Vibrational relaxation of CO+(A2.PI.i), CS(A1.PI.), and C2(A3.PI.g) in helium

Abstract

Publication costs assisted by the Department of DefenseNonequilibrium vibrational distributions of CO+(A2n,u'=0-6), CS(A1rI,u'=&5), and Cz(A3TI,u '=M) were prepared by collisional processes in a 300-I< helium flowing-afterglow apparatus. The vibrational band intensities of the electronic emission systems were used to obtain the steady-state vibrational distributions from 0.8 to 15 torr. Extensive vibrational relaxation by collisions with He was observed for CO"(A) and CS(A), but not for C,(A), over this pressure range, Electronic quenching of CS(A) probably is competitive with vibrational relaxation, even in helium. The data were fitted to relaxation models based upon Au = 1 collisional transitions by using the steady-state master equation formulation. The Au = 1 relaxation cross sections for CO+(A) and CS(A) with He are in the range of 0.01 of the gas kinetic values. The upper limit to the 4 u = -1 relaxation cross section for C,(A) is 5 X of the gas kinetic value. Studies of the relaxation of CS(A'n) in Ar were attempted, but electronic quenching appeared to dominate over vibrational relaxation. These results are compared to vibrational-translational relaxation of other electronically excited states.

Luminescence of excited fragments produced from methyl halides in noble gas flowing afterglow

“…Concerning the formation mechanism of these neutral excited species, it may occur via an electron recombination reaction, analogous to the reaction of He(23S) and CS2 (14). Another possible process is dissociative excitation of the reagent molecule.…”