Rovibrational spectra of diatomic molecules in strong electric fields: The adiabatic regime

We investigate the effects of a strong electric field on the rovibrational spectra of diatomic heteronuclear molecules in a ${}^1{\Sigma }^{+}$ electronic ground state. Using a hybrid computational technique combining discretization and basis set methods, the full rovibrational equation of motion is solved. As a specific example, the rovibrational spectrum and properties of the carbon monoxide molecule are analyzed for experimentally accessible field strengths. Results for energy levels, expectation values, and rovibrational spectral transitions are presented. They indicate that, while low-lying states are not significantly affected by the field, for highly excited states strong orientation and hybridization are achieved. We propose an effective rotor Hamiltonian, including the main properties of each vibrational state, to describe the influence of an electric field on the rovibrational spectra of a molecular system with a small coupling between its rotational and vibrational motions. The validity of this approach is illustrated by comparison with the results obtained with the fully coupled rovibrational Schrödinger equation. We thereby demonstrate that it is possible to create state-dependent hybridization of a molecular system, which is of importance for vibrational state-selective chemical reactions. This state dependence is individually different for each molecular system and represents therefore a characteristic feature of the species.