Evaporation of hot mesoscopic atomic metal clusters

Abstract

The evaporation times of hot mesoscopic sodium clusters are estimated using the microscopic and microcanonical statistical model of Weisskopf and the macroscopic canonical kinetic gas theory. The level density of liquid sodium clusters as function of the internal excitation energy is computed from the experimentally known thermodynamic quantities of the bulk matter. In using the known temperature dependent surface tension and standard thermodynamics, both theories are corrected to take into account finite size effects. By this method it is possible to obtain decay rates and internal level densities of mesoscopic clusters at excitations where any harmonic approximation breaks down. For clusters having more than about 200 atoms, the evaporation times obtained from the two models are practically equal.