Rf. Bishop et al., Simple approximations for the pseudo-Jahn-Teller Hamiltonian using the coupled cluster method, INT J MOD B, 15(10-11), 2001, pp. 1728-1731
The normal coupled cluster method has been used to obtain simple accurate a
p proximations to the ground and first excited state energies of the linear
e x E pseudo-Jahn-Teller Hamiltonian.