Non-adiabatic, Relativistic, and Leading-order QED Corrections for Rovibrational Intervals of $^4$He$_2^+$ ($X\ ^2\Sigma_\mathrm{u}^+$)

Abstract

The rovibrational intervals of the $^4$He$_2^+$ molecular ion in its $X\ ^2\Sigma_\text{u}^+$ ground electronic state are computed by including the non-adiabatic, relativistic, and leading-order quantum-electrodynamics corrections. Good agreement of theory and experiment is observed for the rotational excitation series of the vibrational ground state and the fundamental vibration. The lowest-energy rotational interval is computed to be $70.937\ 69(10)$ cm$^{-1}$ in agreement with the most recently reported experimental value, $70.937\ 589(23)(60)_\text{sys}$ cm$^{-1}$ [L. Semeria, P. Jansen, G.-M. Camenisch, F. Mellini, H. Schmutz, and F. Merkt, Phys. Rev. Lett. 124, 213001 (2020)].