EVAPORATION AND CONDENSATION OF CLUSTERS

Influence of surrounding matter on the properties of clusters is consi dered by an approach combining the methods of statistical and quantum mechanics. A cluster is treated as a bound N-particle system and surro unding matter as thermostat. It is shown that, despite arbitrary stron g interactions between particles, cluster energy can be calculated by using the controlled perturbation theory. The accuracy of the latter i s found to be much higher than that of the quasiclassical approximatio n. Spectral distribution is obtained by minimizing conditional entropy . Increasing the thermostat temperature leads to the depletion of boun d states. The characteristic temperature when bound states become esse ntially depleated defines the temperature of cluster evaporation. The inverse process of lowering the thermostate temperature, yielding the filling of bound states, corresponds to cluster condensation.