Pressure effects on kinetics and decay processes in xenon after selective photoexcitation

Abstract

The decay dynamics of photoexcited rare gas cluster ions J. Chem. Phys. 111, 959 (1999); 10.1063/1.479378 A selected-ion-flow-drift-tube study of charge transfer processes between atomic, molecular, and dimer ion projectiles and polyatomic molecules ethane, propane, and n-butane Kinetics associated with the decay of the low-lying excited states of xenon is investigated in a density range 2.S X 10 18 to 2.S X 10 20 atoms cm -3 (pressure range between 10 4 and 10 6 Pa). Three different experiments are performed, i.e., two-photon excitation of 6p atomic states or ot molecular states, VUV one-photon excitation of the 6s[ 3/2] I and 6s' [ 112] I atomic states, and laser probing of intermediate transient species. The basic experimental data are the timeresolved second continuum excimer fluorescence at -173 nm and the photoionization current. It is found that all excitation decays through 6s[3/2] lor 6s[3/2Jz with a branching ratio 9/1. Part ofthe 6s[3/2] I species (70%) decay subsequently via the 6s[3/2Jz level. The effectiveness of these atomic intermediate steps is directly demonstrated by the transient laser probing. This result, the time analysis, and the discussion allow to set a clear basis to the involved processes and to rule out part of the models proposed in the literature. In particular, the hypothesis of infrared decay from attractive high-lying molecular states to the lowest lying excimer states 0: /6s[3/2] I and luOu-/6s[3/2]z is rejected. The data treatment, with the help of 2 or 2 X 2 exponential formula depending on density, is discussed. It takes into account the instrumental response so that kinetics information is reached down to the nanosecond range. In particular, the 0:, v::::::0/6s[3/2] I relaxed excimer lifetime is found to be 4.S(5) ns, and that ofthe lu,O; /6s[3/2Jz state 103(2)ns.

UV emission from excited inert-gas molecules

“…Кинетическая схема процессов с участием нижних 3 Р 1 , 3 Р 2 атомных уровней и молекулярных уровней ксенона приведена на рис. 4, а [38]. Эта работа продолжает исследования, выполненные в работе [39] (рис.…”

“…4. а -Схема кинетических процессов, исследуемых в ксеноне методом трехфотонного воз буждения [38] при возбуждении б -Упрощенная система термов ксенона, иллю стрирующая процессы распада при фотовозбуждении ксенона [39]. в -Упрощенная система термов криптона и основные каналы возбуждения и девозбуждения атома и молекулы криптона [40] Г.Н.…”

“…Этой тематике посвящено большое количество оригиналь ных работ и обзоров [10,38,78], к которым мы отсылаем читателя. К недо статкам этих работ следует отнести отсутствие какой либо информации о ВУФ излучении, без которой рассмотрение этой проблемы нельзя признать при емлемой.…”

Infrared emission spectrum and potentials of 0+uand 0+gstates of Xe2excimers produced by electron impact

“…We assume that they do not differ too much from those of the states responsible of the VUV continua. The radiative lifetime of highly excited vibrational states of the 0 + u and (1 u , 0 − u ) excimers is estimated to be τ 1 ≈ 5 ns [20] and τ 2 ≈ 40 ns [10], respectively. The decay rate for vibrational relaxation k 3 is the same for all states [23] yielding a decay time τ 3 = (k 3 N ) −1 ≈ 0.65 ns.…”

“…Metastable atomic-and g molecular states are mainly studied because of their importance for VUV emission [20]. The kinetics of the processes leading to excimer formation and VUV emission has been clarified in spectral and time resolved experiments, in which lifetimes and rate constants are determined [1,7,11,12,13,18,21,22,23,24,25,26].…”