J.-L. Subtil

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

Kinetics associated with the decay of the low‐lying excited states of xenon is investigated in a density range 2.5×1018 to 2.5×1020 atoms cm−3 (pressure range between 104 and 106 Pa). Three different experiments are performed, i.e., two‐photon excitation of 6p atomic states or 0+g molecular states, VUV one‐photon excitation of the 6s[3/2]1 and 6s’[1/2]1 atomic states, and laser probing of intermediate transient species. The basic experimental data are the time‐resolved second continuum excimer fluorescence at ∼173 nm and the photoionization current. It is found that all excitation decays through 6s[3/2]1 or 6s[3/2]2 with a branching ratio 9/1. Part of the 6s[3/2]1 species (70%) decay subsequently via the 6s[3/2]2 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...

Pressure effect on 6p-6s ir decay in xenon after two-photon excitation

Abstract Pressure effects on the decay rates of the Xe 6p[ 1 2 ]0 (0–800 mbar) and 6p[ 3 2 ]2 (0–200 mbar) levels have been measured up to 6 × 108 s−1 using two-photon excitation. An analysis in terms of binary and ternary total quench rates for both transitions is presented. A radiative lifetime of 28.2 ± 0.5 ns has been found for both 6p[ 1 2 ]0→6s[ 3 2 ]01 (828.0 nm) and 6p[ 3 2 ]2→6s[ 3 2 ]02 (823.2) transitions.

Wannier excitons in liquid and solid krypton

Abstract Combining near-normal incidence and oblique incidence (70°) reflection spectra in liquid krypton with dispersion analysis, a hitherto not reported band at 11.205 eV is shown to be the n = 2Γ( 3 2 ) exciton, with the reduced effective mass of 0.29±0.06. The results on the solid (grown in a closed cell, at a temperature near the triple point) are in full accord with those reported from absorption spectroscopy at 20 K under stringent ultrahigh vacuum conditions.

Time- and energy-resolved luminescence of the KrAr exciplex: from the dilute to the condensed phase

Abstract The relaxed 0 + ( 3 P 1 ) and 1 ( 3 P 2 ) Kr * Ar exciplex luminescence was observed in dense Ar samples doped with small amounts of Kr (1–5 ppm). The use of selective vacuum ultraviolet excitation, temporally and spectrally resolved luminescence allowed us to fully resolve these emissions. The density dependence of the [1,0 − ] ( 3 P 2 ) relaxed exciplex radiative lifetime was determined continuously from the gas to the liquid. The radiative lifetime extrapolated to zero density was found to be 230 ns.

Xenon luminescence in high pressure argon : spectroscopy and kinetics

Abstract The luminescence associated with selective excitation of the three lowest xenon resonant levels (3P1/6s[ 3 2 ]01, 1P1/6s′[ 1 2 ]1 and 5d[ 3 2 ]01) in high pressure (14–71 bar) argon doped with minimal amount of xenon is reported. Under these conditions the decay channels specific to Xe*Ar were obtained without Xe*2 formation. In particular, it is demonstrated that the part of the 3P1 level excitation population which is not radiated “immediately” is first transferred to the 3P2 metastable level. Subsequently a long 3P1 decay also occurs via its formation by the reverse reaction. An analogous behavior is found for the upper 1P1/3P0 levels showing that most of the fluorescence is retarded with in this case transfers of population to the close 6p[ 1 2 ]1 and to 6s(3P1/3P2) levels. The behavior found after 5d[ 3 2 ]1 level excitation is quite diferent, with in parallel a fast direct fluorescence and a quenching into the 1P1/3P0 levels but not directly into the 3P1/3P2 levels. A kinetic analysis is developed according to these schemes. Particularly, the 3P1 to 3P2 quenching is found to depend linearly on the density with the rate k2=(4.5±0.5) × 10−13 cm3 s−1. The more complicated description of the 1P1 clearly indicates the necessity of using selective excitation to succeed in a self-consistent interpretation.

1P1 level decay in high pressure krypton

The 1P1 decay in high pressure krypton (densities 1×1020–5×1020 cm−3 ) has been investigated using selective photoexcitation. At densities above 4×1020 cm−3, the decay occurs fully through the 3P1 level. 1P1 blue or red excitation lead to identical results with evidence of a long lived reservoir effect with a rate constant associated with 1P1→3P1 transfer of ≊0.2×10−32 cm6 s−1. The kinetic scheme includes formation of short distance g symmetry excimers followed by 1g dissociation into the 3P1 state. At low density the results strongly support the hypothesis of a competing O+g(1P1) infrared excimer decay into the relaxed 1u(3P2) state.

Xenon atomic-like 3P2 radiative decay in cold and high-pressure argon

Abstract The decay channels of Xe * ( 3 P 2 ) in low-temperature and high-pressure argon gas doped with ppm levels of Xe are reported. At low temperatures the argon perturbed Xe * ( 3 P 2 ) decays radiatively in addition to the decay channel observed at room temperature, i.e. through 3 P 1 by means of endothermal collisions. The lifetime of the argon perturbed Xe * ( 3 P 2 ) is found to be several microseconds. The nature of the emitting level is discussed.