Physical Review A
Expansion of the spin-spin interaction
Keh‐Ning Huang
Abstract
The space part of a general spin-spin interaction is expanded in a complete orthonormal set of irreducible tensors constructed from spherical harmonics of the interacting particles. With this expansions, the $m$-scheme matrix element of the spin-spin interaction is represented as a sum of weighted radial integrals along with its graphical representation. The graphical form of the $m$-scheme matrix element enables one to obtain graphically matrix elements between many-particle configurations in any coupling scheme.