A study of infrared radiation of vibrationally excited CO in the 4.7 μm band and CO2 in the 4.3 μm and 2.7 μm bands

Abstract

A method is discussed suitable for the calculation of the spectral and integrated, over vibrational-rotational bands, radiation and absorption characteristics of diatomic and linear triatomic molecules in the absence of thermodynamic equilibrium between the vibrational and translational degrees of freedom. Radiation intensity I and black width eof CO2 molecules in the 4.3 μm and 2.7 μm bands, and CO molecules in the 4.7 μm band with a significantly excited degrees of freedom typical of molecular lasers have been calculated. By finding the logarithmic derivatives of the radiation intensity and black width of a band it has been shown to what degree I and e depend on pressure, optical path length and vibrational temperatures. It is demonstrated that the strongest effect on the radiation intensity of the vibrationally nonequilibrated molecular gas is exerted by the vibrational temperatures of the active (emitting) modes in a given band. This ensures a high accuracy and reliability in determining the vibrational temperatures of the thermodynamically nonequilibrated gas from the measurements of the IR-radiation intensity. It is shown with particular reference to a CO2 molecule that simultaneous measurements of the radiation intensity in the two vibrational-rotational bands, at 4.3 μm and 2.7 μm, make it possible to unequivocally find the vibrational temperatures of asymmetric stretching as well as combination modes of this molecule.