Study On The Precise Near-infrared Spectrum Of Second Overtone Transitions Of CO

Carbon monoxide(CO)is a common pollutant in the atmosphere,which is colorless,odorless and toxic to human body.It has a wide range of sources,mainly including automobile exhaust,coal combustion,etc.,which plays an important role in environmental monitoring and analysis.In order to achieve the accurate detection of CO,we need to obtain high-precision spectral data of CO.Cavity ring down spectroscopy(CRDS)is a kind of high-precision spectrum technology.It uses photodetector to measure the attenuation time of the light,not the absolute change of the light intensity,which is independent of the intensity and frequency of the light,and is not interfered by the change of the light source.Moreover,the actual equivalent absorption optical path can reach thousands of times because the incident light reflects back and forth many times in the cavity Kilometers or even tens of thousands of kilometers,greatly improving the sensitivity.The high resolution spectrum of CO can be obtained by CRDS.In order to obtain accurate spectral parameters,the most commonly used spectral line function Vogit line shape is no longer applicable.Considering the spectral line broadening mechanism such as collision narrowing effect and velocity dependent effect,it is necessary to select advanced line type to fit the spectrum respectively,compare the results,and select the most suitable line shape.In this experiment,CO gas with concentration of ?ppm1.0200 is selected for experimental analysis.Firstly,the absorption spectrum of CO in the second overtone(3 ?0)is measured by the cavity ring down spectrometer with stable cavity length,and the spectra of 41 lines under seven pressures are measured respectively.Then,we use five kinds of molecular linetypes to process and analyze the spectrum,and obtain 41 spectral parameters including collision broadening parameters and collision migration coefficient.We also know that under the experimental conditions,the fitting effect of SDRP linetype is very close to that of HTP linetype.Finally,the absorption intensity of molecular line is calculated by using the parameters obtained by multispectral fitting,and the line absorption intensity and collision broadening parameters are compared with the parameters in the three databases.The maximum percentage difference between the collision broadening parameters obtained by multispectral fitting and the HITRAN database is 2.61%,and the average relative uncertainty is 1.821%.The difference between the calculated linearabsorption intensity and the HITRAN database is not more than 4%,and the average average calculation uncertainty is 0.895%.