The optothermal spectrum of CDF3 mol. in the IR region was reported. Three strong absorption peaks were found at R(12), R(16) and R(26) lines. Among these, the absorption of R(12) and R(26) lines was overlapping the linear absorption spectrum. R(16) Line was a new peak which never appeared in the linear absorption spectrum and may be attributed to the different band of n5+ni琻i. The selective disociating of the mixture of CDF3 and CHF3 at the R(26) line of TEA CO2 laser was also observed The selective coefficient increased on adding buffer gas, Ar. It could be explained by reduction of the probability of collision between CDF3 and CHF3.

Key words: METHANE P, PHOTOCHEMISTRY, SPECTROGRAPHIC ANALYSIS, DMF, EXCITED STATE, CO2 LASER, FLUOROHYDROCARBON, LASER SPECTROMETRY, OPTOACOUSTIC SPECTROSCOPY, FOURIER TRANSFORM