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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.

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.