Rotational analysis of the first negative band spectrum of oxygen

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Abstract
The first negative bands of oxygen, A 6856, (0, 2), A 6419, (0, 1), A6026, (0, 0), A 5632, (1, 0) and A 5295, (2, 0) appear in the negative glow when a discharge is passed through oxygen at low pressure. Under low dispersion the bands appear very diffuse, but each exhibits on the long-wave side a well-defined head degraded to the violet, to which the wave-lengths given above refer, accompanied by a less well-defined head about 30 cm.-1 towards shorter wave-lengths. Though they have no state in common with the ultra-violet negative bands they are generally attributed to the O j molecule. References to earlier work are given by Frerichs (1926), who excited the spectrum with high intensity in a hollow-cathode discharge in oxygen and photographed it in the first order of a 21 ft. grating. In each band he found two branches, one of which formed the sharp head referred to above. On the basis of a combination relation between the branches he assigned vibrational quantum numbers to the bands. Bands additional to those given above have been discovered by Mulliken and Stevens (1933) and Bozoky and Schmid (1935). It was found by the latter workers that the bands given above, with the exception of A6856, were not single but formed the first band in each of the progressions v' — v" = — 1, 0, +1, +2, respectively. They excited the spectrum by a high-frequency discharge which seemed to have a lower effective temperature than the hollow.-cathode discharge, so that the rotational structure was not well developed and the later bands in each progression were not masked by the overlapping rotational structure of the first band