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The plasma generated by focusing a 20-Hz, 330-mJ, Nd:YAG laser pulse in a rare gas at pressures from 1 to 6 bars is proposed as a source of a VUV continuum giving as many as 10(9) photons nm(-1) sec(-1) near 170 nm. Its stability makes it suited to VUV spectrophotometry. The pulse duration, ranging from 20 nsec for Ne to 40 nsec for Kr, should also permit its use in time-resolved spectroscopy.

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...

Spectral, temporal, and density behavior of dye-laser-excited dense xenon below and above breakdown threshold has been studied. Observation of three-photon resonant excitation at 147 nm is limited to very low density (\ensuremath{\rho}7\ifmmode\times\else\texttimes\fi{}${10}^{16}$ atoms ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}3}$), whereas four-photon enhanced photoionization plays a major role between 500 mbar and 15 bar of pressure (1.4\ifmmode\times\else\texttimes\fi{}${10}^{19}$ to 40\ifmmode\times\else\texttimes\fi{}${10}^{19}$ atoms ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}3}$). Excitation and deexcitation schemes are discussed from existing data and our spectral and temporal results obtained from either excimer (172-nm continuum) or laser spark emission.

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.

The absorption spectrum of Xe2 has been studied with high resolution between 1290 and 1500 A, giving further information about the lower excited molecular states.

Between 160 and 230 nm, five band systems, including two new ones, have been recorded and classified by studying bismuth vapor produced in a heat pipe oven. They have been assigned to transitions from the X 1 Σ s + ground state of Bi 2 to high-lying Rydberg states converging to the 2 Π u 3 2 and 2 Π u 1 2 states of Bi 2 + at 7.53 and 8.94 eV. Some vibrational constants have been observed, by operating the heat pipe under unusual conditions.

Absorption spectra of high-density pure krypton and xenon gases, in the wavelength range 118-150 nm and the density range 1-80 amagat, exhibit a red shift of all the atomic lines. The shifts are interpreted by taking into account the high-density interactions with the help of the local field correction of Lorentz introduced in classical dispersion theory.

Bibliographical study of the principal experimental research of the last ten years on atomic and autoionization continua. We have restricted ourselves to the alkaline, alkaline-ferrous and rare gas groups. Moreover, with one exception, all the work cited is concerned with absorption spectra.We indicate the connections with theory and give the most important of the theoretical references.

A comparison of the dimensions of the trapping site in solid Xe, Kr, Ar and Ne to that in solid N2 leads to new assignments for the vibrational terms of the B3Σu−←X3Σg− transition of the oxygen molecule trapped in matrices. The anomalous shape previously found, in the argon matrix, for the potential energy curve of the excited state B3Σu− is corrected. The Lennard—Jones intermolecular potential parameters are derived for this excited state.

The ultraviolet spectra of CS 2 and OCS trapped in a rigid matrix have been observed. The possibility of appearance of Rydberg transitions is discussed in terms of the dimension of the excited orbital and the matrix lattice.

Several absorption spectra are presented which were taken in the spectral range 2600-1050 A with atoms (Hg, Xe), radical (H) and molecules (CO, N 2 , NO) in pure solid form or trapped in solid rare gas matrices at temperatures between 20 and 1.5°K. Shifts of resonance lines of Hg and Xe are compared with those obtained under high pressure in gaseous state. The fourth positive group of CO and the Lyman-Birge-Hopfield bands of N 2 are perturbed in the pure solid but not in matrices. The intensity of the w 1 Δ u ← X 1 Σ g + transition of N 2 is enhanced in the pure solid but not in matrix and the progression is observed up to v ′ = 17. Rydberg states disappear in solid dilute NO and vibrational spacings of the valence states become regular as the perturbating interactions of the two types of states no longer exist.

An experimental setup including the synchronized coupling of a VUV spark source with a laser is described. Experimental results on the depletion of Ar(2), Kr(2), and Xe(2) excimer fluorescence illustrate the capability of the system.

A simple experimental arrangement allowing multistep excitation studies including one VUV photon as the first excitation step is described. The system is based on the simultaneous use of a monochromatized VUV-laser plasma source with a tunable dye laser. The same pump laser is used for both excitation sources, thus allowing, if required, a well-defined time delay between the two excitation steps. The system permits both photoionization and time-resolved fluorescence measurement. Its capability is illustrated by experiments on rare gases. This demonstration shows that such a device allows one to obtain spectroscopic and kinetic information.