Photolytic spectroscopy of simple molecules. I. The production of 5 ²D atoms from Cs₂

A two-photon technique is reported for the measurement of relative cross sections for the selective photolysis of simple molecules into particular product channels. In a demonstration of this method two independently tunable dye lasers were used to sequentially dissociate molecules of Cs₂ for wavelengths in the visible range and then to excite the resulting products to Rydberg states which could be readily ionized for detection. With this system the spectra were determined for the selective photolysis of Cs₂ into product atoms in the 5 ²D_3/2 and 5 ²D _5/2 states. Two relatively broad absorption bands were found, each of which led to the preferential population of a different fine structure components of the 5 ²D products. Analysis of the photolysis spectra indicated that both dissociation and predissociation mechanisms were responsible and led to the identification of a new ¹Σ_u and ³Σ_u state correlated with the 5 ²D atomic states.