- The HerndonSimpson model for a particular catacondensed polyphene chain is considered as a nontrivial manybody Hamiltonian, defined on a space with a basis of orthonormal Kekul structures. An Explicitly correlated cluster expanded resonancetheoretic wave function is described for this model, and its quality is judged by calculation of the standard deviation for the energy expectation. The quality is found to be high. Indeed, for a particular parameter ratio within the range of experimental interest, the wave function ansatz is found to be exact. This very accurate solution is then used to gauge the quality of the common ansatz with equally weighted Kekul structures, and it is found to be reasonably good. Copyright 1989 John Wiley & Sons, Inc.