Ab initio calculations of the ground and excited states of the YN molecule including spin-orbit effects

摘要

The electronic structure with spin-orbit effects of the yttrium nitride YN molecule are investigated by the methods of multireference single and double configuration interaction, including Davidson correction to account for quadruple excitations (MRSDCI + Q). Spin-orbit effects are taken into account via a semiempirical pseudo-potential for the yttrium atom, while they have been neglected for nitrogen. The potential energy curves are calculated along with the spectroscopic constants for the lowest lying 38 spin-orbit states Ω in YN. A good agreement is displayed by comparing the calculated spectroscopic constants with those available experimentally. The permanent dipole moments are calculated along with the vibrational energies. We identify two vibrational energy levels in the spectra of the yttrium nitride molecule X~1Σ~+ (v = 0) → (1)~1Σ~+ (v' = 0) that satisfy the criteria of laser cooling in molecules. New results are obtained in the present work for 32 spin orbit states and their spectroscopic constants calculated.