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.