Photofragment Imaging of Kr2 and ArKr van der Waals Molecules following Two-Photon Excitation

Abstract

Photofragment imaging is used to study the fragmentation and ionization dynamics of Kr{sub 2} and ArKr upon absorption of two or more photons ({lambda} 211-220 nm). For Kr{sub 2} two-photon-excited electronic states are studied that are in energy near Kr (5p) states. All studied Kr{sub 2} two-photon-excited electronic states show competition between ionization and predissociation. The photofragment images also reveal higher order absorption processes in which three-photon absorption of the dimer is followed by dissociation into ground state and excited state Kr fragments. Dissociation after three-photon absorption leads to Kr photofragments. The Ar photofragment ion images and the multiphoton ionization spectra show competition between ionization and predissociation of these two-photon-excited ArKr states. As with the Kr{sub 2} dimer, the ion images also reveal higher order absorption processes in which three-photon absorption of ArKr is followed by dissociation into neutral Kr ground and Ar excited state fragments. The angular distributions of the fragments formed after predissociation at the two-photon resonant levels and after three-photon absorption are both anisotropic. Markedly different contributions of three-photon absorption and predissociation processes are observed in the ion images of the two electronic bands of ArKr. 52 refs., 10 figs., 5 tabs.