Ultra-violet emission bands associated with oxygen

Abstract

Of emission band spectra generally attributed to oxygen the best known is the negative band spectrum with four strong heads at λλ6420-6300; λλ6010- 5960; λλ5630-5550; λλ5290-5200. In addition there are several other fainter bands about λλ5900-5840; λλ6790-6700; λ6200; λ4980, etc. This spectrum appears with considerable intensity in the yellowish-white glow surrounding the negative electrode of a discharge tube containing pure oxygen, while at lower pressures it is visible along the capillary of the tube. The diffuse character of the bands under the dispersion of an ordinary prism spectrograph renders such wave-length determinations of little value however, except as serving for identification of the bands, and they do not appear to have been measured under high dispersion. The spectrum has been investigated by numerous observers, and although it has not been found in absorption there is general agreement that it arises from an oxygen molecule. In the far ultra-violet (λλ1830-1920) Schumann, using a fluorite spectrograph, was the first to obtain emission and absorption bands of oxygen. These bands were investigated in some detail by Steubing (loc. cit.), who confirmed Schumann's observations and showed that the system consists of some five bands extending from λλ1831—1845; λλ1848—1863; λλ1864—1881; λλ1882—1899; λλ1900-1919. Each head consists of about eleven lines giving the appearance of being degraded to the red; and the most refrangible head is the strongest of the five. He was also able to excite in this region the fluorescence spectrum of oxygen. It was found to coincide in position with the emission bands, though the intensity distribution in the spectrum was somewhat different. The two less refrangible heads, it should be mentioned, were observed in fluorescence only. The bands were attributed by him to an O₂ molecule and this appears to have been accepted by later workers; though Kayser took exception to these views.