Non-adiabaticity in terms of dynamic potentials. An analysis of linear e⊗ϵ vibronic states

Abstract Non-adiabaticity of the linear E ⊗ϵ vibronic states is studied in terms of the difference between state-dependent non-adiabatic potentials and conventional adiabatic potentials. The former are obtained by constructing the non-adiabatic equation based on the conditional probability factorization of non-adiabatic states and formally similar to their adiabatic counterparts. We found that non-adiabaticity is mainly due to a kinetic energy contribution. Even in a region of strong non-adiabaticity (i.e. near the degenerate point), the nuclear radial motion is well separated from the nuclear azimuthal and the electronic motion. In the case of strong vibronic coupling, though the adiabatic potential gives a good approximation to the eigenvalues, our result shows that non-adiabaticity remains.