Physics of the aurora and airglow

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.

Absolute Intensities of the Discrete and Continuous Absorption Bands of Oxygen Gas at 1.26 and 1.065 μ and the Radiative Lifetime of the 1Δg State of Oxygen

An empirical technique is developed for obtaining the flux transmission, over a narrow spectral interval, of an assembly of layers of varying pressure and temperature. Although verified only for a regular spectrum of the type proposed by Elsasser (1942), the technique should be valid for any type of spectrum. Using this technique as a check, an empirical method of sufficient accuracy is developed for evaluating the integrated flux transmission of an assembly of layers. This latter method enables the radiation-chart procedures, advocated by Elsasser (1942), Robinson (1947), and Yamamoto (1952), to be tested for simply-stratified atmospheric models. Such tests reveal that the effects of temperature are inadequately taken into account. A principle advocated by Cowling (1950b) is developed into a radiation-chart procedure, in which the absorbing mass of each individual layer is corrected to a standard temperature and pressure. The coordinates of such a radiation chart are presented, but unfortunately adequate experimental data for the construction of such a chart are not yet available.

The evaluation of infra‐red radiative fluxes due to atmospheric water vapour

This monograph contains numerical tools required to compute approximately the effects of radiative transfer in the atmosphere for the far infrared region of the spectrum. We shall not deal with the transmission and scattering of solar radiation, but only with the long-wave radiation that is emitted, and of course also absorbed, by the earth’s surface, by clouds, and by the atmosphere itself. This part of the spectrum extends from a wavelength of about 4 microns to near the microwave range at a fraction of a millimeter wavelength. The main agents of transfer are two water-vapor bands and one band of carbon dioxide. In addition, there are some bands of carbon dioxide of minor importance and a band or rather a cluster of bands of ozone.

Gilbert N. Plass

Papers

The Effect of Pressure Broadening of Spectral Lines on Atmospheric Temperature.