Statistical evaporation of rotating clusters. II. Angular momentum distribution

TL;DR

This paper investigates how atomic clusters change their angular momentum during evaporation, revealing effects like rotational cooling and heating through phase space theory and molecular dynamics, especially in Lennard-Jones clusters.

Contribution

It provides a detailed analysis of angular momentum distribution changes during evaporation, incorporating effects of potential shape, anharmonicity, and excitation energy, with validated theoretical predictions.

Findings

Lennard-Jones clusters show rotational cooling when thermally excited.

Strong vibrational excitation leads to rotational heating.

Phase space theory predictions align with molecular dynamics simulations.

Abstract

The change in the angular momentum of an atomic cluster following evaporation is investigated using rigorous phase space theory and molecular dynamics simulations, with an aim at the possible rotational cooling and heating effects. Influences of the shape of the interaction potential, anharmonicity of the vibrational density of states (DOS), and the initial distribution of excitation energies are systematically studied on the example of the Lennard-Jones cluster LJ_14. For this system, the predictions of PST are in quantitative agreement with the results of the simulations, provided that the correct forms for the vibrational density of states and the interaction potential are used. The harmonic approximation to the DOS is used to obtain explicit forms for the angular momentum distribution in larger clusters. These are seen to undergo preferential cooling when thermally excited, and preferential heating when subject to a strong vibrational excitation.