The New Absorption System of Cyanogen Gas in the Near Ultraviolet. System I

Abstract

A new system of absorption bands has been found in the region λλ3020–2400 with an absorbing path of three meters and a pressure of two atmospheres. The gross structure of the system is comparatively simple. Two main progressions of bands with frequency differences 2050 cm—1 and 895 cm—1 have been found. The bands in these progressions can be accurately represented by a general formula: ν=A+ω1′v1′+x11′v1′2+ω2′v2′+x22′v2′2+x12′v1′v2′with A = 33,293.63, ω1′+x1′ = 895.75, ω2′ = 2065.38, x22′ = — 15.13 and x12′ = — 8.00. The electronic excitation is mainly at the C – N bond. The structure of the molecule in the excited state, its normal frequencies and symmetry properties are also discussed. The frequency difference 2050 cm—1 is considered as due to the totally symmetric longitudinal (C – N) vibration in the excited, state and a tentative assignment is suggested as follows: ν1′ = 895 cm—1, ν2′ = 2050 cm—1, ν3′ = 1770 cm—1, δ2′(u) = 210 cm—1. Other possible assignment has also been briefly discussed.