The bound and quasibound levels of 6Li2 a 3Σ+u

Abstract
Rotationally resolved 6Li2 2 3Π g →a 3Σ+ u fluorescence spectra have been obtained by perturbation facilitated optical–optical double resonance spectroscopy. Principal molecular constants for the a 3Σ+ u first excited state of 6Li2 are (2σ uncertainties): T e =8180.9±5.4 cm− 1, ω e =73.0±1.4 cm− 1, ω e x e =3.95±0.14 cm− 1, R e =4.13±0.08 Å, and D e =336.0±5.4 cm− 1. Transitions into 0≤v≤6 and N=18, 20, 31, 33 were observed and the total number of bound rotation–vibration levels was computed to be 193 for the a 3Σ+ u state of 6Li2.