Chemical Physics 530 (2020) 110637

Thermal damping of odd-even effects in gold clusters

K. Hansen^a,b,⁎

a Center for Joint Quantum Studies and Department of Physics, Tianjin University, 92 Weijin Road, Tianjin 300072, China

b Dept. of Physics, Gothenburg University, 41296 Gothenburg, Sweden

Abstract

The amplitude of the odd-even variation in binding energy is calculated for cationic gold clusters,Au_n⁺,n=8-26, extracted from experimental literature data. The data are found to agree fairly well with a simple Fermi gas estimate. Motivated by this, the canonical ensemble free energies are calculated for a ladder spectrum. Experimentally observed differences in ground state dissociation free energies between species with odd and even numbers of valence electrons reach the high temperature limit at temperatures significantly below values corresponding to the HOMO-LUMO gap. Remarkably, the asymptotic high temperature limit does not correspond to the complete disappearance of the zero temperature free energy difference. Likewise, the amount of electronically excited states are significantly higher than a simple estimate based on the Boltzmann factor of the gap energy, having implications for threshold ionization yields.