Non-adiabatic transitions between first tier ion-pair states of I2 induced by collisions with Ar atoms

Abstract

Non-adiabatic transitions from the I2(E0g+, D0u+, β1g and D′2g) states to first tier ion-pair (IP) states induced by collisions with Ar atoms have been investigated. The stepwise laser excitation schemes have been used for selective population of close-lying vibronic states: E, vE=13, D, vD=18, β, vβ=19 and D′2g, vD′=23. Rate constants of population of the first tier ion-pair states from the optically populated rovibronic states as well as rate constants of depopulation of the states have been determined. Analysis of the mechanism of the transitions has been carried out.We find that the λlummax≈3410Å luminescence band in the case of optical population of the D and β states cannot be described assuming the collision-induced non-adiabatic transitions only. We conclude that there is an additional radiative channel for population of the states, probably, due to the formation of the ArI2(IP) van der Waals complexes.