title: Precision measurement of the rotational energy-level structure of the three-electron molecule He2.
abstract: The term values of all rotational levels of the4He2+X+2Σu+(ν+=0) ground vibronic state with rotational quantum number N+≤ 19 have been determined with an accuracy of 8 × 10-4cm-1(∼25 MHz) by multichannel-quantum-defect-theory-assisted Rydberg spectroscopy of metastable He2∗. Comparison of these term values with term values recently calculated ab initio by Tung et al. [J. Chem. Phys. 136, 104309 (2012)] reveals discrepancies that rapidly increase with increasing rotational quantum number and reach values of 0.07 cm-1(∼2.1 GHz) at N+= 19.
authors.affiliation: Laboratory of Physical Chemistry, ETH Zurich, CH-8093 Zurich, Switzerland.
authors.forename: Luca
authors.initials: L
authors.lastname: Semeria
authors.affiliation: Laboratory of Physical Chemistry, ETH Zurich, CH-8093 Zurich, Switzerland.
authors.forename: Paul
authors.initials: P
authors.lastname: Jansen
authors.affiliation: Laboratory of Physical Chemistry, ETH Zurich, CH-8093 Zurich, Switzerland.
authors.forename: Frédéric
authors.initials: F
authors.lastname: Merkt