Ground states of weakly boundthree-atom systems: energies and shapes of 4He2Xclusters from Monte Carlo calculations

Abstract

The interactions between alkali atoms and 4He, as well asthose between H- and 4He, are known to be even weaker thanthose between two helium atoms. In this work we show thatwhen the three-particle potential energy surface is obtained asa sum of two-body functions, the ensuing ground stateconfigurations are indeed very weakly bound and acquire spatialshapes difficult to describe in simple configurational terms. Wehave employed the quantum diffusion Monte Carlo method toanalyse the He2Li, He2Na and He2H-systems, for which possible molecular `shapes' are extractedfrom the final DMC distributions by defining within themconventional chemical structures with varying degree of`stiffness' attached to the nuclear positions.