Studies of the Photoproduction of Electrons in Inert Solid Matrices. The Electronic Spectrum of the Species C2−

Abstract

The vacuum‐ultraviolet photolysis of acetylene isolated in an argon matrix at 14°K in the presence of a small concentration of a photoelectron source leads to a marked enhancement in the intensity of the 5206‐Å band system previously assigned to the Swan transition of C₂. Cesium atoms have been found to provide an especially abundant electron source for these studies. The vibrational band spacings observed for the 5206‐Å band system agree much more closely with those recently reported by Herzberg and Lagerqvist for the 5416‐Å band system of a species tentatively identified as C₂⁻, produced upon flash discharge through methane, than with the band spacings observed in the gas phase for the Swan transition of C₂. Accordingly, it is suggested that the 5416‐Å band system of the gas‐phase studies and the 5206‐Å band system of the argon‐matrix experiments correspond to the same transition. The enhancement of this band system in the presence of a photoelectron source supports the hypothesis that the species which contributes it is negatively charged.