(C) 1994 Harwood Academic Publishers GmbH Printed in Malaysia PHOTODISSOCIATION DYNAMICS OF Arn/ CLUSTER IONS

The time-of-flight (TOF) spectra of Ar and Ar fragments produced in the photodissociation of Am+ (3-< _ n--< _ 24) were measured at wavelength around 540 nm. The kinetic-energy and angular distributions of the neutral photofragments were obtained for n 3, 9 and 24 by a simulation analysis of the measured TOF spectral profiles. The overall aspect of the photodissociation process of Ar is deduced from these distributions within the context of trimer ion core model; a linear Am core is solvated by neutral Ar atoms. For Am+n with 4 _<- n < 14, direct dissociation of the A chromophoric core gives rise to Ar and/or Ar fragments with a high kinetic energy release. For the larger Am+ (n 14), the production of high-kinetic-energy fragments is suppressed; "evaporation " of the solvent Ar atoms is instead the dominant channel of photofragmentation. KEY WORDS: photofragment kinetic-energy and angular distributions 1