CORRELATED-STATE EVALUATION OF THE 2ND VIRIAL-COEFFICIENT

The difference R(z) between the resolvents of the interacting and free Hamiltonians is inherently associated with (pair) particle correlatio ns and can also be used for the evaluation of the second virial coeffi cient. This paper explores the operator properties of R(z) and the ana lytical continuation of its momentum matrix elements. Correlated-state wave functions are identified when making a pole expansion of the ana lytically continued matrix elements. These square-integrable wave func tions have a one-to-one correspondence with resolvent poles, and as su ch are associated with resonance-bound-, and virtual-state momenta. Th eir properties and use in evaluating the second virial coefficient are discussed. Except for the bound states, these wave functions are not eigenvectors of the interacting Hamiltonian. The separable Yamaguchi p otential is used to illustrate these properties.