Isotope effects in the quenching of electronically excited atoms. Part 4.—Quenching of I(52P½) by hydrogen and deuterium halides, H2O and D2O

Abstract

Spin-orbit relaxation of I(5²P_½) by the molecules H₂O, D₂O, HCI, DCl, HBr, DBr, HI and DI has been studied using time resolved atomic absorption spectrophotometry (λ= 206 nm; T= 293 K). It is concluded that quenching by the two most efficient molecules, H₂O and HBr, proceeds via resonant energy transfer channels (electronic → vibration + rotation) probably involving quadrupole–dipole coupling. However, the small isotope effects and relatively large cross-sections observed for the other molecules suggest that an efficient curve crossing mechanism dominates for HCI, DCI, DBr, HI and DI. This is consistent with other recent work involving Br(4²P_½) and the hydrogen halides.