Temperature dependence of self- and N 2-broadeningand pressure-induced shifts in the 3←0 band of CO

Abstract

A variable-temperature single-pass absorption gas cell with an optical pathlength of 147.5 cm was designed and built for spectroscopic measurements of gases of atmospheric interest. The cell is optically matched to a Bomem DA8.3 Fourier transform spectrometer. A heating/cooling system enveloping the cell, used together with a Neslab ULT-80 thermal bath, allows spectroscopic studies of gas samples at temperatures ranging from 205 to 350 K and at pressures up to 1 atm. Tests of the optical, thermal, and vacuum operation of the system were performed. Spectra of the 3←0 vibrational–rotational band of carbon monoxide were recorded from 225 to 348 K and used to determine the rotational gas temperatures. These results were compared with values obtained using thermocouples, in order to assess the thermal performance of the new system. A second temperature-controlled cell 25-cm long, able to withstand pressures up to 30 atm, was also used to record CO spectra. We have recorded high-resolution FTIR spectra of CO and CO perturbed by N 2 at temperatures from 295 to 348 K. The spectra were analyzed to determine pressure broadening and pressure-induced shift coefficients, along with their temperature dependence for several transitions in the second overtone band of CO. The results, especially for self-broadening, are in excellent agreement with other recent measurements reported in the literature.