Subthermal kinetic energy distributions of neutral atoms photodesorbed from Na cluster surfaces

Abstract

Two-photon laser techniques are employed to obtain high-resolution kinetic energy distributions of Na atoms which desorb from large, surface-bound Na clusters upon pulsed laser-excitation of surface plasmons. The measured translational energy distribution of the atoms is clearly non-Maxwellian with a cos 2θ angular dependence and most probable kinetic energies below that expected of atoms desorbing from a surface at thermal equilibrium. The experimental data is interpreted by a model which takes energy transfer between the desorbing Na atoms and the vibrating Na cluster surface into account.