The collision-induced Cl2(D0u+ → Cl2(X) E0g+) transition Original Research Article

The dependences of the Cl2(D0u+,vD,JD→Cl2(X)g+E0g+,vE,JE) collisional induced transition rate constants on the vibrational vE,vD, rotational JE quantum numbers, energy gaps, and Franck–Condon factors of the combined levels have been studied in the range of vD=1–5. It has been shown that all the observed collisional induced intramolecular transitions (CIIT) are nonresonant and correspond to loss of up to 1100 cm−1 vibrational energy. The u↔g and ΔΩ=0 propensity rules are valid in the Cl2(D→Cl2(X)g+ion-pair states) CIIT. The vibrational and rotational distributions of the E state levels depend on vD number. For vD=3–5 the E state vibrational level corresponding to maximum Franck–Condon factor with the initial one is mainly populated. The E,vE=0,1,2; β1g,vβ=2; and E,vE=0 levels are populated from the D,vD=2 and 1 ones, respectively. The “ΔJ low” propensity rule is valid in the Cl2(D0u+,vD=1–5,JD→Cl2(X)g+E0g+,vE=1–5,JE and β1g,vβ=2,Jβ) CIIT. Rotational distribution of the vE=0 levels populated from the vD=1, 2 can be described as the Boltzmann one, T=300 K. The nonadiabatic transitions between potential energy surface corresponding to input Cl2(D)+Cl2(X) and output Cl2(E)+Cl2(X) channels occur in relatively short-lived collision complex, and CIIT rate constant is in the (0.4–3.2)×10−11 cm3/s range.