Expressions are derived for the matrix elements of the transition operator relevant to that situation in which so-called surface potentials are to be taken into account as perturbations upon the usual core potentials. Some comparison is made of the class of approximations which appear in the literature and the restrictions upon their generality.

• Received 10 October 1957

DOI:https://doi.org/10.1103/PhysRev.109.2141