Theoretical electronic structure of the lowest-lying states of the YI molecule

CAS-SCF/MRCI calculations have been performed for 15 molecular states in the representation 2S+1Λ(+/−) (neglecting spin-orbit effects) for the molecule YI. The corresponding 33 molecular states in the representation Ω(+/−) (including spin-orbit effects) have been calculated using a semi-empirical spin-orbit pseudopotential built up for yttrium. Calculated potential energy curves and spectroscopic constants are reported, to the best of our knowledge they are the first ones from ab initio methods for this molecule. Present results are compared to experimental accurate data available for the ground X1Σ+ and 3 excited states (1)1Π, (2)1Σ+ and (2)1Π.