Photodissociation of positive ions. I. Photodissociation spectra of D+2, HD+, and N2O+

The operation of an apparatus constructed to measure absolute photodissociation spectra of ions and to determine the kinetic energy spectrum of the photoproducts by time-of-flight analysis is described. Photodissociation spectra for the processes D+2+hν→D++D and N2O+→NO++N have been obtained, and the photodissociation cross sections for HD++hν→H++D and HD++hν→D++H have been measured. The photodissociation spectrum of D+2, using an irradiation bandwidth of <0.05 to 0.1 nm, is in reasonable agreement with the structureless spectrum of von Busch and Dunn obtained with a 20 nm bandwidth. The two possible photoprocesses in HD+ were observed to have the same cross sections 2×10−19 cm2 at 589 nm. The photodissociation spectrum of N2O+ over the range 295–342 nm was found to be very sharply structured, with σNO+ =2.6×10−18 cm2 for the largest peak, at 338.5 nm. Fifteen peaks in the N2O+ spectrum were assigned to vibrational progressions in the ? 2Σ←? 2Π1/2,3/2 transition. In making the assignments it was necessary to assume the ions possess from 0 to 2 quanta in the degenerate bending mode, leading to Renner effect splitting in the 2Π state.