Photodissociation of Kr+<i>n</i> clusters

Abstract

The photodissociation of Kr+n (3≤n≤11) cluster ions is observed for the first time in the 565 to 630 nm wavelength range. Kr+3 has a photodissociation cross section of (8.1±0.8)×10−17 cm2 at 612 nm, while Kr+4 and Kr+5 are found to have larger photodissociation cross sections than Kr+3 with a slightly red-shifted spectrum. Only Kr+ is detected as a photofragment of Kr+3, while in the Kr+n (4≤n≤7) experiments, both Kr+2 and Kr+ photofragments are seen. As size n increases from 7 to 11, Kr+ disappears and Kr+3 appears. Laser power studies show that all are single photon photodissociation processes. For higher order Kr+n clusters (4≤n≤7) the intensity ratio between the two photodissociation products Kr+2 and Kr+ is dependent on the wavelength of the laser light used in the photodissociation, but independent of the polarization direction of the laser. Translational energy analysis of the photofragments is used to investigate the photodissociation mechanisms. In contrast to the photodissociation of Kr+3, where two types of Kr+ photofragments with different values of translational energy release are observed, only one type of Kr+2 photofragment, with zero kinetic energy release is found in the Kr+4 photodissociation. These findings are discussed in terms of the dynamics of photodissociation and possible structures of these cluster ions.