Kinetics of Growth and Decay of Excited Rare-Gas Atoms and Molecules in the Pulse Radiolysis of Pure Rare Gases and of Mixtures of Rare Gases With Molecular Quenching Agents

The temporal behavior of vibrationally relaxed first triplet Kr/sub 2/ in the presence of N/sub 2/ has been examined, and the rate constant for destructive quenching by N/sub 2/ has been evaluated at 298K. Its value is of the same order of magnitude as that for quenching of first triplet Ar/sub 2/, but is somewhat smaller. This suggests that the krypton and argon excimers excite different electronic states of N/sub 2/, the former leading to N/sub 2/(A) and N/sub 2/(B) and the latter principally to N/sub 2/(C), in accord with the general rule that near-resonant energy transfer tends to be favored over events which form products bearing significant translational energy. A new value for the spontaneous radiative decay constant of vibrationally relaxed first triplet Kr/sub 2/ has also been determined. A generalized mechanism for decay of Paschen(ls) atoms and for concomitant growth and decay of bound-state excimer molecules has been developed. Modelling calculations have shown that decay constants for Ar(/sup 3/P/sub 2/) measured at low (1 to 20 torr) and high (100 to 700 torr) pressures are not discrepant with respect to one another and can be precisely fitted with the generalized mechanism. Implications regarding the temporal behavior of vibrationally relaxed Ed/sub 2/ excimers are also discussed. Data obtained by single frequency laser probe monitoring of Ar(/sup 3/P/sub 2/) suggests that, although the ls-2p absorption lines are of Lorentzian form at 700 torr, as expected, the apparent line width narrows with increasing time. The cause of this phenomenon has not yet been identified