inside of the insulating fine particles 5 has a high resistance, electrons are conducted through the surface of the insulating fine particles 5.

  At this time, electrons are trapped by impurities on the surface of the insulating fine particles 5, oxygen defects when the insulating fine particles 5 are oxides, or contacts between the insulating fine particles 5. The trapped electrons work as fixed charges.

  As a result, a strong electric field is generated on the surface of the electron acceleration layer 4 by combining the applied voltage and the electric field generated by the trapped electrons, and the electrons are accelerated by the strong electric field, and the electrons are emitted from the second electrode 3. It is thought.

  In the first embodiment, the conductive fine particles 6 are added to the surface of the insulating fine particles 5 by adding the conductive fine particles 6 to the electron accelerating layer 4 to control the electron conduction on the surface of the insulating fine particles 5. It is possible to control the amount of electron emission of the current value flowing through 4.

  An example of a manufacturing method of the electron-emitting device 1 will be described. First, the electron acceleration layer 4 is formed on the first electrode 2 by applying a dispersion solution in which the insulating fine particles 5 and the conductive fine particles 6 are dispersed using a spin coating method. Here, the solvent used in the dispersion solution can be used without particular limitation as long as the insulating fine particles 5 and the conductive fine particles 6 can be dispersed and dried after coating. For example, toluene, benzene, xylene, hexane, Tetradecane or the like can be used. In addition, for the purpose of improving the dispersibility of the conductive fine particles 6, an alcoholate treatment may be performed as a pretreatment. Further, a predetermined film thickness can be obtained by repeating film formation and drying by a spin coating method a plurality of times. The electron acceleration layer 4 can be formed by a method such as a dropping method or a spray coating method in addition to the spin coating method. Then, the second electrode 3 is formed on the electron acceleration layer 4. For example, a magnetron sputtering method may be used to form the second electrode 3.

  Next, an ionization operation will be described.

  A carrier gas 21 is introduced into the gas introduction port 11 and a sample gas 22 is introduced into the gas introduction port 12 as a gas to be ionized by the ionization unit 15.

  The sample gas 22 is a target substance to be ionized, and is a target substance to be subjected to mass analysis in a mass spectrometer. The sample gas 22 is described as gas for convenience, but is not limited to gas gas, and includes the following “state that can be handled as gas”. When the analysis target substance is a volatile organic solvent, it is a gas gas, but when it is a substance other than a gas at normal temperature and pressure, the following method can be used to make it “a state that can be handled as a gas”. For example, in the case of liquid at room temperature and normal pressure, aerosol (aerosol) state, that is, using another gas pressure, a sample (for example, protein) is blown out in the form of a mist, and solid or liquid fine particles are dispersed and suspended in the gas. What is necessary is just to let it be in the state. As another method, a liquid or a solid can be handled as a gas by using heating by a heater or laser irradiation.

The carrier gas 21 is a gas provided simultaneously with the sample gas 22 in order to efficiently ionize the sample gas 22, and a rare gas such as Ar or He or an inert gas such as N ₂ is used. However, when the sample gas 22 can be ionized alone, the carrier gas 21 need not be introduced.

  In the ionization unit 15, the sample gas 22 and the carrier gas 21 are mixed, and this mixed gas is referred to as “analysis gas” in the first embodiment. That is, the “analysis gas” includes both the sample gas 22 to be analyzed and the carrier gas 21 for efficiently ionizing the sample gas 22.

  By adjusting the flow rates of the sample gas 22 and the carrier gas 21, that is, the introduction ratio and the flow rate of the exhaust gas 23, the usage / consumption amount of the sample gas 22, the ionization efficiency of the analysis gas, and the mass analysis unit 20 are introduced. The number of analysis ions to be performed, the ratio of ions derived from the sample gas 22 contained in the analysis ions, the pressure of the analysis gas in the ionization unit 15, and the like can be controlled. In this way, in the first embodiment, the analysis gas in the ionization unit 15 is maintained in an atmospheric pressure state.

  When a voltage of 5 to 20 V is applied to the power supply 7 in this state, electrons are emitted from the electron-emitting device 1 toward the ionization unit 15. At this time, the energy of the electrons is as low as about 15 eV or less. In this state, electrons emitted from the electron-emitting device 1 stay in the vicinity of the surface of the device. Therefore, by applying an extraction voltage of about several hundred volts to the counter electrode 14, the emitted electrons are extracted in the direction of the counter electrode 14. . Since the extracted electrons have low energy, they are trapped by the molecules when colliding with the molecules of the analysis gas, causing an “electron attachment” phenomenon to generate negative ions.

  The ions generated in the ionization unit 15 as described above are transported to the mass analysis unit 20 through the pores 19. Specifically, the mass analysis unit 20 includes a mass separation unit, a detection unit, and the like, and can analyze the mass. As the driving force for this transport, the pressure of the analysis gas, that is, the pressure difference between the ionization unit 15 and the mass analysis unit 20 may be used, or the potential difference between them may be used by providing electrodes at appropriate locations. I do not care.

  So far, the ionization by the ionization apparatus of Embodiment 1 has been described, but the effects obtained by the present invention will be described.

  In Embodiment 1, since the analysis gas in the ionization part 15 was made into atmospheric pressure, many analysis gas molecules exist compared with a vacuum state or a low gas pressure state. For this reason, the ionization efficiency is relatively high, and the effect of efficiently generating ions derived from the analysis gas is achieved. In addition, since electrons can be emitted at atmospheric pressure, gasification of the sample can be performed at atmospheric pressure, and operability is facilitated.

  By performing ionization using the electron attachment phenomenon of the first embodiment, the following effects can be obtained compared to the conventional method.

  The first is that extremely soft ionization by low energy electrons is possible. In the atmospheric pressure chemical ionization method (APCI) in which gas is ionized by discharge or plasma described in Patent Document 1, a high voltage on the order of several kV is required as a voltage for generating corona discharge at the tip of the needle electrode. The energy of the field is high. For this reason, depending on the atmospheric gas species, active ions and radicals are generated, which may alter and degrade the sample material to be analyzed. Furthermore, there is a problem that the degree of freedom in selecting the atmospheric gas is narrow and the gas type is limited, so that a gas that increases ionization efficiency cannot be used. On the other hand, in the first embodiment, since an electron attachment phenomenon due to low energy electrons of several tens eV or less which is lower than the discharge start voltage of the analysis gas is used, unnecessary radicals are not generated, and the sample material to be analyzed is It has the effect of being hard to break.

  Second, it can be realized with a simple configuration. In the atmospheric pressure chemical ionization method (APCI) described in Patent Document 1, primary ions are first generated using a carrier gas, and then mixed with the sample gas to ionize the sample gas. Therefore, it is necessary to divide ionization into two stages, and it is necessary to prepare two rooms for ionization. On the other hand, in the first embodiment, in order to use the electron adhesion phenomenon, both the sample gas and the carrier gas are introduced and mixed, and then ionized by the ionization unit. That is, there is an effect that the structure and the process are simple.

  The third has the following secondary effects when, for example, protein is analyzed. A protein consists of a one-dimensional chain structure part of an amino acid (hereinafter referred to as the main chain) and a modifying molecule that characterizes the protein. When electron attachment is applied to a protein, the main chain of the amino acid is preferentially fragmented and modified. The molecule has the property that it remains attached to the main chain. As a result, the modified molecule remains in the main chain, which is advantageous for determining the modification site of the modified protein, and is very effective for protein analysis.

  Furthermore, by performing electron emission using the electron-emitting device 1 of Embodiment 1, the following effects can be obtained compared to the conventional method.

  The first is the electron emission efficiency. Conventionally, atmospheric pressure photoelectron emission has been almost the only method for emitting electrons into atmospheric pressure. On the other hand, by using the electron-emitting device 1, electrons can be obtained with high efficiency about 100,000 times that of atmospheric pressure photoelectron emission. As a result, there is an effect that electrons can be obtained with extremely high efficiency.

  Second, ion generation conditions are wide. Assume that ionization may be required in a medium vacuum state that can be realized by, for example, a rotary pump, depending on the supply status of the sample gas and carrier gas and the request for the gas ratio. In the atmospheric pressure chemical ionization method (APCI) described in Patent Document 1, since a gas or a sample is ionized by discharge or plasma, the discharge condition or plasma generation condition varies greatly depending on the degree of vacuum of the gas. When the device is designed to ionize at atmospheric pressure, it is necessary to change each condition greatly in order to ionize the above-mentioned medium vacuum state gas. Sometimes. On the other hand, if the electron-emitting device 1 of the first embodiment is used, it is possible to emit electrons under almost the same conditions at both atmospheric pressure and the above-described medium vacuum. Ionization is possible with the same device, and there is an effect that the versatility, applicability, and flexibility of the device are high. The medium vacuum state mentioned above refers to the range from atmospheric pressure to the degree of vacuum that can be reached with a rotary pump. The ultimate vacuum of a general rotary pump is about 0.1 Pa. In the first embodiment, an example in which the analysis gas in the ionization unit 15 is maintained in an atmospheric pressure state is shown. However, if the flow rates of the sample gas 22, the carrier gas 21, and the exhaust gas 23 are adjusted, the pressure of the analysis gas in the ionization unit 15 Can be controlled to a medium vacuum, so that the above-described ionization can be easily performed.

  In the first embodiment, the example in which the electron acceleration layer 4 is made of insulating fine particles and conductive fine particle resin has been shown. However, actually, the structure made of only insulating fine particles, the structure made of resin and conductive fine particles, etc. Various combinations are possible. The optimum ratio of each element, the average diameter of fine particles, and the like may have different conditions depending on the combination. However, the electron acceleration layer performs its function by including at least one of resin, insulating fine particles, and conductive fine particles. .

  In addition, although the form of the mass spectrometer was shown in the first embodiment as described above, this is merely an example of the application, and the technical idea of the present application is as long as the ionizer 10 generates ions. Any form is acceptable. For example, the ionizer 10 may be a single ion generator.

[Embodiment 2]
The ionization apparatus according to the second embodiment will be described below with reference to the drawings.

FIG. 2 shows a cross-sectional view of the electron-emitting device 39 constituting the ionization apparatus according to the second embodiment of the present invention. The ionization apparatus according to the second embodiment of the present invention is different from the first embodiment in that an electron-emitting device 39 is provided instead of the electron-emitting device 1. Other points are common to the first embodiment.
Regarding the numbers of the elements constituting the electron-emitting device 39, the same reference numerals are given to the same elements as those in the electron-emitting device 1 of the first embodiment.

  First, an outline of the electron-emitting device 39 will be described.

  The electron emission element 39 is formed on the first electrode 2, the electron emission control insulating film 32 formed on the first electrode 2 and having a plurality of small holes 32 a penetrating in the film thickness direction, and the electron emission control insulating film 32. An electron acceleration layer 33 having an insulating fine particle 5 embedded on the electron emission control insulating film 32 and in each small hole 32a of the electron emission control insulating film 32; A carbon thin film 34 formed thereon and a second electrode 3 formed on the carbon thin film 34 are provided.

  In addition, the electron-emitting device 39 can emit electrons by including a power source 37 that applies a voltage between the first electrode 2 and the second electrode 3 of the electron-emitting device 39. At this time, the first electrode 2 is electrically connected to the negative pole of the power source 37, and the second electrode 3 is electrically connected to the positive pole of the power source 37.

  By applying a voltage between the first electrode 2 and the second electrode 3, electrons emitted from the first electrode 2 are converted into the electron acceleration layer 33 at the position of the small hole 32 a of the electron emission control insulating film 32. It is configured to be accelerated and discharged from the second electrode 3 to the outside.

  That is, the electron-emitting device 39 according to the second embodiment has the electron emission control insulating film 32 having a plurality of uniformly arranged small holes 32a on the first electrode 2 side between the first and second electrodes. Electrons can be emitted uniformly from the outer surface of the second electrode 3.

  Here, the mechanism of electron emission of the electron-emitting device 39 of Embodiment 2 will be described. Similarly to the first embodiment, when a voltage is applied between the first electrode 2 and the second electrode 3, the electron acceleration layer 33 between the first electrode 2 and the first electrode 2 and the second electrode 3 is applied. Electrons move to the surface of the insulating fine particles 5 inside. Since the inside of the insulating fine particles 5 has a high resistance, electrons are conducted through the surface of the insulating fine particles 5.

  At this time, electrons are trapped by impurities on the surface of the insulating fine particles 5, oxygen defects when the insulating fine particles 5 are oxides, or contacts between the insulating fine particles 5. The trapped electrons work as fixed charges.

  As a result, a strong electric field is generated on the surface of the electron acceleration layer 33 by combining the applied voltage and the electric field generated by the trapped electrons, and the electrons are accelerated by the strong electric field, and the electrons are emitted from the second electrode 3. The

  In the first embodiment, the conductive fine particles 6 are added to the electron acceleration layer 4. However, when the insulating fine particles 5 are used for the electron acceleration layer 33 as shown in the second embodiment, the conductive fine particles 6 are added. It is possible to emit electrons even in a configuration that does not include it.

  On the other hand, when this mechanism is viewed from a macro viewpoint, the electron emission control insulating film 32 is provided with a plurality of small holes 32a penetrating in the thickness direction, and the insulating properties of the electron acceleration layer 33 entering the small holes 32a. Electrons move from the first electrode 2 to the fine particles 5, and electrons are emitted by the mechanism.

  The electron emission control insulating film 32 has a high electric resistance, and electrons from the first electrode 2 do not move from the electron emission control insulating film 32 to the upper layer, so that electron emission does not occur.

  As a result, electrons are emitted only from the small holes 32a, and the electrons are uniformly emitted from the small holes 32a arranged in the entire electron-emitting device 39. Further, since the device structure is such that electron emission occurs according to the pattern of the electron emission control insulating film 32, electrons are emitted with good controllability.

  As described above, since the electron-emitting device 39 according to the second embodiment has a pattern structure in which the electron emission control insulating film 32 emits electrons (small holes 32a) and the non-electron emission parts are alternately arranged. Therefore, electrons can be emitted uniformly and with good controllability.

  The voltage applied to the electron-emitting device 39 may be either a DC voltage or an AC voltage, but an AC voltage with a relatively stable electron emission amount is preferred. Hereinafter, in the present specification, the term “voltage” refers to both “AC voltage” and “DC voltage”.

  Further, in the manufacturing method of the electron-emitting device 39 according to the second embodiment, the step (A) of forming the electron emission control insulating film 32 having a plurality of small holes 32a penetrating in the film thickness direction on the first electrode 2. (B) forming an electron acceleration layer 33 including insulating fine particles 5 on the first electrode 2 so as to cover the electron emission control insulating film 32; and a second electrode on the electron acceleration layer 33. 3 (C). With this manufacturing method, the electron-emitting device 39 can be manufactured.

  The electron-emitting device 39 includes, for example, an inorganic film such as a silicon oxide film, a silicon nitride film, and a silicon oxynitride film, a silicone resin film, an acrylic resin film, a polyimide resin film, and an epoxy resin. An insulating film such as an organic film such as a film, a polyester resin film, a polyurethane resin film, or a polystyrene resin film may be used. Among these embodiments, a silicon oxide film, a silicon nitride film, a silicone resin film, an acrylic resin film, and a polyimide resin film are more preferable from the viewpoints of resistance value, heat resistance, water absorption, mechanical strength, and the like.

  The film thickness of these insulating films varies depending on the magnitude of the voltage applied to the electron-emitting device, but can be set to 0.1 to 3 μm, for example.

  Further, the electron emission control insulating film 32 may be a single layer film or a laminated film of these various insulating films.

  In addition, the size, shape, density, and the like of the plurality of small holes 32a formed in the electron emission control insulating film 32 may be such that the electric fields in adjacent small holes do not interfere with each other. The small holes 32a may be arranged at random, but from the viewpoint that electrons can be emitted more uniformly from the electron-emitting devices 39, it is preferable that the small holes 32a are arranged in a matrix form vertically and horizontally over the entire surface of the electron-emitting devices 39.

  More specifically, the size of the small hole 32a is, for example, a size that fits within a square having a side of 1 to 500 μm, and more specifically, an inner diameter of 5 to 300 μm. If the inner diameter of the small hole 32a is too small with respect to the layer thickness of the electron acceleration layer 33, the electric field in the small hole 32a tends to be weakened, and the electron emission efficiency tends to be lowered, and conversely, the inner diameter is too large. Then, the uniformity of electron emission tends to be impaired. For this reason, the inner diameter of the small hole 32 a is preferably 8.5 to 300 times the thickness of the electron acceleration layer 33. About 70 times is more preferable, and a specific numerical range is preferably 21.2-11.4 [mu] m (21-140 [mu] m when the third digit is rounded off). Here, the layer thickness of the electron acceleration layer 33 is preferably 0.3 to 2.0 μm as described later. Note that the size of the entire electron-emitting device 39 is, for example, a plane of several mm to several cm.

  On the other hand, the shape of the small hole 32a is not particularly limited. The planar view shape is, for example, a polygon (regular triangle, square, rectangle, rhombus, pentagon, hexagon, regular polygon, etc.), circle, ellipse, or the like. Among these shapes, a shape in which the ratio of the length of the major axis to the minor axis is preferably 1 to 2 in terms of not having a sharp apex where electrons tend to concentrate, and an ellipse that realizes this ratio is more preferable. Further, among these shapes, a circular shape that has the most gentle curvature when compared in the same area is more preferable.

  At this time, the cross-sectional shape in the film thickness direction of the small hole 32a is desirably rectangular or square so that electrons can be stably emitted in the vertical direction from the outer surface of the second electrode 3 of the electron-emitting device 39.

The small holes 32a are arranged in the electron emission control insulating film 32 at a density of 5 to 2000 / mm ² .

  In the present invention, the inner diameter of the small hole 32a is the length of the longest diagonal line in the case where the small hole has a circular shape in plan view, the diameter of a circle, the shape of an ellipse, the long diameter, and the polygon. Further, in the present invention, the short diameter of the small hole 32a is not only the short diameter when the planar view shape of the small hole is an ellipse (ellipse), but also the shortest when the planar view shape of the small hole 32a is a polygon. Including the length of the diagonal. The same applies to the long diameter. In the present invention, the long diameter of the small hole 32a includes the length of the longest diagonal line when the shape of the small hole 32a in plan view is a polygon. Here, when the planar view shape of the small hole 32a is a polygon, the shape formed by the photolithography process and the vertex having become circular arc shape is also included.

  If the size, shape, density, etc. of the small holes 32a are set such that the electric fields in the adjacent small holes 32a interfere with each other, the electron emission uniformity and controllability are impaired.

  As described above, the electron emission control insulating film 32 is an insulating film formed on the first electrode 2 and has a plurality of small holes 32a to uniformly control the electron emission of the electron-emitting device in the plane. It has a function.

  In addition to the structure of the present invention, a carbon thin film 34 is formed on the surface of the electron acceleration layer 33 on the second electrode 3 side.

  With this configuration, sufficient electrons can be emitted at an appropriate voltage, and dielectric breakdown is unlikely to occur, and continuous operation for a long time is possible. The carbon thin film 34 will be described in detail later.

Further, by providing a power source 37 that applies a voltage between the first electrode 2 and the second electrode 3 of the electron-emitting device 39, a sufficient amount of electron emission can be obtained by applying an appropriate voltage (for example, 10 to 25 V). At the same time, it is possible to emit electrons that can be stably operated continuously for a long time. The electron-emitting device has an electron-emitting function as a part of the ionization device. The electron-emitting devices, without discharge, without causing harmful substances, including ozone and NO _x, the long-term stability to the gas can be ionized.

  Note that the ionization apparatus of the present invention may include a plurality of electron-emitting devices. For example, a plurality of electron-emitting devices may be arranged on a plane body and applied to an ionization apparatus. Further, the first electrode 2 may be shared in a plurality of electron-emitting devices.

  Details of each element of the electron-emitting device 39 will be specifically described below. Note that elements having the same reference numerals as those of the electron-emitting device 1 of the first embodiment are the same as those of the electron-emitting device 39, and thus the description thereof is omitted.

<Electron emission control insulating film 32>
The electron emission control insulating film 32 is an insulating film formed on the first electrode 2 and has a function of uniformly controlling the electron emission of the electron emitting element 39 in the plane by having a plurality of small holes 32a. .

  The material and film thickness of the electron emission control insulating film 32, the size, shape, density, and the like of the small holes 32a are as described above.

<Electron acceleration layer 33>
The electron acceleration layer 33 includes the insulating fine particles 5 and is formed on the electron emission control insulating film 32 including the small holes 32a. This layer has a function of accelerating electrons from the first electrode 2 toward the second electrode 3.

  Since the electron acceleration layer 33 is mainly composed of the insulating fine particles 5, when a voltage is applied, a very weak current flows through the surface of the insulating fine particles 5 as described above.

  The voltage-current characteristic of the electron acceleration layer 33 shows a so-called varistor characteristic, and the current value is rapidly increased as the applied voltage increases. Part of this current becomes ballistic electrons due to the strong electric field in the electron acceleration layer 33 formed by the applied voltage, passes through the second electrode 3, and is emitted outside the electron-emitting device 39. Further, ballistic electrons may be emitted to the outside through the gaps (fine holes) of the second electrode 3 resulting from the influence of the irregularities on the surface of the electron acceleration layer 33 by the insulating fine particles 5.

  The formation process of ballistic electrons is presumed to be due to electrons tunneling while being accelerated in the direction of the electric field.

  Further, when the insulating fine particles 5 are completely dissolved and crystallized by heat treatment, the electron acceleration layer 33 becomes an insulator and loses the function of accelerating electrons, so that the second embodiment does not use conductive fine particles. In this configuration, it is not necessary to simply use the insulating fine particles 5 as a material, but it is necessary that the electron acceleration layer 33 be formed of the insulating fine particles 5 maintaining the particle shape.

  The film thickness of the electron acceleration layer 33 is preferably 0.008 to 6.0 μm, and preferably 0.3 to 2.0 μm, for example, when the applied voltage to the electron-emitting device 39 and the electron emission control insulating film 32 are in the above conditions. More preferred.

  If the electron acceleration layer 33 has a film thickness in the above range, it becomes easy to form the electron acceleration layer 33 having a uniform film thickness (smooth surface). As a result, the electron acceleration layer in a portion corresponding to each small hole 32a. The electric resistance value of 33 becomes uniform, and electrons can be emitted more uniformly over the entire electron-emitting device 39.

  The electron-emitting device 39 preferably accelerates electrons by applying a strong electric field at as low a voltage as possible. Depending on the voltage applied to the electron-emitting device 39, the thickness of the electron emission control insulating film 32, and the like, The film thickness of the electron acceleration layer 33 is preferably as thin as possible even within the above film thickness range (a range of 0.008 to 6.0 μm or 0.3 to 2.0 μm).

  The film thickness of the electron acceleration layer 33 refers to the thickness of the electron acceleration layer 33 (that is, the distance between the first electrode 2 and the second electrode 3) where the small holes 32a are formed.

As the insulating fine particles 5, insulating fine particles 5 made of a semiconductor oxide such as SiO ₂ or ZnO, or a metal oxide such as Al ₂ O ₃ , TiO ₂ , or CuO can be used. These insulating fine particles 5 can be used alone or in combination of a plurality of types.

  When a plurality of types of insulating fine particles 5 of different materials are used, the plurality of types of insulating fine particles 5 may be particles having a particle size in a numerical range described later.

  Further, when a plurality of types of insulating fine particles 5 are dispersed in a dispersion liquid and the dispersion liquid is applied on the electron emission control insulating film 32 to form the electron acceleration layer 33, the selection of the insulating fine particles 5 is performed in the dispersion liquid. It is desirable to consider the dispersibility of the particles.

  The particle diameter of the insulating fine particles 5 is preferably 5 to 1000 nm when the film thickness of the electron emission control insulating film 32 and the size of the small holes 32a are the above-mentioned conditions.

  If the particle size of the insulating fine particles 5 is smaller than 5 nm, it is difficult to reduce the variation in particle size, and it is difficult to form the electron acceleration layer 33 with a uniform film thickness. On the other hand, if the particle size is larger than 1000 nm, when the electron acceleration layer 33 is formed by applying a dispersion of the insulating fine particles 5, the insulating fine particles 5 settle in the dispersion and the dispersibility deteriorates. As a result, in the coating film of the dispersion liquid, it is easy to generate a portion where the insulating fine particles 5 are large and a portion where the insulating fine particles 5 are small.

  In the present invention, “particle size” means an average primary particle size.

  Furthermore, the electron acceleration layer 33 may contain a silicone resin as a binder component.

  By including the silicone resin in the electron acceleration layer 33, the mechanical strength of the electron-emitting device 39 can be improved, the device can be prevented from being deteriorated due to oxygen, moisture, etc. in the atmosphere, and the lifetime can be further improved. Can be achieved.

  Moreover, additives, such as a dispersing agent, may be contained in the electron acceleration layer 33 as needed.

  Further, the electron acceleration layer 33 may have a laminated structure of two or more layers made of different materials. For example, it is possible to adopt a laminated structure in which the first layer is a substantial electron acceleration layer 33, and the second layer is a protective layer for the purpose of increasing mechanical strength, moisture-proofing effect, and planarizing the film surface.

<Carbon thin film 34>
The carbon thin film 34 functions as a resistor between the second electrode 3 and the electron acceleration layer 33.

  Since the electron emission control insulating film 32 is provided with a plurality of small holes 32a as described above, when this electron-emitting device 39 is subjected to an aging test (for example, a continuous operation test for a long time), each small hole 32a. The state where the electric field is concentrated on the portion continues, and the electron-emitting device 39 is continuously exposed to local voltage / current stress.

  When a large voltage / current stress continues for a long time, defects may occur in the peripheral portion of the small hole 32a of the electron emission control insulating film 32, and when the number of defects increases, a current path is generated, leading to dielectric breakdown.

  Since the carbon thin film 34 as a resistor has a higher electrical resistance than the second electrode 3 made of, for example, gold, silver or the like, the local and continuous voltage / current stress applied by the electron-emitting device 39 is increased. As a result, defects are less likely to occur and dielectric breakdown is less likely to occur.

  As a material of the carbon thin film 34, for example, graphite is suitable.

  The film thickness of the carbon thin film 34 depends on conditions such as the applied voltage, the film thickness of the electron emission control insulating film 32, the size and density of the small holes 32a, the material of the second electrode 3, and the like. 5-20 nm is preferable. If the thickness of the carbon thin film 34 is less than 5 nm, it is not sufficient for the carbon thin film 34 to function as a resistor. On the other hand, if the thickness of the carbon thin film 34 is greater than 20 nm, the voltage required for electron emission becomes too large.

  In the second embodiment, an example in which the carbon thin film 34 is formed is shown, but the carbon thin film 34 may be omitted in the electron-emitting device 39. That is, the electron-emitting device 39 includes the first electrode 2, the electron emission control insulating film 32, the electron acceleration layer 33 including the insulating fine particles 5, and the second electrode 3 formed on the electron acceleration layer 33. May be provided. This also applies to the third embodiment described below.

[Embodiment 3]
The ionization apparatus according to the third embodiment will be described below with reference to the drawings.

  FIG. 3 shows a cross-sectional view of an electron-emitting device 49 constituting an ionization apparatus according to a third embodiment of the present invention. The ionization apparatus according to the third embodiment of the present invention is different from the second embodiment in that an electron emission element 49 is provided instead of the electron emission element 39. Other points are common to the second embodiment. Regarding the numbers of the elements constituting the electron-emitting device 49, the same reference numerals are given to the same elements as those in the electron-emitting device 39 of the second embodiment.

  In the second embodiment, the example in which the electron acceleration layer 33 is composed only of the insulating fine particles 5 is shown. However, in the third embodiment, the electron-emitting device 49 is replaced with the electron acceleration layer instead of the electron acceleration layer 33 in the second embodiment. 43.

  In addition to the insulating fine particles 5, the electron acceleration layer 43 includes conductive conductive fine particles 6 having a particle size smaller than that of the insulating fine particles 5.

  By adding the conductive fine particles 6 to the electron acceleration layer 43, it is possible to control the amount of electron emission of current flowing through the electron acceleration layer 43. In other words, the electric resistance value of the electron acceleration layer 43 can be adjusted to an arbitrary range by adjusting the content of the insulating fine particles 5 in the electron acceleration layer 43.

  Although it does not specifically limit as the electroconductive fine particle 6, For example, you may contain at least 1 sort (s) among the electroconductive particles which consist of gold | metal | money, silver, platinum, palladium, and nickel.

  If the particle diameter of the conductive fine particles 6 is equal to or larger than the particle diameter of the insulating fine particles 5, the insulating properties required by the electron acceleration layer 43 cannot be obtained. It must be smaller than the particle size of the fine particles 5.

  As described above, in the third embodiment, by applying the conductive fine particles 6 used in the first embodiment to the electron acceleration layer 43, the uniformity of electron emission and the spatial direction obtained in the second embodiment are obtained. Controllability can be obtained, and controllability of the current value electron emission amount obtained in the configuration of the first embodiment can be achieved. Thereby, uniform and highly controllable electron emission becomes possible, and an efficient ionization apparatus can be realized.

  An ionization apparatus according to the present invention includes at least an ionization unit including a chamber into which a sample gas is introduced, and an electron-emitting device provided facing the ionization unit, and the ionization unit into which the sample gas is introduced The sample gas is ionized from atmospheric pressure to medium vacuum by emitting electrons from the electron-emitting device.

  According to the above configuration, since the sample gas is ionized by the electron-emitting device, the possibility of alteration or deterioration of the sample material by active ions or radicals is low as in the conventional atmospheric pressure chemical ionization method (APCI). The electron adhesion phenomenon by energetic electrons can be used, and extremely soft ionization that is not possible in the past becomes possible. Specifically, unnecessary radicals are not generated and the sample material to be analyzed is less likely to be broken.

  In addition, if electron attachment by low-energy electrons is applied to proteins, the main chain of amino acids is preferentially fragmented, and the modified molecules remain bound to the main chain, which is effective in determining the modification site of the modified protein. Play.

  In addition, unlike the conventional atmospheric pressure chemical ionization method (APCI), there is no need to divide the ionization process into two stages and two chambers. In this application, both the sample gas and carrier gas are introduced and mixed before the ionization section. Can be ionized. That is, there is an effect that the structure and the process are simple.

  In addition, it is possible to emit electrons under almost the same conditions regardless of the state of the sample gas from atmospheric pressure to medium vacuum. Therefore, it can be performed at any pressure from atmospheric pressure to medium vacuum without major specification changes or adjustments. Can also be ionized with the same device, and has the effect of high versatility, applicability, and flexibility.

  In addition, since the sample gas in the atmospheric pressure state is ionized, a large number of molecules of the sample gas exist in the ionization section, so that the ionization efficiency is high, and the sample gas-derived ions are efficiently generated. In addition, since electrons can be emitted at atmospheric pressure, the gasification of the sample can be performed at atmospheric pressure, and the operability becomes easy. Even when the sample gas is in a medium vacuum state, the ionization efficiency is higher than in the high vacuum state, and the effect of efficiently generating ions derived from the sample gas is achieved.

  In addition, unlike the conventional atmospheric pressure chemical ionization method (APCI), there is no need to divide the ionization process into two stages and two chambers. In this application, both the sample gas and carrier gas are introduced and mixed before the ionization section. Can be ionized. That is, there is an effect that the structure and the process are simple.

  The voltage applied between the electron-emitting device and the counter electrode is preferably lower than the discharge start voltage of the sample gas.

  According to the above configuration, unlike the conventional atmospheric pressure chemical ionization method (APCI), there is a low possibility of sample material alteration or degradation by active ions or radicals. In this application, the number is lower than the discharge start voltage of the analysis gas. Since the electron attachment phenomenon due to low energy electrons of 10 eV or less is utilized, extremely soft ionization that has not been possible in the past becomes possible. Specifically, unnecessary radicals are not generated and the sample material to be analyzed is less likely to be broken.

  In addition, if electron attachment by low-energy electrons is applied to proteins, the main chain of amino acids is preferentially fragmented, and the modified molecules remain bound to the main chain, which is effective in determining the modification site of the modified protein. Play.

  In the electron-emitting device, a first electrode, an electron acceleration layer, and a second electrode are formed in this order, and a voltage is applied between the first electrode and the second electrode. It is preferable that electrons are emitted from the second electrode to the outside of the device.

  The electron acceleration layer preferably includes at least one of resin, insulating fine particles, and conductive fine particles.

  According to the above configuration, there is an effect that electrons can be obtained with extremely high efficiency as compared with atmospheric pressure photoelectron emission, which has been conventionally the only method for emitting electrons into atmospheric pressure.

  In addition, regardless of whether the sample gas is at atmospheric pressure or medium vacuum, electrons can be emitted under almost the same conditions, so ionization can be performed with this device without major specification changes or adjustments. The device is highly versatile, applicable, and has a high degree of freedom.

  In addition, when the electron acceleration layer contains conductive fine particles, the electric resistance value can be adjusted to an arbitrary range, the controllability of the current value electron emission amount is improved, and as a result, the ionization controllability is improved. Play.

  The mass spectrometer according to the present invention is characterized in that the sample gas ionized by the ionizer according to the present invention is introduced into a mass separation unit and a detection unit to perform mass spectrometry.

  According to the above configuration, mass analysis can be performed on highly efficient and highly accurate ions obtained by the ionization apparatus described above, and thus there is an effect that highly accurate mass analysis is possible.

  The ionization apparatus according to the present invention can be widely applied to all uses for ionizing an analysis gas and mass spectrometry for an ionized analysis gas.

DESCRIPTION OF SYMBOLS 1 Electron emission element 2 1st electrode 3 2nd electrode 4 Electron acceleration layer 5 Insulating fine particle 6 Conductive fine particle 7 Power supply 10 Ionizer 11, 12 Gas inlet 13 Gas outlet 14 Counter electrode 15 Ionization part 19 Pore 20 Mass Analyzing unit 21 Carrier gas 22 Sample gas 23 Exhaust gas 32 Electron emission control insulating film 32a Small hole 33 Electron acceleration layer 34 Carbon thin film 37 Power source 39 Electron emission element 43 Electron acceleration layer 49 Electron emission element

Claims (7)

An inlet for introducing a sample gas and an arbitrary carrier gas, an outlet for discharging generated ions to the outside, and an outlet provided separately from the outlet so that unnecessary exhaust gas can be discharged to the outside. An ionization part comprising a chamber having
And the electron-emitting device which is provided facing the ionization portion,
A counter electrode provided facing the ionization portion so as to face the electron-emitting device ;
A power source capable of applying a voltage between the electron-emitting device and the counter electrode ;
A voltage lower than the discharge start voltage of the sample gas is applied between the electron-emitting device and the counter electrode, and electrons are emitted from the electron-emitting device into the ionization portion into which the sample gas has been introduced. The ionization apparatus is configured to ionize the sample gas. Ionization apparatus according to claim 1, wherein the outlet for releasing the previous SL generated ions to the outside is characterized in that a pore. Ionization apparatus according to claim 1 or 2, characterized in that the ionization unit is the medium vacuum from atmospheric pressure. In the electron-emitting device, a first electrode, an electron acceleration layer, and a second electrode are formed in this order, and a voltage is applied between the first electrode and the second electrode. ionization apparatus according to any one of claims 1 to 3, characterized in that to emit electrons from the second electrode to the outside of the element by. The ionization apparatus according to claim 4 , wherein the electron acceleration layer includes at least one of resin, insulating fine particles, and conductive fine particles. The mass spectrometer which has an ionization apparatus of any one of Claims 1-5 . An ionization unit comprising a chamber having an introduction port for introducing a sample gas and an arbitrary carrier gas into the interior, a discharge port for discharging generated ions to the outside, and a discharge port for discharging unnecessary exhaust gas to the outside; and the ionization unit The sample gas is ionized using an ionization apparatus having an electron-emitting device provided facing the electron-emitting device and a counter electrode provided facing the ionization portion so as to face the electron-emitting device. And
After introducing the sample gas and an arbitrary carrier gas into the ionization part, a voltage lower than the discharge start voltage of the sample gas is applied between the electron-emitting device and the counter electrode, An ionization method, wherein the sample gas is ionized by emitting electrons from the electron-emitting device into the introduced ionization section.

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