Transition dipole moments, transition probabilities, and radiative lifetimes for NH by ab initio effective valence shell Hamiltonian

The effect of spin-orbit coupling on molecular properties: Potential energy curve, transition dipole moment and laser cooling scheme of NH

The influence of spin-orbit coupling on the cooling of NH molecular laser is investigated based on the ab initio theory. The potential energy curves (PECs) and spectral constants for four Λ-S states (X³Σ^-, a¹Δ, b¹Σ⁺ and A³Π) and eight Ω states [Formula: see text] a¹Δ₂, [Formula: see text] and [Formula: see text] ) of NH molecule are obtained by the multi-reference configuration interaction (MRCI) plus Davidson correction. The spectroscopic constants (R_e, ω_e, ω_eχ_e, B_e, D_e) are obtained by solving the one dimensional radial Schrödinger equation, and the results are almost the same as the previously reported data. In addition, the transition dipole moment, permanent dipole moment, Franck-Condon factors, and radiative lifetime of NH molecule are also acquired. Also, the effects of the intermediate state on the [Formula: see text] , [Formula: see text] and [Formula: see text] transitions are considered. The feasible laser cooling schemes using a single laser are formulated. In the proposed cooling scheme, there wavelengths for the [Formula: see text] are used, the main pump lasers are λ₀₀ = 335.74 nm. The feasible transition is based on this. It is found that spin-orbit coupling has a significant effect on potential energy curves, permanent dipole moments, transition dipole moments and vibration energy levels.

The effective valence shell Hamiltonian calculations of spin-orbit splittings in small diatomic hydrides

Recently, the size extensive, ab initio effective valence shell Hamiltonian method for spin-orbit coupling has been suggested. In essence, this effective Hamiltonian method is equivalent to the quasidegenerate perturbation theory. But the difference lies in transforming the original Hamiltonian into an effective Hamiltonian acting within a relatively small valence in the effective valence shell Hamiltonian method. One advantage of the method is that the spin-orbit coupling energies of all valence states for both the neutral species and its ions are simultaneously determined with a similar accuracy from a single computation of the effective spin-orbit coupling operator. Thus, fine structure splittings are predicted for a number of states of each system for which neither experiment nor theory is available. To assess the accuracy of the effective Hamiltonian method more extensively, test calculations are performed for the spin-orbit splittings in the valence states of small diatomic hydrides and their ions. The calculated spin-orbit splittings are generally in good agreement with experiments and with other ab initio computations.