Energy losses of electrons in carbon monoxide and carbon dioxide

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In a previous paper published in these 'Proceedings' a report was given of some measurements on the energy losses suffered by electrons in nitrogen at pressures sufficiently low to ensure that practically only single collisions would take place. Electrons of homogeneous speed drawn from a hot cathode were fired through the gas and the velocity distribution in the emergent beam subsequently analysed by a combination of one longitudinal and one transversal electric field, the latter of a kind which would give refocussing of a slightly divergent incident beam at the entrance slit of the electron detector. The two most prominent characteristic energy losses observed in nitrogen were shown to be associated with energy levels known form the absorption spectrum of the nitrogen molecule in the far ultra-violet. The present investigation is an extension of this work to the two gases carbon monoxide and carbon dioxide. The former of these two was chosen as a typical diatomic gas, the energy levels of which are now fairly well known through the work of several investigators in recent years. Carbon dioxide was studied in addition to this, in view of the possibility that traces of this gas could have been formed from the carbon monoxide in contact with the hot cathode in the experiments with the latter gas. The experimental arrangements remained essentially the same as in the case of nitrogen. The tube was the one described in the previous paper referred to. The primary slit S 1 of sheet copper, which had been contaminated by mercury in the meantime when the tube was left standing without cooling the traps, was now replaced by a similar slit made of sheet silver. The cathode was coated with a mixture of barium and strontium oxides. As in the case of nitrogen all measurements were made with the gas continuously flowing through the apparatus, the pressure readings referring to the conditions in the tube through which the gas was admitted to the collision space.