A b i n i t i o study of the three lowest states X 2∑+, 2Π1/2, 2Π3/2, and B 2∑+ of the HeNe+ ion: Potential energy curves, Λ doubling, and predissociation rates of the rotational levels in the 2Π1/2 (v=0) state

Multireference configuration interaction calculations are performed for the X 2∑+, 2Π, and B 2∑+ states in HeNe+ from 2.2 to 100 bohr. The various perturbations of the Born–Oppenheimer states are evaluated: the spin–orbit interaction is calculated up to second order by employing the Breit–Pauli Hamiltonian. The resulting potential curves for the A 2Π1/2 state are compared with the experimental data of Dabrowski and Herzberg (Ref. 1), the curve of the hereto undetected A 2Π3/2 is predicted. The Λ splitting of the A1 2Π3/2 and the A2 2Π1/2 states due to coupling of the electronic motion with the rotation of the nuclear framework is computed by employing a basis of vibronic eigenfunctions. The calculated parameters of p0=−1.407 cm−1 for A2 2Π1/2 agree well with the corresponding data of p0=−1.417 or −1.427 cm−1 derived from measurements (Refs. 1 and 2). The predissociation rates of the rotational levels in the A2 2Π1/2 (v=0) state are also calculated on the basis of the computed ab initio data. All results are compared with the experimental data of Carrington (Ref. 2). The mechanism for the predissociation of the A 2Π1/2 state (in the absence of a curve crossing) is elucidated.