CN111398404A - Cross molecular beam experimental device with independently tunable collision angle and detection angle - Google Patents
Cross molecular beam experimental device with independently tunable collision angle and detection angle Download PDFInfo
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- CN111398404A CN111398404A CN202010410854.2A CN202010410854A CN111398404A CN 111398404 A CN111398404 A CN 111398404A CN 202010410854 A CN202010410854 A CN 202010410854A CN 111398404 A CN111398404 A CN 111398404A
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/62—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating the ionisation of gases, e.g. aerosols; by investigating electric discharges, e.g. emission of cathode
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- G—PHYSICS
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- H—ELECTRICITY
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- H01J49/00—Particle spectrometers or separator tubes
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J49/00—Particle spectrometers or separator tubes
- H01J49/26—Mass spectrometers or separator tubes
Abstract
The invention discloses a cross molecular beam experimental device with independently tunable collision angle and detection angle. The invention simultaneously configures a relatively fixed molecular beam source and a molecular beam source with an angle capable of being tuned through the transmission connecting rod in the rotatable beam source preparation cavity, and efficiently and conveniently realizes the independent tuning of the collision angle between the two beam sources and the angle of the two beam sources relative to the detector under the condition of not damaging vacuum. When the detection angle is changed, the concentricity between the preparation cavity of the rotatable beam source and the reaction/detection cavity is ensured by adopting a large-size high-precision bearing, and the dynamic sealing performance is realized by adopting the matching of a spring rubber ring and a differential pumping system. Through the series of designs, the cross molecular beam experimental device is suitable for researching the velocity distribution of the same chemical reaction product under different collision energies under various detection angles.
Description
Technical Field
The invention relates to a cross molecular beam experimental device, in particular to a cross molecular beam experimental device with independent and continuous tuning of a collision angle and a detection angle.
Background
The cross molecular beam technology is an important tool for realizing the elementary chemical reaction research of quantum state resolution in modern physical chemistry experimental research. The so-called cross molecular beam technique is to make two molecular beam sources perform single collision under a high vacuum environment at a certain angle, and then elastic/inelastic scattering or chemical reaction process occurs. In a specific experimental research process, kinetic information such as energy distribution, product spatial distribution and the like of elementary chemical reactions are differentiated according to different collision energies, so that capturing the micro dynamic change information under different collision energies is one of important subjects for researching one elementary chemical reaction.
The experimental apparatus for elementary chemical reaction research based on cross molecular beam technology generally realizes the change of collision energy by changing the collision angle or the speed of reactant molecules in the molecular beam. The prior cross molecular beam experimental device is usually provided with a plurality of beam source cavities, one beam source cavity corresponds to a fixed collision angle, and the switching between the collision angles can be realized only by disassembling and replacing the beam source cavity after the cavity is opened to destroy the vacuum. Even so, based on the consideration of the manufacturing cost, one experimental set can only configure the beam source cavity corresponding to the conventional collision angle such as 45 degrees and 90 degrees.
In order to realize experimental studies at more collision angles, researchers need to dope a rare gas in a gas for preparing a molecular beam source so as to change the final speed of the molecular beam to realize the purpose of changing collision energy. However, the final velocity of the molecular beam source is only changed by the change of the mass of the doping gas and the ratio thereof, since the species of the rare gas is limited, and when the doping ratio is too large, the detection signal will be rapidly attenuated due to the dilution of the reactant molecules in the molecular beam source. It follows that continuous adjustment of the final speed of the molecular beam source, i.e. a change in the collision energy, cannot be achieved by doping with a noble gas.
On the other hand, in order to capture kinetic information of energy distribution, product space distribution and the like of the elementary chemical reaction, the product velocity distribution under 0-180 degrees corresponding to the centroid coordinate system needs to be measured, and then information of product space distribution, product energy distribution and the like of the product under the full angle is deduced. In order to achieve the research purpose, the conventional cross molecular beam experimental device adopts a mass spectrometry detection technology, a commercial mass spectrometer is installed in a mass spectrometry detection cavity with a tunable angle, a product velocity distribution diagram is measured at a certain angle, and product information under a full angle is obtained by combining a numerical fitting method. Because the mass spectrum detection region can ensure the signal-to-noise ratio of an experiment only by working in an ultrahigh vacuum environment, the mass spectrum detection cavity must be provided with a multistage differential vacuum pumping system and can be cooled by combining with liquid nitrogen, thereby meeting the vacuum degree requirement of the mass spectrum detection region. According to the design scheme, the volume of the mass spectrum detection cavity becomes extremely complex and large, and the reaction/detection cavity which needs to accommodate the whole mass spectrum detection cavity becomes large, so that the manufacturing cost is greatly increased. In addition, the mass spectrometer is a high-precision detection tool, and an external power controller and a signal controller need to be kept relatively static with the mass spectrometer so as to prevent the instability of signals caused by slight pulling of a connecting wire. However, this is extremely inconvenient in implementation and stability cannot be fully ensured.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides the cross molecular beam experimental device with the collision angle and the detection angle capable of being independently and continuously tuned.
The technical scheme adopted by the invention for realizing the purpose is as follows:
the invention mainly comprises a rotatable beam source preparation cavity and a reaction/detection cavity.
The rotatable beam source preparation cavity consists of a rotatable chassis, a first beam source cavity and a second beam source cavity, and the interior of the rotatable beam source preparation cavity is vacuumized by a first vacuum pump arranged at the bottom of the rotatable chassis so as to realize and maintain the vacuum degree required by beam source preparation.
The pulse valves in the first beam source cavity can be rotationally adjusted around the circle center of the rotatable chassis through the transmission connecting rod, so that the tuning of the relative angle α between the two pulse valves, namely the tuning of the collision angle between the reactants, is realized.
The reaction/detection cavity consists of a vacuum square cavity and a detector, wherein the vacuum square cavity is vacuumized through a second vacuum pump to maintain the vacuum requirement required by experimental research, the vacuum square cavity is connected and positioned with a rotatable chassis through two high-precision bearings, the rotatable chassis is driven by a chain wheel to rotate by using a cavity central shaft of the vacuum square cavity, namely, a shaft where an original point of an experimental coordinate system is located, so that the change of a relative angle β between two molecular beam sources and the detector, namely the change of a detection angle is realized, and the dynamic sealing performance between the rotatable chassis and the vacuum square cavity is maintained through a differential pumping system between a spring rubber ring and an O ring groove in a plurality of O ring grooves on the side surface of the vacuum square cavity.
The invention has the following advantages and beneficial effects: according to the invention, through introducing the design of the rotatable chassis and the transmission connecting rod, on the premise of not damaging vacuum, on one hand, the independent tuning of the collision angle between molecular beams is realized, so that the experimental research of chemical reactions under different collision energies is met, the experimental operation flow is greatly simplified, and the time cost is saved. On the other hand, the angle tuning between the two molecular beams relative to the detector is realized to meet the measurement of product speed distribution under different detection angles, and the change of the detection angle is realized without rotating the detector, so that the stability of the high-precision detector is ensured.
Drawings
FIG. 1 is a schematic structural view of the present invention;
FIG. 2 is a top view of the present invention;
the device comprises a rotatable chassis, a first beam source cavity, a second beam source cavity, a first vacuum pump, a pulse valve, a transmission connecting rod, a high-precision bearing, a spring rubber ring, a differential pumping system, a chain wheel, a vacuum square cavity, a spring rubber ring, a differential pumping system, a chain wheel, a vacuum square cavity, a second vacuum pump, a detector and a detector, wherein the rotatable chassis is 1, the first beam source cavity is 2, the second beam source cavity is 3, the second beam source cavity is 4.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and examples.
As shown in fig. 1 and 2, the present embodiment mainly includes a rotatable beam source preparation chamber and a reaction/detection chamber.
The rotatable beam source preparation cavity is composed of a rotatable chassis 1, a first beam source cavity 2 and a second beam source cavity 3 and is used for preparing a reactant, namely a molecular beam source, for chemical reaction research, the interior of the rotatable beam source preparation cavity is vacuumized by a first vacuum pump 4 installed at the bottom of the rotatable chassis 1 so as to realize and maintain the vacuum degree required by beam source preparation, the first beam source cavity 2 and the second beam source cavity 3 are fastened with the rotatable chassis 1 through screws and are positioned in cooperation with bolts so as to avoid secondary position calibration during repeated disassembly and installation, a pulse valve 5 is respectively installed inside the beam source cavity and is used for preparing an ultrasonic molecular beam with a single quantum state as a reactant for chemical reaction research, the installation positions of the two pulse valves are both aligned to the circle center of the rotatable chassis 1, namely the original point under an experimental coordinate system, so as to ensure the effective cross collision area of the two molecular beams, and the pulse valve 5 of the beam source cavity 2 can be rotatably adjusted around the circle center of the rotatable chassis 1 through a transmission connecting rod 6 so as to realize the tuning of the relative angle α between the two pulse valves 5 and.
The reaction/detection cavity consists of a vacuum square cavity 11 and a detector 13, the reaction/detection cavity is a place where two molecular beam sources generate single collision to trigger chemical reaction and detect the velocity distribution of a product, the vacuum square cavity 11 is vacuumized by a second vacuum pump 12 to maintain the vacuum requirement required by experimental research, the vacuum square cavity 11 is connected and positioned with the rotatable chassis 1 by two high-precision bearings 7, the rotatable chassis 1 is driven by a chain wheel 10 to rotate by a cavity central shaft, namely a shaft where the origin of an experimental coordinate system is located, so that the relative angle β between the two molecular beam sources and the detector is realized, and the dynamic sealing performance between the rotatable chassis 1 and the vacuum square cavity 11 is maintained by a differential pumping system 9 between a spring rubber ring 8 and an O ring groove in three O ring grooves on the side surface of the vacuum square cavity 11.
In this embodiment, the vacuum pump is a magnetic suspension molecular pump, and is hermetically connected with the chamber wall through a knife-edge flange, wherein the rotatable beam source preparation chamber is equipped with the magnetic suspension molecular pump with pumping speed of 1600 l/s, and the reaction/detection chamber is equipped with the magnetic suspension molecular pump with pumping speed of 2200 l/s.
In the embodiment, the surfaces of the three O-ring grooves are subjected to mirror polishing, the surface roughness reaches about 0.4 μm, and the effect of dynamic sealing is ensured.
In this embodiment the detector 13 is a mass spectrometer detector.
In the embodiment, a relatively fixed beam source and a beam source with an angle capable of being tuned through a transmission connecting rod are simultaneously arranged in the rotatable beam source preparation cavity, so that the collision angle α between the two beam sources and the angle β of the two beam sources relative to the detector can be efficiently and conveniently tuned under the condition of not breaking vacuum, the concentricity between the rotatable beam source preparation cavity and the reaction/detection cavity is ensured by adopting a large-size high-precision bearing when the detection angle is changed, the dynamic sealing performance is realized by adopting the matching of a spring rubber ring and a differential pumping system, and the cross molecular beam experimental device is suitable for researching the velocity distribution of the same chemical reaction product under different detection angles under different collision energies through a series of designs.
The specific operation process of this embodiment is as follows:
1. the open cavity fixes the positions of the two beam source cavities on the rotatable chassis, and two pulse valves are arranged to be aligned with the circle center of the preparation cavity of the rotatable beam source.
2. The chamber cover is closed, all the vacuum pumps and the differential pumping system are started, so that the vacuum degree of each part in the chamber reaches 10-8In torr order, baking the cavity wrapping the detector and adding liquid nitrogen to make the vacuum degree of the detection area better than 10-11torr amountAnd (4) stages.
3. The collision angle between molecular beam sources can be calculated according to the collision energy required by experimental research, the angle of a transmission connecting rod is manually adjusted outside a rotatable beam source preparation cavity, the position of a pulse valve which is connected with the beam source preparation cavity is changed, and the angle between the pulse valve and another pulse valve which is relatively fixed is made to accord with the calculated collision angle.
4. Two pulse valves and detectors are opened.
5. The whole rotatable beam source preparation cavity is driven by a chain wheel to rotate around the central axis of the cavity so as to change the angles of the two molecular beams relative to the detector, the product velocity distribution under each angle is collected at equal intervals within 0-180 degrees corresponding to a centroid coordinate system, and finally the dynamic information such as product energy distribution, spatial angle distribution and the like is obtained.
In conclusion, the invention can efficiently and conveniently adjust the collision angle between two molecular beam sources and the detection angle relative to the detector through the outside mechanical without opening the cavity to destroy the vacuum, thereby obtaining the velocity distribution information of the same chemical reaction product under different collision energies under different detection angles.
The above embodiments are only for illustrating the technical idea and features of the present invention, and the purpose of the embodiments is to enable those skilled in the art to understand the contents of the present invention and implement the present invention, and not to limit the protection scope of the present invention. All equivalent changes and modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.
Claims (5)
1. The cross molecular beam experimental device with independently tunable collision angle and detection angle comprises a rotatable beam source preparation cavity and a reaction/detection cavity, and is characterized in that:
the rotatable beam source preparation cavity consists of a rotatable chassis (1), a first beam source cavity (2) and a second beam source cavity (3), and the inside of the rotatable beam source preparation cavity is vacuumized by a first vacuum pump (4) arranged at the bottom of the rotatable chassis (2) so as to realize and maintain the vacuum degree required by beam source preparation;
the ultrasonic molecular beam source comprises a first beam source cavity (2), a second beam source cavity (3), a transmission connecting rod (6), a pulse valve (5) and a rotary base plate (1), wherein the pulse valve (5) is respectively arranged in the first beam source cavity (2) and the second beam source cavity (3) and used for preparing an ultrasonic molecular beam with a single quantum state as a reactant for researching chemical reaction, the installation positions of the two pulse valves are both aligned to the circle center of the rotary base plate (1), namely the original point under an experimental coordinate system, and the effective cross collision area of the two molecular beam sources is ensured;
the reaction/detection cavity is composed of a vacuum square cavity (11) and a detector (13), wherein the vacuum square cavity (11) is vacuumized through a second vacuum pump (12) to maintain vacuum requirements required by experimental research, the vacuum square cavity (11) is connected and positioned with a rotatable chassis (1) through two high-precision bearings (7), the rotatable chassis (1) is driven by a chain wheel (10) to rotate by a cavity central shaft of the vacuum square cavity (11), namely an axis where an original point of an experimental coordinate system is located, change of a relative angle β between two molecular beam sources and the detector is realized, namely change of a detection angle, and dynamic sealing performance between the rotatable chassis (1) and the vacuum square cavity (11) is maintained through a spring rubber ring (8) in a plurality of O ring grooves in the side surface of the vacuum square cavity (11) and a differential pumping system (9) between the O ring grooves.
2. The apparatus of claim 1, wherein the collision angle and the detection angle are independently tunable, and the apparatus comprises:
the first beam source cavity (2), the second beam source cavity (3) and the rotatable chassis (1) are fastened through screws and are positioned by matching with bolts, so that secondary calibration of positions is not needed when the device is repeatedly disassembled and assembled.
3. The apparatus of claim 1, wherein the collision angle and the detection angle are independently tunable, and the apparatus comprises:
the first vacuum pump (4) and the second vacuum pump (12) are both magnetic suspension molecular pumps and are in sealing connection with the corresponding cavity walls through knife edge flanges, wherein the pumping speed of the first vacuum pump (4) is 1600 liters per second, and the pumping speed of the second vacuum pump (12) is 2200 liters per second.
4. The apparatus of claim 1, wherein the collision angle and the detection angle are independently tunable, and the apparatus comprises:
the O-ring grooves are divided into three, the surface of each O-ring groove is subjected to mirror polishing, the surface roughness reaches 0.4 mu m, and the effect of dynamic sealing is ensured.
5. The apparatus of claim 1, wherein the collision angle and the detection angle are independently tunable, and the apparatus comprises: the detector (13) is a mass spectrometry detector.
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| CN202010410854.2A CN111398404A (en) | 2020-05-15 | 2020-05-15 | Cross molecular beam experimental device with independently tunable collision angle and detection angle |
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| CN202010410854.2A CN111398404A (en) | 2020-05-15 | 2020-05-15 | Cross molecular beam experimental device with independently tunable collision angle and detection angle |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113295763A (en) * | 2021-06-03 | 2021-08-24 | 浙江师范大学 | Cross molecular beam detection device capable of eliminating interference of reactant background signals |
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2020
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113295763A (en) * | 2021-06-03 | 2021-08-24 | 浙江师范大学 | Cross molecular beam detection device capable of eliminating interference of reactant background signals |
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