Evaporation of clusters in a heat bath

A new experimental method, where sodium clusters are passed through a gas-filled thermostat before they are cooled and subjected to time-of-flight mass analysis, is presented. Decay rates, κ(N), and activation energies, D(N), for evaporation from the least-bound clusters are determined with good accuracy. The cluster distributions emerging from the heat bath are more strongly modulated by shell effects than previously observed with ensembles of clusters evaporating in vacuum.