The “approach-induced” and collision-induced I2(E0g+→ I2(X)D0u+) transitions from low, vE=8–23, vibronic levels of the I2(E) state Original Research Article

The dependences of the I2(E0g+,vE,JE→I2(X)D0u+,vD,JD) transition rate constants on the vibrational vE,vD, rotational JE,JD quantum numbers, energy gaps, and Franck–Condon factors of the combined levels have been studied in the range vE=8–23. The extremely long-range near-resonance I2(E,vE→I2(X)D,vD) process as well as nonresonant transitions, corresponding to the energy loss up to ΔE=240 cm−1 (approximately three quanta of vibrational energy), have been observed. Total cross-section of the latter is up to 12 times less than the maximum one of the extremely long-range transition. It has been shown that cross-sections of the processes are independent of initial JE number. The u↔g and ΔΩ=0 propensity rules are valid in the I2(E)→I2(X)I2 (ion-pair states) transitions. The vibrational and rotational populations of the D state levels depend on vE and ΔE. Mechanism of the processes under study has been discussed. It has been shown that essentially nonresonant transitions occur after a mutual I2(E) and I2(X) capture in orbiting-controlled collision complex. Maybe, one has to take into account relativistic (magnetic) interactions for description of the extremely long-range transitions.