Pressure effects on kinetics and decay processes in argon under selective photoexcitation

• Published in: The Journal of chemical physics 1987-10, Vol.87 (8), p.4576-4588
• Main Authors: MOUTARD, P, LAPORTE, P, SUBTIL, J.-L, DAMANY, N, DAMANY, H
• Format: Article
• Language: English
• Subjects: Atomic and molecular physics; Atomic properties and interactions with photons; Exact sciences and technology; Intensities and shapes of atomic spectral lines; Physics
• ISSN: 0021-9606; 1089-7690
• DOI: 10.1063/1.452869

Kinetics associated with the decay of low lying excited states of argon is investigated in a pressure range up to 4×106 Pa. Selective pulsed vacuum-ultraviolet excitation is used for the first time for a kinetic study of argon allowing a rather detailed analysis. The results are deduced from time resolved total luminescence of the well-known second continuum which is associated with the lowest excimer states 0+u(3P1) and 1u, 0−u(3P2), having fast and slow radiative decays, respectively. A different ratio of the fast to the slow component is observed when exciting in the high or in the low energy side of the first self-broadened line, the 1S0→3P1 transition centered at 106.6 nm, quite similar to what has been reported for xenon. The kinetic model introduced by Wenck et al. for xenon [Chem. Phys. Lett. 66, 138 (1979)] is the only one that agrees with the observed time and pressure dependences. In this model, the decay of the atomic state 3P1 leads to efficient population of 1u, 0−u(3P2), via 0+u(3P1), and 1g, 0−g(3P2), molecular states and the atomic state 3P2. The radiative lifetime of the (1u, 0−u) excimer state is presently determined to be 3.15(5) μs. The decay associated with 1P1 excitation is more complicated since it involves more intermediate steps. No difference is detected when exciting in the low or in the high energy side of the corresponding self-broadened line. That result, together with the time behavior, allows one to conclude that the atomic state 3P0 is efficiently populated in the decay sequence, thus introducing a rather long lived reservoir effect. Such an effect is totally different from what was reported for xenon in which collision coupling with the nearby 6p levels plays a major role.