Dispersed fluorescence studies of linear LiOLi: a strongly bound, but very `floppyʹ ionic molecule

By dispersing laser-induced fluorescence (LIF) due to transitions from bent, excited LiOLi(1B1,K′=1) rovibrational states to linear ground-state LiOLi[X̃1Σg+(ν1″,ν2″,ν3″)] vibrational states, we have determined 37 (ν1″,ν2″,ν3″) vibrational eigenstate energies, each to an accuracy of about ±10 cm−1. An eight-term power series fit of the energies results in estimates of the ω1″, ω2″, ω3″ fundamental frequencies, the χ11″, χ22″ anharmonicity constants, and the χ12″, χ23″, χ13″ coupling constants. For such a strongly bound ionic molecule (Li1+O2−Li1+), LiOLi is remarkably floppy, with a `light-atomʹ ω2″ bending frequency of only 122±4 cm−1.