Reactions of ground state atomic rubidium at elevated temperatures investigated by time-resolved laser induced fluorescence [Rb(5(2)P(3/2)-5(2)S(1/2)); lambda=780 nm]

We present a kinetic investigation of atomic rubidium in its 5s(S-2(1/2)) e lectronic ground state, generated by pulsed irradiation of rubidium halides , and monitored by time-resolved laser induced fluorescence (LIF) using the D-line transition at lambda = 780 nm [Rb(5(2)P(3/2) - 5(2)S(1/2))]. LIF de cay profiles for Rb(5(2)S(1/2)) were recorded at different total pressures with mixtures of various reactants (R) of fixed relative composition f = [R ]/([R] + [He]) with excess He bath gas at elevated temperatures. The follow ing absolute second-order rate constants k(R)(cm(3) molecule(-1) s(1)) are reported for the reaction of Rb(5(2)S(1/2)): N2O, (5.1 +/- 0.2) x 10(-11) ( 875 K); CF3Cl, (1.1 +/- 0.1) x 10(-11) (875 K); CF2Cl2, (1.1 +/- 0.1) x 10( -11) (875 K); CFCl3, (2.2 +/- 0.1) x 10-11 (877 K); CH2Cl2, (8.9 +/- 0.2) x 10(-12) (875 K); CHCl3, (1.1 +/- 0.1) x 10(-11) (876 K); CCl4, (1.4 +/- 0. 4) x 10(-11) (876 K). These data are compared principally, where possible, with analogous data for reactions of Cs(6(2)S(1/2)), generally obtained by time-resolved atomic resonance absorption spectroscopy, following pulsed ir radiation. To the best of our knowledge, we believe the present investigati on to be the first study of these rate processes with the halide reactants by LIF.