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

Abstract

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 (X3Σ0+,1-,a1Δ2, b1Σ0++ and A3Π0-,0+,1,2) of NH molecule are obtained by the multi-reference configuration interaction (MRCI) plus Davidson correction. The spectroscopic constants (Re, ωe, ωeχe, Be, De) 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 X3Σ0+-↔A3Π1, X3Σ1-↔A3Π0+ and X3Σ1-↔A3Π0- transitions are considered. The feasible laser cooling schemes using a single laser are formulated. In the proposed cooling scheme, there wavelengths for the X3Σ0+-↔A3Π1 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.