Rovibrational computations for the He${}_2$ a ${}^3\hat{I}{\pounds }_{\mathrm{u}}^{+}$ state including non-adiabatic, relativistic, and QED corrections

Abstract

A potential energy curve (PEC) accurate to a fraction of 1 ppm ($1:10^6$) is computed for the ${}^3\hat{I}{\pounds }_{\mathrm{u}}^{+}$ state of He${}_2$ endowed with relativistic and QED corrections. The nuclear Schrödinger equation is solved on this PEC with diagonal Born-Oppenheimer and non-adiabatic mass corrections to obtain highly accurate rotational-vibrational levels. The computed rovibrational intervals and fine-structure splittings, spanning over several orders of magnitude in energy, are found to be in remarkable agreement with available high-resolution spectroscopy data.