%0 Journal Article %T Calculation of the Absorption Cross Sections of Some Molecules from GEISA Database at the Wavelengths of Isotopically Different CO2 Lasers %A Asylkhan Rakhymzhan %A Alexey Chichinin %J ISRN Analytical Chemistry %D 2013 %R 10.1155/2013/592971 %X 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. 1. Introduction In this paper we report molecular absorption cross sections at CO2-laser emission frequencies for several selected gases of atmospheric relevance (M£¿=£¿NH3, C2H4, CO2, O3, NO2, PH3, HNO3, SF6, CH3OH, HCOOH, OCS, CH3CN, C2H6, SO2, and H2O). This information may be useful mainly in the differential absorption (Light Detection and Ranging) LIDAR technique for remote measurement of the gas species [1¨C8] and also may be used to monitor the CO2 content in fuel combustion products [9], remote sensing of gases in human breath [10], or multiphoton dissociation processes or to measure water vapor concentration and wind speed vector in the plume of volcano [11, 12]. Note that the LIDAR technique sometimes is used for remote sensing of some exotic gases, like, for example, chemical warfare [13]. In some cases (CH3OH and HCOOH) it also may be used in designing optically pumped FIR (far infrared=THz) lasers where CO2 laser is used as a source of a pump radiation [14]. Also, the absorption of CO2-laser radiation by a cell with a mixture of some of these gases is used in our lab for quick check and assignment of the CO2-laser lines. The focus of the present study is to predict absorption cross section in pure air at wavelengths of seven isotopic CO2 lasers: 12C16O2 (normal), 13C16O2, 12C18O2, 14C16O2, 14C18O2, 13C18O2, and 12C16O18O, which we hereafter denote as 26-, 36-, 28-, 46-, 48-, 38-, and 268-lasers. In the clear atmosphere, absorption at 9¨C11£¿¦Ìm is due primarily to water vapor and carbon dioxide. Since the fraction of CO2 %U http://www.hindawi.com/journals/isrn.analytical.chemistry/2013/592971/