Kinetic measurements of fluorine, bromine and iodine atom-abstraction reactions at elevated temperatures by ground-state atomic rubidium, Rb(5(2)S(1/2)), studied by time-resolved laser-induced fluorescence

The kinetics of a range of halogen atom-abstraction reactions undergone by atomic rubidium in its electronic ground state, Rb(5(2)S(1/2)), have been i nvestigated by time-resolved laser-induced fluorescence at elevated tempera tures. Rb(5(2)S(1/2)) was generated in an excess of halogenated reactant an d He buffer gas by pulsed photolysis of rubidium halide vapours. Two separa te experimental systems were employed operating at the Rydberg transition a t lambda = 420.2 nm [Rb[6p(P-2(3/2))] --> Rb[5s(S-2(1/2))]} and at the shor ter wavelength component of the spin-orbit resolved D-line doublet transiti on at lambda = 780.0 nm (Rb[5s5p(P-2(3/2))] --> Rb[5S(S-2(1/2))]}. Second-o rder rate constants k(RX) for various F, Br and I abstraction reactions hav e been measured for essentially single-temperature conditions. These rate c onstants, which represent a new body of absolute rate data for Rb(S-2(1/2)) , are compared with the values reported hitherto by time-resolved atomic re sonance absorption spectroscopy and with those previously obtained for othe r alkali metal atoms using time-resolved techniques. (C) 2001 Elsevier Scie nce B.V. All rights reserved.