Non-adiabatic mass-correction functions and rovibrational states of 4He2+ (X 2Σu+)

The mass-correction functions in the second-order non-adiabatic Hamiltonian are computed for the He-4(2)+ molecular ion using the variational method, floating explicitly correlated Gaussian functions, and a general coordinate-transformation formalism. When non-adiabatic rovibrational energy levels are computed using these (coordinate-dependent) mass-correction functions and a highly accurate potential energy and diagonal Born-Oppenheimer correction curve, significantly improved theoretical results are obtained for the nine rotational and two rovibrational intervals known from high-resolution spectroscopy experiments. Published by AIP Publishing.