Abstract:
Very accurate quantum mechanical calculations of the pure vibrational spectrum of the HeH molecular
ion are reported and compared with newly obtained pure vibrational transitions extracted from the
available experimental data. The calculations are performed without assuming the Born-Oppenheimer
approximation regarding separability of the nuclear and electronic motions and include the first order
relativistic mass-velocity and Darwin corrections. For the two lowest transitions, whose experimental
energies are established with the highest precision, the calculated and the experimental results show very
good agreement