Laboratory measurements have been made of the absolute intensities of the discrete-line absorption band at 1.26 μ, and of the continuous bands at 1.26 and 1.065 μ in oxygen gas at pressures up to 4.3 atm. It has been shown that discrete and continuous absorptions are quite independent features, the one being a measure of the intrinsic transition probability in isolated molecules, the other of its enhancement in collision complexes. In the former the lines show significant pressure broadening, but the integral molecular absorption coefficients are constant; in the latter they are proportional to pressure and continuous absorption dominates in the 1.26-μ region at about ½ atm oxygen pressure. The radiative half-life of isolated 1Δg oxygen molecules is estimated to be 45 min, and the effect of gas pressure on the rate of decay has been predicted.

The electronic spectrum of calcium vapor has been photographed in absorption from 460 to 600 nm. A many line spectrum due to Ca2 has been identified from vibrational and rotational analyses and a total of 3800 lines involving 47 bands in the A1Σu+ ← X1Σg+ system of 40Ca2 have been assigned. Analysis shows that the X1Σg+ state is weakly bound with a dissociation energy De″ = 1075 ± 150 cm−1. The A1Σu+ state is considerably more stable. Term values, Dunham coefficients, and RKR potential energy curves have been determined for both electronic states, and Franck–Condon factors, with their dependence on rotation, have been evaluated. The more important constants for the ground state are ωe″ = 64.93 cm−1, ωexe″ = 1.07 cm−1, re″ = 0.4277 nm and those of the upper state are, [Formula: see text], [Formula: see text].Le spectre électronique de la vapeur de calcium a été photographié en absorption, de 460 à 600 nm. Un spectre de plusieurs raies provenant de Ca2 a été identifié à partir des analyses vibrationnelle et rotationnelle; on a déterminé les transitions correspondant à un total de 3800 raies appartenant à 47 bandes du système A1Σu+ ← X1Σg+ de 40Ca2. L'analyse montre que l'état X1Σg+ est faiblement lié, avec une énergie de dissociation

The 690 nm absorption spectrum of CF3NO has been studied in the gas phase at various temperatures and in the condensed phase at 77 K, and assigned to an (nπ*) transition. Analysis of the vibrational structure shows that, while only the eclipsed conformer is stable in the ground state, there are two stable isomers of comparable energy in the excited electronic state. One has an eclipsed conformation, but with the CF3 group tilted away from the oxygen atom. The other has a staggered conformation. In both of the excited state isomers the barrier to internal rotation is higher than in the ground state.

The rotational dependence of the Franck-Condon factors in the A-X system of Mg, has been calculated using R K R potential curves. Excellent agreement is found between theoretical and experimental intensity distributions.On a calcule I'influence de la rotation sur les facteurs de Franck-Condon, dans le systeme A-X de Mg,, en utilisant descourbes de potentiel RKR. L'accord entre les distributions d'intensite thtoriques et experimentales est excellent.

The electronic spectrum of cyclobutanone is examined to 78 100 cm−1. Nine electronic transitions are found, of which five form an ns Rydberg series leading to an ionization potential of 75 444 cm−1 (9.354 eV). The remaining four transitions are assigned in order of increasing energy as π* ← n, π* ← n′, Σco* ← n, and π* ← π. Earlier vibrational analyses of the first two of these are extended and corrected, and the excitation of the carbonyl stretch mode in the π* ← n′ transition is demonstrated. Vibrational analyses are also given for the structure observed in the π* ← π and Rydberg transitions. An analysis of existing data on the electronic and photoelectron spectra of acetone is used to support the general assignment of the second electronic transition of ketones as π* ← n′. Second and third ionization potentials of cyclobutanone are predicted to be about 11.70 and 13.34 eV.