Vacuum ultraviolet fluorescence from photodissociation fragments of CO and CO2

The vacuum ultraviolet fluorescence from photofragments of CO and CO2 has been studied and the cross sections for the production of fluorescence have been measured. The fragments were produced by interactions of the gases with synchrotron radiation in the wavelength region λλ175–800 Å. The dependence of the fluorescence intensity on gas pressure was studied and at high pressure additional fluorescence induced by photoelectrons was observed. Discrete features were observed in CO in the primary photon wavelength region λλ570–610 Å. Similar features were observed in CO2 in the λλ690–800 Å region corresponding to Rydberg states converging to the CO+2 (A 2Π) and CO+2 (B 2Σ+) states. The observed structure results from interactions of Rydberg states with dissociation continua. At shorter primary photon wavelengths the cross sections for the production of fluorescence from photofragments of CO decrease monotonically from 3.6 Mb at λ480 Å to 1.2 Mb at λ180 Å. In contrast with this, two broad bands were observed in the fluorescence from photofragments of CO2 with peak cross sections of 0.73 Mb at λ230 Å. The photodissociation and dissociative ionization processes that produce the observed results are discussed.