Vacuum-Ultraviolet Absorption Spectrum of Carbon Suboxide

Abstract

Absorption coefficients of carbon suboxide have been measured from 2000 to 1050 Å photoelectrically and the absorption spectrum has been photographed from 1000 to 600 Å. The background light sources were the H₂, He, and Ar continua. The region from 1650–1050 Å is dominated by a ns←π Rydberg series converging to the first ionization potential at 10.60 eV. Diffuse structure on the short‐wavelength side of three of the Rydberg bands is probably caused by vibrational progressions in the C=C and C=O symmetric stretching frequencies but may be due to two other fragmentary Rydberg series. Several very strong diffuse bands are present below 1000 Å which have not yet been assigned. A system of 14 bands around 1780 Å may be a vibrational progression in a 400 cm⁻¹ bending mode or a vibrational sequence. Neither the experimental evidence nor theoretical considerations allow a definite assignment to be made. However, the gradual emergence of the vibrational structure from the underlying continuum strongly supports the progression explanation.