Quantum-Mechanical Selection Rules

David W. Ball

Guillermo Romero, P. Forn-Díaz, C. J. P. M. Harmans +2 more

Nigel B. Backhouse

The recognition of antiunitary symmetry in a quantum mechanical system is considered in relation to selection rules. It is shown that the interaction of unitary symmetry and the anti-invariance of matrix elements under antiunitary operators can produce extra selection rules in magnetic systems. The criteria obtained for the occurrence of these additional selection rules are presented in the form of group character tests, and in a special case provide an application for the symmetrized and antisymmetrized squares of group representations.

P. Schattschneider

Kenneth R. Brownstein, K. S. Capelle

The selection rule for matrix elements, <n j |αβ| n k >, of a product of operators, αβ, can be obtained by compounding the selection rules for the matrix elements <n j |α| n k > and <n s |β| n k > of the individual operators through intermediate states | n s . We point out that a naive application of this technique may lead to misleading results due to nonexistent intermediate "ghost" states.