EVAPORATION OF HOT MESOSCOPIC ATOMIC METAL-CLUSTERS

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