Selective obliteration of SF/sub 6/ molecules based on multiphoton absorption

The selective multiphoton excitation of vibrotational states of /sup 32/SF/sub 6 /species has been done by a pulsed CO/sub 2/ laser tuned at 948 cm/sup -1/. The Littrow grating arrangement with 100 lines/mm, 22/spl deg/ blazing angle is used to assure the laser bandwidth to be adequately less than the SF/sub 6/ isotope shifts (17 cm/sup -1/). The subsequent molecular dissociation occurs at high power densities. A FTIR spectrometer with 4 cm/sup -1 /resolution is employed to register characteristic peaks of /sup 32/SF/sub 6/ and /sup 34/SF/sub 6 /at 948 and 931 cm/sup -1 /respectively. The dissociation rate strongly decreases at higher pressures due to rapid deactivation of excited molecules based on momentum transfer of vibrational-translational process by collisional events between /sup 32/SF/sub 6/ and buffer molecules. Moreover the selectivity decreases at higher pressures, which mainly arises from vibrational-vibrational excitations of pertinent collisions among species to cause resonant obliteration of /sup 34/SF/sub 6 /molecules, consequently.