The quasi random model is one of the elementary models of molecular band absorption. We show its application in the interaction of a free electron laser beam of wavelength 4mm with high resolution lines of the sulphar dioxide gas. The frequency interval considered is from 2523.336 to 2524.727 cm-1. Values of transmittance, averaged over intervals of 0.1 cm-1, are calculated for absorber thickness 0.05, 0.5 and 5 atm-cm by the help of quasi random model. From generated absorptance values intensities of the high resolution absorption lines in the above interval of SO2 can be simulated. The application prospect of this work in atmospheric optics is quite bright.
