Ultraviolet photodissociation of Xe2+ and Kr2+ 1(12)u: Detection of rare-gas dimer ions in real time

Momentary depletion of the Xe2+ (or Kr2+) 1(12)u population is observed by photodissociating the molecule at 351.1, 337.1, or 307.9 nm [on the 1(12)u2(12)g band] and monitoring the temporally resolved emission from the dissociative-recombination-fed neutral Xe line at 828.0 nm (6p[12]06s[32]1). Near total suppression (>90%) of the Xe (6p6s) fluorescence is obtained for laser intensities of 50 MW cm-2. Measurements of the absolute electron density confirm that this effect is due to depletion of the dimer-ion concentration rather than photoionization of the 6p[12]0 state. However, photoionization of the Xe (6s or 6p) levels is observed and the cross section is measured to be 2.3×10-18 cm2 at 351 nm. These experiments demonstrate a means for studying the collisional kinetics of rare-gas dimer ions in real time and in the presence of large background gas pressures.