Isostationary functions for multimode and multilevel Jahn-Teller systems

The method of isostationary functions, first introduced for linear Jahn-Teller problems within a single electronic term, is generalized to multimode and multilevel problems. Analytic expressions are obtained for the case of linear vibronic coupling of a general form, including both simply and non-simply reducible groups. It is shown that the static multimode Jahn-Teller problem for non-simply reducible groups can always be reduced to an ideal single-mode problem.