Gerade Rydberg states of Xe2 probed by laser spectroscopy in the afterglow of a Xe microplasma: Ωg←a3Σu+(1u,Ou-) transitions in the near-infrared (675-800 nm)

Gerade Rydberg states of Xe2 lying 12 500-14 800 cm−1 above the a3Σu+(1u,Ou-) metastable levels of the dimer have been observed by laser spectroscopy in the afterglow of a Xe microplasma with a volume of ∼160 nL. Photoexcitation of Ωg←a3Σu+(1u,Ou-) (Rydberg ← Rydberg) state transitions at small internuclear separations (R≃Re(Xe2+)) while monitoring the suppression of Xe2(Ou+→Og+) spontaneous emission in the ultraviolet confirms the presence of an extensive series of red-degraded vibrational bands in the 675-800 nm region that are tentatively identified with an Ω = 1 upper state with a molecular ion core having predominantly B2Π3/2g character. Spectral simulations yield the following constants for the 1g state: Re′=3.49±0.1Å, Te = 12 980 ± 70 cm−1, ωe′=122±3 cm−1, ωe′xe′=0.9±0.2 cm−1, and De′=2250±70 cm−1.