Precision measurement of the rotational energy-level structure of the three-electron molecule He${}_2^{+}$

Luca Semeria, Paul Jansen, Frédéric Merkt

The term values of all rotational levels of the ${}^4$He${{}_2}^{+}{X}^{+}{}^2{\Sigma }_u^{+}({\nu }^{+}=0)$ ground vibronic state with rotational quantum number $N^{+}\le 19$ have been determined with an…