Ritz variational treatment of the 4He trimer

The He-4 trimer is treated by the Ritz variational method using trial functions whose accuracy has been tested by a similar treatment of the dimer, for which an exact solution exists. These are nodeless functions containing four nonlinear parameters that are varied to give the minimum value for the ground-state energy. Agreement with measurement is obtained for the mean bond lengths of the trimer, but there is some disagreement with other non-variational calculations of the ground-state binding energy. Copyright (C) EPLA, 2009