CN108562550B - Frequency-stabilized optical cavity ring-down spectrometer for absolute measurement of carbon isotope content in atmosphere - Google Patents
Frequency-stabilized optical cavity ring-down spectrometer for absolute measurement of carbon isotope content in atmosphere Download PDFInfo
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- G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
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- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
- G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
- G01N21/39—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using tunable lasers
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- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
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- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
- G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
- G01N21/39—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using tunable lasers
- G01N2021/391—Intracavity sample
Abstract
The invention relates to a frequency stabilization method for absolute measurement of carbon isotope content in atmosphereA cavity ring down spectrometer, comprising: the ring-down optical cavity comprises a ring-down optical cavity, an air path system and an external optical path, wherein an air inlet hole and an air outlet hole are formed in the body of the ring-down optical cavity, and the air path system is connected with the ring-down optical cavity through the air inlet hole and the air outlet hole; the lasers of the first laser and the second laser in the external optical path are coupled in the ring-down cavity to form a TEM00 interference mode. The invention establishes CO measurement by using a frequency stabilization-based light intensity ring-down technology2Concentration and C13/C12Ratio instrument capable of realizing CO2The absolute measurement of the concentration does not need calibration, and the uncertainty is 0.057% -0.1%.
Description
Technical Field
The invention relates to a spectrometer, in particular to a frequency stabilization cavity ring-down spectrometer for absolute measurement of carbon isotope content in atmosphere.
Background
CO in the atmosphere2Mainly comes from the combustion of fossil fuels such as coal, petroleum and natural gas, the exhaust emission of motor vehicles and the CO in the atmosphere2Concentration of (2) 280ppm (10) before the industrial revolution-6The number of gas molecules contained in one million gas molecules) to about 400ppm at present, and CO is present in hundreds of years2The concentration of (c) increased by 40%. Atmospheric CO2 is mainly O16C12O16Natural abundance of 98.42%, the main isotope is O16C13O16The natural abundance was 1.106%. Accurate measurement of the CO2 isotope is vital to improve understanding of the global carbon cycle and CO2 source sink. Different emission sources have different isotope components, plant photosynthesis, respiration and fossil fuel combustion leave obvious CO2 isotope information in the atmosphere, and the isotope information also becomes an excellent tracer particle for researching carbon cycle. In addition to the application in the atmospheric carbon cycle, the isotope detection of the exhaled gas of the human body is used as a non-invasive medical diagnosis in medicine, such as the C13/C12 ratio in CO2 is used as a mark of the helicobacter pylori existing in the human body, so that the existence of the symptoms such as peptic ulcer and gastric cancer is predicted in advance.
The isotope ratio measurement technology mainly utilizes a mass spectrometry technology, is also a method mainly used at present, but has complex system structure and high cost, is difficult to realize real-time rapid measurement particularly in the field, and is difficult to popularize and apply in a large range. The laser absorption spectrum technology has the advantages of high sensitivity, high resolution, non-contact and real-time performance, and particularly, the development of semiconductor materials and the performance of photoelectric devices such as lasers, detectors and the like are greatly improved, the cost performance is improved, and the application of the absorption spectrum technology is greatly promoted. The spectrum analysis method mainly comprises a differential absorption spectroscopy (DOAS) technology, a tunable laser absorption spectroscopy (TDLAS) technology, a Direct Absorption Spectroscopy (DAS) technology and a cavity ring-down/cavity enhanced absorption spectroscopy (CRDS/CEAS) technology. The cavity ring-down absorption spectrum technology based on frequency stabilization enables light to be reflected for many times in a cavity due to a high-quality optical cavity, the effective absorption length can reach dozens of kilometers, the detection sensitivity is greatly improved, in addition, the cavity ring-down absorption spectrum technology can be measured in real time on site, a series of problems caused by sampling measurement are avoided, due to various advantages, the cavity ring-down absorption spectrum method based on frequency stabilization is a scheme which is internationally acknowledged to be most hopeful to solve accurate measurement of greenhouse gas components (the signal-to-noise ratio and the sensitivity are 3-4 orders of magnitude higher than those of the traditional method), and meanwhile, the cavity ring-down absorption spectrum technology can also be used for calibrating various concentration measuring.
However, most of the system is in the laboratory due to the complexity of the cavity ring-down system, and no mature cavity ring-down system capable of realizing accurate measurement exists.
Disclosure of Invention
The invention aims to provide a frequency-stabilized cavity ring-down spectrometer which can realize absolute measurement in atmosphere
The invention provides a frequency stabilization cavity ring-down spectrometer for absolute measurement of carbon isotope content in atmosphere, which comprises: the ring-down optical cavity comprises a ring-down optical cavity, an air path system and an external optical path, wherein an air inlet hole and an air outlet hole are formed in the body of the ring-down optical cavity, and the air path system is connected with the ring-down optical cavity through the air inlet hole and the air outlet hole; the lasers of the first laser and the second laser in the external optical path are coupled in the ring-down cavity to form a TEM00 interference mode.
Wherein the ring down cavity includes a first end and a second end.
The air inlet hole and the air outlet hole are positioned on the same side of the optical cavity body or on different sides of the optical cavity body.
The first end part of the ring-down cavity body is provided with a first high reflecting mirror, and the second end part of the ring-down cavity body is provided with a second high reflecting mirror.
The frequency stabilization cavity ring-down spectrometer is integrally positioned on the optical platform.
Wherein, further comprising a data acquisition processing unit.
The invention utilizes a frequency stabilization-based light intensity ring-down technology to establish an instrument for measuring CO2 concentration and C13/C12 ratio, and has the following main characteristics: 1. the instrument has simple structure, high detection sensitivity and good repeatability, and the measurement repeatability is less than 0.05%; (ii) a 2. Meanwhile, two beams of laser with the wavelength of 2.05 microns and 1.6 microns are utilized to construct interference in a TEM00 mode in an optical cavity, an absorption coefficient is obtained by simultaneously measuring a ring-down curve, and the concentration and isotope ratio of CO2 are further obtained; 3. the frequency modulation is realized by using an electro-optical modulator (EOM) to realize rapid scanning; 4. measurement of O16C12O16Has a characteristic spectral line of R (12) and an absorption center wavelength of 6237.421424cm-1Linear strength of 1.656 × 10S-23cm. Measurement of O16C13O16Characteristic spectral line of P10e, absorption center wavelength of 4879.276659cm-1Linear strength of S-8.270 × 10-24cm; 5. the absolute measurement of the concentration of CO2 can be realized, calibration is not needed, and the uncertainty is 0.057% -0.1%; the instrument can also be calibrated by using standard gas to realize relative measurement, the uncertainty level depends on the level of the standard gas, and the uncertainty is about 0.05 percent;
drawings
FIG. 1 is a schematic structural diagram of a frequency stabilized cavity ring down spectrometer of the present invention;
FIG. 2 is a schematic diagram of the structure of the ring down cavity of the present invention;
Detailed Description
To facilitate an understanding of the present invention, embodiments of the present invention will be described below with reference to the accompanying drawings, and it will be understood by those skilled in the art that the following descriptions are provided only for the purpose of illustrating the present invention and are not intended to specifically limit the scope thereof.
FIG. 1 is a schematic structural diagram of a frequency stabilized cavity ring down spectrometer of the present invention. As shown in fig. 1, the whole apparatus is divided into three main parts a, b and c, and the division of the three parts is not intended as a definition or a distinction between specific structures and components thereof, but is merely for convenience of understanding and description to help understanding the present invention.
The frequency stabilization cavity ring-down spectrometer comprises a ring-down cavity, a gas circuit system, an external light path and a data acquisition and processing unit, wherein the cavity ring-down spectrometer is integrally positioned on an optical platform so as to keep the high stability of the whole system.
The frequency stabilization cavity ring-down spectrometer comprises a digital time delay generator 1, a high-speed data acquisition card 2, a semiconductor laser controller 3, a microwave source 4, a first semiconductor laser 5 with the central wavelength of 1603.23nm, a second semiconductor laser 6 with the central wavelength of 2049.48nm, a first electro-optic modulator (EOM)7 of the first semiconductor laser, a second electro-optic modulator (EOM)8 of the second semiconductor laser 6, a first photoelectric detector 9 with the wavelength of 1600nm, a second photoelectric detector 10 with the wavelength of 2050nm, a mass flow controller 11, a pressure measuring unit 12, a vacuum pump 13, a temperature measuring and controlling unit 14, a lens 15, a first reflecting mirror 16, a second reflecting mirror 17 and a dichroic mirror 18; control system 19, ring down cavity 20.
FIG. 2 is a schematic diagram of a ring-down cavity. The ring-down cavity 20 includes a cavity body, the cavity body has an accommodating space therein, the cavity body has a first end and a second end, an air inlet is provided on a sidewall close to the first end, an air outlet is provided on a sidewall close to the second end, and the air inlet and the air outlet are located on the same side of the cavity body or on different sides of the cavity body. Inside the side wall in the extension direction of the optical cavity body there is a blind hole extending from the first end to the second end, said blind hole having a predetermined size, preferably said size being 20-60mm or other suitable size, preferably a platinum resistance thermometer or temperature sensor being arranged in said blind hole.
A first high reflecting mirror is arranged at the first end part of the optical cavity bodyThe structure of the first high reflector and the second high reflector can be the same or different according to specific design, preferably, the concave structure of the first high reflector is opposite to the concave structure of the second high reflector, the high reflectors are stuck on the end face of the cavity through epoxy resin and can be sealed on one hand, the blind hole is preferably 50mm deep, and the optical cavity body preferably adopts low thermal expansion coefficient (2 × 10)-7℃-1) The invar realizes the stability of the cavity length by external temperature control at 25.000 +/-0.003 ℃.
As shown in a part of fig. 1, the ring-down cavity is connected to a gas path system, the gas path system includes a gas path control unit and a temperature and pressure measurement unit, the gas inlet and the gas outlet of the ring-down cavity 20 are respectively connected to the gas path system through a pipeline, and the gas control unit controls the pressure and the quality of the gas entering the ring-down cavity 20. The temperature and pressure control unit controls the temperature and ambient pressure within the entire ring down cavity. The gas to be detected is controlled through a mass flow controller 11, the mass flow controller 11 is connected with the air inlet through a pipeline, the mass flow controller 11 is controlled through a control system 19, the control system 19 is preferably a PC or other control components, the gas to be detected enters the ring-down light cavity through the pipeline, the cavity pressure in the ring-down light cavity 20 is measured through a pressure measuring unit 12, in the working process, the cavity pressure is maintained at a preset pressure value or is adjustable within a preset pressure range, the cavity pressure is further preferably maintained at 100torr, an external vacuum pump 13 is connected to the outer side of an exhaust hole of the ring-down light cavity 20, and the vacuum pump 13 provides negative pressure for the ring-down light cavity 20; the temperature measurement unit 14 is connected to a standard platinum resistance thermometer in the blind hole for measuring the intracavity temperature of the ring down cavity 20.
As shown in parts b and c of fig. 1, two ends of the ring-down cavity 20 are respectively a first high reflecting mirror and a second high reflecting mirror, a dichroic mirror 18 is disposed outside the first high reflecting mirror, two beams of light split from the dichroic mirror 18 are respectively incident on a first photodetector 9 and a second photodetector 10, the first photodetector 9 and the second photodetector 10 are respectively connected to a digital delay generator 1, the first photodetector 9 and the second photodetector 10 are further connected to a high-speed data acquisition card 2, and the digital delay generator 1 is connected to a microwave source 4. The driver 3 of the semiconductor laser controls the first semiconductor laser 5 and the second semiconductor laser 6, the laser emitted from the first semiconductor laser 5 passes through the first electro-optical modulator 7, the laser emitted from the second semiconductor laser 6 passes through the second electro-optical modulator 8, passes through the first electro-optical modulator 7 and the second electro-optical modulator 8, the laser emitted from the first semiconductor laser 5 and the second semiconductor laser 6 passes through the lens 9, is emitted from the lens 9, is reflected by the first reflecting mirror 10 and the second reflecting mirror 11, and then illuminates the ring-down cavity 20, wherein the lens, the first reflecting mirror, the second reflecting mirror and other optical elements cooperate to couple the laser output by the two semiconductor lasers to the ring-down cavity 1, and a TEM00 interference mode is formed in the ring-down cavity 1.
The whole measuring device is divided into a ring-down cavity (comprising a high reflector), an external light path and a data acquisition and processing unit, the ring-down cavity at the core is shown in figure 1, the high reflector is respectively arranged at the left side and the right side, the specific parameters and the size are shown in figure 2, the unit is mm, the high reflector is adhered to the end face of the cavity through epoxy resin, on one hand, the high reflector can be sealed, on the other hand, the high reflector is used for forming intra-cavity interference, a blind hole with the depth of 50mm in figure 1 is used for placing a first-class platinum resistance thermometer, 1-2 are vent holes, wherein 1 and 2 are respectively a gas inlet and a gas outlet, and the low thermal expansion coefficient (2 × 10-7℃-1) The invar realizes the stability of the cavity length by controlling the external temperature at (25.000 +/-0.003) ° C
The schematic diagram of the optical path and the control system is shown in fig. 1, and the upper part a is an air path control unit and a temperature and pressure measurement unit. The inlet flow of the gas to be measured is controlled by a mass flow controller MFC, the pressure in the cavity is maintained at 100torr, and the negative pressure is provided by an external Pump; the middle b-th part is an optical path system; the following part c is the circuit control and signal measurement unit. All control and measurement signals can be automatically completed by a computer and are realized by a Labview program.
Laser light of about 1.6 microns and 2 microns output from the laser is coupled into the ring down cavity using lens 15 and mirrors 16,17 in fig. 1 and forms a TEM00 interference mode. When the voltage of the photoelectric detectors 9 and 10 reaches the threshold value, the time delay generator 1 is used for sending a cutting pulse to the microwave source 4 to cut off the light source, and the absorption coefficient alpha is obtained by measuring the absorption rate of photons in the ring-down cavity.
When a lean gas and a buffer gas are mixed, the absorption coefficient α can be given by:
α(v)＝n∑σi(v) (1)
where n is the particle number density of the rarefied gas, σiV is the frequency for the absorption cross section.
Still further, the absorption cross-section can be represented by the following formula:
σi(v)＝gi(v-vi)Sic (2)
wherein SiIs linear intensity, c is speed of light, gi(v-vi) Is a linear function and has the following normalized properties:
∫gi(v)dv＝1 (3)
by integrating equation (1), the area expression can be obtained as follows:
Ai＝∫αi(v)dv＝nSic (4)
for the two spectral lines measured by the instrument, the linear intensity is respectively S1.656 × 10-23cm and S8.270 × 10-24cm, central absorption wavenumber of 6237.421424cm-1And 4879.276659cm-1。
Measured area A combined with known linear intensityiAnd obtaining the molar concentration x of the gas to be detected and the isotope according to an ideal gas state equation:
wherein k isBAnd T and p are the Boltzmann constant, the gas temperature and the gas pressure, respectively.
Because the 1.6 micron laser and the 2 micron laser of the system work simultaneously and independently, the gas temperature and the gas pressure are the same, and the isotope ratio can be further obtained as follows:
the following description is only for understanding the working process of the cavity ring-down spectrometer of the present invention, and is not meant to be a unique limitation on the structure and working mode thereof, and those skilled in the art can make an adaptive adjustment with the structure of the spectrometer according to specific needs, and further improve the working steps thereof according to the adjusted structure, and the specific measurement and operation processes are as follows:
1. starting up and preheating, waiting for the temperature of the system to be stable, starting up the vacuum pump, and setting the pressure to be 100 torr.
2. The frequencies of the semiconductor lasers 5 and 6 of figure 1 are locked to the ring down cavity. By adjusting the working laser current, the TEM00 interference is respectively constructed in the optical cavity, and the frequency of the working laser is locked on the ring-down cavity by taking the number of ring-down as a target. When the voltages of the two detectors 9 and 10 reach the threshold voltage, a digital delay generator sends a cutting pulse to the microwave source 4 to cut off the light source, then a ring-down curve is recorded through a high-speed data acquisition card 2, ring-down time and absorption coefficient are obtained through fitting, and the ring-down time and the absorption coefficient are averaged after 320 times of measurement;
3. after measurement, the preliminary frequency modulation is realized by changing the control temperature of the working laser;
4. and repeating the step 2 to measure the absorption coefficient of the next frequency point, and averaging after 320 times of measurement.
5. Repeating the steps 3 and 4 to obtain the whole absorption spectrum, carrying out data processing by a Labview program,the area is obtained. The measured temperature T, total pressure p and the formula (5-6) are combined to obtain CO2Concentration and C13/C12A ratio.
The instrument is used for measuring the concentration of standard gas in a gas cylinder, wherein the gas is CO2And N2The mixture of (1) at a concentration of (400.25. + -. 0.20) ppm. The absorption spectrum is measured and fitted to obtain the area A, and the result is obtained by combining the formula (5):
table 1 shows CO2Uncertainty analysis meter
| C12O2 | C13O2 | C13/C12 | |
| Type A | |||
| Repeatability (%) | 0.01 | 0.01 | 0.01 |
| Uncertainty of fit (%) | 0.002 | 0.002 | 0.002 |
| Type B | |||
| Linear strength ur(S)(％) | 0.05 | 0.2 | 0.2 |
| Density ur(ρ)(％) | 0.01 | 0.01 | - |
| Isotope ur(x)(％) | 0.01 | 0.01 | - |
| Area ur(A)(％) | 0.006 | 0.006 | 0.006 |
| Free spectral range ur(FSR)(％) | 0.001 | 0.001 | 0.001 |
| Fitting residual ur(Residual)(％) | 0.001 | 0.001 | 0.001 |
| Standard uncertainty ur(％) | 0.054 | 0.20 | 0.20 |
The invention utilizes a frequency stabilization-based light intensity ring-down technology to establish an instrument for measuring CO2 concentration and C13/C12 ratio, and has the following main characteristics: 1. the instrument has simple structure, high detection sensitivity and good repeatability, and the measurement repeatability is less than 0.05%; (ii) a 2. Meanwhile, two beams of laser with the wavelength of 2.05 microns and 1.6 microns are utilized to construct interference in a TEM00 mode in an optical cavity, an absorption coefficient is obtained by simultaneously measuring a ring-down curve, and the concentration and isotope ratio of CO2 are further obtained; 3. the frequency modulation is realized by using an electro-optical modulator (EOM) to realize rapid scanning; 4. measurement of O16C12O16Has a characteristic spectral line of R (12) and an absorption center wavelength of 6237.421424cm-1Linear strength of 1.656 × 10S-23cm. Measurement of O16C13O16Characteristic spectral line of P10e, absorption center wavelength of 4879.276659cm-1Linear strength of S-8.270 × 10-24cm; 5. the absolute measurement of the concentration of CO2 can be realized, calibration is not needed, and the uncertainty is 0.057% -0.1%; the instrument can also be calibrated by using standard gas to realize relative measurement, the uncertainty level depends on the level of the standard gas, and the uncertainty is about 0.05 percent;
it is to be understood that while the present invention has been described in conjunction with the preferred embodiments thereof, it is not intended to limit the invention to those embodiments. It will be apparent to those skilled in the art from this disclosure that many changes and modifications can be made, or equivalents modified, in the embodiments of the invention without departing from the scope of the invention. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention are still within the scope of the protection of the technical solution of the present invention, unless the contents of the technical solution of the present invention are departed.
Claims (5)
1. A frequency-stabilized cavity ring-down spectrometer for absolute measurement of carbon isotope content in atmosphere comprises a ring-down cavity, a gas path system and an external light path, and is characterized in that a body of the ring-down cavity is provided with an air inlet hole and an air outlet hole, the outer side of the air outlet hole is connected with an external vacuum pump, the air inlet hole and the air outlet hole of the ring-down cavity are respectively connected with the gas path system through pipelines, and the body of the cavity adopts a low thermal expansion coefficient of 2 × 10-7℃-1The cavity length is stabilized by controlling the temperature of the outside to be 25.000 +/-0.003 ℃, a blind hole extending from the first end part to the second end part is arranged in the side wall of the optical cavity body in the extending direction, the size of the blind hole is 20-60mm, and a temperature sensor is arranged in the blind hole; the gas circuit system comprises a gas circuit control unit and a temperature and pressure measuring unit, and the gas circuit control unit controls the gas circuit to enter the ring-downThe pressure and the mass of the gas in the optical cavity, the flow of the gas to be measured is controlled by a mass flow controller MFC, the pressure in the cavity is maintained at 100torr, the negative pressure is provided by an external vacuum pump, and the temperature and pressure measurement unit controls the temperature and the ambient pressure in the whole ring-down optical cavity; the external light path comprises a first semiconductor laser with the center wavelength of 1603.23nm and a second semiconductor laser with the center wavelength of 2049.48nm, a first high reflecting mirror and a second high reflecting mirror are respectively arranged at two ends of the ring-down light cavity, a dichroic mirror is arranged on the outer side of the first high reflecting mirror, two beams of light split from the dichroic mirror are respectively incident to a first photoelectric detector and a second photoelectric detector, the first photoelectric detector and the second photoelectric detector are respectively connected to a digital delay generator, the first photoelectric detector and the second photoelectric detector are also connected to a high-speed data acquisition card, and the digital delay generator is connected to a microwave source; the driver of the semiconductor laser controls the first semiconductor laser and the second semiconductor laser, the laser emitted from the first semiconductor laser passes through the first electro-optical modulator, the laser emitted from the second semiconductor laser passes through the second electro-optical modulator, after passing through the first electro-optical modulator and the second electro-optical modulator, the laser emitted from the first semiconductor laser and the laser emitted from the second semiconductor laser pass through the lens, are emitted from the lens, are reflected by the first reflecting mirror and the second reflecting mirror, the reflected light is emitted to the ring-down cavity, and the lasers of the first semiconductor laser and the second semiconductor laser in the external optical path are coupled in the ring-down cavity to form a TEM00 interference mode; after the voltages of the first photoelectric detector and the second photoelectric detector reach the threshold value, a digital delay generator is used for sending a cutting pulse to a microwave source cutting light source, and an absorption coefficient is obtained by measuring the rate of absorption of photons in the ring-down cavity; measured area A combined with known linear intensityiAnd obtaining the molar concentration x of the gas to be detected and the isotope according to an ideal gas state equation:
wherein k isBT and p are respectively Boltzmann' S constant, gas temperature and gas pressure, SiLinear intensity, c is speed of light;
the first laser and the second laser work simultaneously and independently, the gas temperature and the gas pressure are the same, and further the isotope ratio is obtained as follows:
2. the frequency stabilized cavity ring down spectrometer of claim 1, wherein: the ring down cavity includes a first end and a second end.
3. The frequency stabilized cavity ring down spectrometer of claim 1, wherein: the air inlet hole and the air outlet hole are positioned on the same side of the optical cavity body or on different sides of the optical cavity body.
4. The frequency stabilized cavity ring down spectrometer of claim 1, wherein: the frequency stabilization cavity ring-down spectrometer is integrally positioned on the optical platform.
5. The frequency stabilized cavity ring down spectrometer of claim 1, wherein: further comprises a data acquisition and processing unit.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
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| CN201810300122.0A CN108562550B (en) | 2018-04-04 | 2018-04-04 | Frequency-stabilized optical cavity ring-down spectrometer for absolute measurement of carbon isotope content in atmosphere |
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| CN106483069A (en) * | 2015-08-26 | 2017-03-08 | 西安泰戈分析仪器有限责任公司 | Trace gas on-line analyses device based on cavity attenuation and vibration technique |
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