Calculation of the Absorption Cross Sections of Some Molecules from GEISA Database at the Wavelengths of Isotopically Different CO2 Lasers

A calculation of the absorption cross section of some molecules (NH3, C2H4, CO2, O3, NO2, PH3, HNO3, SF6, CH3OH, HCOOH, OCS, CH3CN, C2H6, SO2, and H2O) at the wavelengths transmitted by a CO2 laser filled with different isotopes (12C16O2, 13C16O2, 12C18O2, 14C16O2, 14C18O2, 13C18O2, and 12C16O18O) is presented. The spectroscopical parameters for the molecules from GEISA database have been used. Hence the selection of the molecules was substantially based on the availability of the parameters in the database. The results of the calculations may be used in designing the differential absorption technique for remote monitoring of these molecules. The pressure and temperature dependence of the cross sections are described by and coefficients; these coefficients were calculated for the largest absorption cross sections for each molecule. The absorption cross sections of CH3OH and HCOOH at low pressures for all these CO2 lasers are also presented. These calculations are provided for design of new CO2-laser-pumped far-infrared lasers.