Rotationally resolved absorption spectrum of the O2 dimer in the visible range

The rotationally resolved absorption spectrum of two bands of the oxygen dimer near 630 and 578 nm have been recorded by intracavity laser absorption spectroscopy both in a supersonic slit expansion of pure O2 and in a cell cooled at 77 K. These bands correspond to the transitions [O2(1Δg)v=0]2←[O2(3Σg−)v=0]2 and [O2(1Δg)v=0–O2(1Δg)v=1]←[O2(3Σg−)v=0]2 . From the extension of the highly congested rotational structure, the dissociation energy of the ground and excited states are estimated to be 80 and 40 cm−1, respectively. These values agree reasonably well with the results of ab initio calculations of the potential energy surface.