Electronic to vibrational energy transfer from I(5 2P1/2). II. H2O, HDO, and D2O

Abstract

Time-resolved infrared fluorescence from I* (*=2P1/2) and vibrationally excited water has been observed following pulsed laser dissociation of I2 at 500 nm. The time dependence of the fluorescence signals has been used to determine the rates for the total quenching of I* by H2O, HDO, and D2O as well as for the vibrational self-relaxation of two modes of H2O and D2O. H2O and HDO are roughly 50 times more efficient in quenching I* than D2O. Analysis of relative fluorescence amplitudes shows that the quenching of I* by H2O and HDO is due entirely to an electronic-to-vibrational mechanism which produces two quanta of stretching vibration in the water molecule. The E→V mechanism is also likely to be the dominant mechanism for quenching of I* by D2O.

Quenching of I(2P�) by R-OH compounds. Influence of the alkyl group on the quenching efficiency

“…This strongly supports an E-v energy transfer process as the main channel for the I* deactivation and indeed, it has been directly observed [8].…”

“…A comparison of the quenching constant with those available in the literature is shown in Table I, where a good agreement is observed, especially with the four latest values reported. Burde and McFarlane [22] used the same experimental technique although a different precursor, while a time resolved infrared fluorescence determination was carried out by Grimley and Houston [8], and by Gonzalez Liz et al [17].…”

“…Few systems (HF, H 2 , and H 2 O) [5][6][7][8] have been studied directly (case a) because of the complexity added by the acceptor intramolecular energy redistribution which grows with the number of vibrational degrees of freedom. Based on the kinetic analysis of the system, state-to-state energy transfer studies are limited up to triatomic acceptor molecules.…”

Infrared Molecular Lasers Pumped by Electronic to Vibrational Energy Transfer.

“…hi Br ' + COB -Br + CCS (all states), (16) all cases, spontaneous emission from a particular species was almost completely blocked when a 2 cm cell Br' + CS,-Br . CS, (all 5tates), (17) containing this species was pLaced between the detector and the laser beam, indicating that the emitting tramiwere measured directly by monitoring Br ' fluorescence tion is (ool)-(000).…”

Vibrational Relaxation of H2O by H2, HCl, and H2O at 295K

“…Vibrational relaxation of water vapor has been studied by various techniques including laser-induced fluorescence (LIF), 1 ' 4 laser pump/probe, 5 E-eV transfer from electronically excited halogen atoms, 6,7 ultrasonic absorption and dispersion, 8,9 shock waves, 10 and H20 laser gain. 11 LIF measurements have provided detailed information on relaxation of and among the I, 2, 2,v2, and P 3 vibrational levels.…”