Collision-induced absorption in the region of the O-2 fundamental: Bandshapes and dimeric features

The oxygen fundamental collision-induced absorption bandshapes are simulate d for temperatures between 90 and 296 K. It is shown that the use of line-m ixing formalism allows nice simulation of the observed bandshapes including minor regular ripples superimposed on the smooth continuum in the region o f the S and O branches. Weak absorption due to tightly bound oxygen dimers manifests itself as pseudodiatomic PR-like structure atop the monomer O bra nch. Consideration of the temperature variations of this structure allows t he oxygen-dimer effective rotational constant [B] to be roughly characteriz ed. The value of [B] is notably lower than the ground state value B-0 retri eved recently by high-resolution laser probe of oxygen dimers formed in a s upersonic slit expansion. This may be considered an indication of significa nt deviation of the (O-2)(2) structure averaged over the ensemble of therma lly excited dimers from that characterizing the ground state, (C) 2000 Acad emic Press.