Long range binding in alkali-helium pairs

Variational calculations are pet-formed to search for bound rovibrational states of diatomic molecules formed from alkali atoms and helium in the very shallow (2)Sigma electronic ground state. Examination of a recent set of potential surfaces and several older potentials indicates that all pairs possess a single very diffuse bound state with J = 0. Such marginally bound states will have profound effects on low energy collisions between alkali atoms and helium atoms. The sensitivity of these states with respect to retardation effects has been studied. The variational calculations employ a basis set of generalized Laguerre functions and new analytical expressions for kinetic energy matrix elements.