Matrix elements of spin-adapted reduced Hamiltonians.

Abstract

General formulas for matrix elements of the pth-order spin-adapted reduced Hamiltonian (p-SRH) are derived based on the theory of generalized reduced density operators. The method is illustrated by a diagrammatic technique developed in detail for p=4. The p-SRH is a matrix representing a p-particle operator in a finite-dimensional p-particle Hilbert space. It is related to the N-particle (N\ensuremath{\ge}p) Hamiltonian defined in an N-particle spin-adapted, finite-dimensional Hilbert space. The p-SRH's, apart from their importance in theory of atomic and molecular structure, may find applications in statistical theories of spectra and in nuclear shell theory.