The approach-induced I 2( [formula omitted]) transitions, M=He, Ar, I 2, N 2, CF 4

Abstract

The dependencies of rate constant of the intramolecular I 2( E0 g + → M D0 u + ) approach-induced transition, M=He, Ar, I 2, N 2, CF 4, on the vibrational v E, v D, rotational J E, J D numbers, energy gaps, and Franck–Condon factors of the combined levels have been studied at nearly single-collision conditions by the OODR method. It has been shown that the observed approach-induced intramolecular transitions (AIIT) are nonresonant, correspond to loss of 100–700 cm −1 or gain of 160 cm −1 energy. For M≠CF 4 their cross-sections are independent of initial J E≈50–110 number and up to 60 (M=He) times less than maximum cross-section of the extremely long-range nearly resonant I 2( E,v E ↔ I 2( X) D,v D ) AIIT [Chem. Phys. 242 (1999) 263]. The nonresonant transition corresponding to loss of up to 160 cm −1 energy was found out for M=I 2, as well, but its cross-section is approximately nine times less than the maximum cross-section of the nearly resonant I 2( E,v E ↔ I 2( X) D,v D ) processes. The u↔g and ΔΩ=0 propensity rules are valid in the I 2( E)+M→I 2 (ion-pair states) + M AIIT. The vibrational and rotational distributions of the D state levels depend on the M nature. The J E dependence of the AIIT rate constant in the M=CF 4 case has been found out. For J E=110 rate constant is close to that of resonance approach-induced one, and the single rovibronic v D, J D≈110 level corresponding to loss of about 1290 cm −1 energy is populated. It has been shown that the data observed in this work and Chem. Phys. 242 (1999) 263 can be qualitatively explained in the framework of model of collision (approach) with large impact parameter.