Photodissociation Dynamics of Arn+ Cluster Ions
The time-of-flight (TOF) spectra of Ar+ and Ar fragments produced in the photodissociation of Arn+ (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 Arn+ is deduced from these distributions within the context of trimer ion core model; a linear Ar3+ core is solvated by neutral Ar atoms. For Arn+ with 4 ≦ n ≲ 14, direct dissociation of the Ar3+ chromophoric core gives rise to Ar+ and/or Ar fragments with a high kinetic energy release. For the larger Arn+ (n ≳ 14), the production of high-kinetic-energy fragments is suppressed; “evaporation” of the solvent Ar atoms is instead the dominant channel of photofragmentation.
