Energy Transfer in the 2 <subscript> u </subscript> ( <superscript>1</superscript> D <subscript>2</subscript> ) Ion-Pair State of I <subscript>2</subscript> by Inelastic Collisions with Noble Gas Atoms.

We investigated the energy transfer in the 2 u ( 1 D 2 ) ion-pair state of I 2 by collision with noble gas atoms, Ar, Kr, and Xe, using an optical-optical double resonance/fluorescence detection technique. By analyzing the temporal profiles of the emission from the laser-excited 2 u ( 1 D 2 ) state at various noble gas pressures, the quenching rate constants were determined to be (4.55 ± 0.42) × 10 -10 , (4.23 ± 0.11) × 10 -10 , and (6.83 ± 0.16) × 10 -10 cm 3 molecule -1 s -1 for quenching by Ar, Kr, and Xe, respectively. The 2 g ( 1 D 2 ) ion-pair state, lying in the vicinity of the 2 u ( 1 D 2 ) state, was identified as a destination state by collision with Ar and Kr. Collision with Xe provided a new reactive pathway forming the excimer XeI( B ). The rate constants were determined to be = (9.61 ± 0.63) × 10 -11 cm 3 molecule -1 s -1 and = (4.87 ± 0.34) × 10 -11 cm 3 molecule -1 s -1 for the formation of the 2 g ( 1 D 2 ) state by collision with Ar and Kr, respectively, and = (6.55 ± 0.19) × 10 -11 cm 3 molecule -1 s -1 for the formation of XeI( B ). The collisional cross sections calculated from the quenching rate constants were considerably larger than the molecular size, owing to the harpoon mechanism.

Competing Interests: The authors declare no competing financial interest.

(© 2022 The Authors. Published by American Chemical Society.)