Oscillator strengths for transitions to Rydberg levels in 12C16O, 13C16O and 13C18O between 967 and 972 Å

Absorption oscillator strengths have been determined from high-resolution spectra in the 967-972 Angstrom region of three CO isotopomers for transitions to the Rydberg levels 4ppi(0), 3dpi(1) and 4psigma(0), as well as to the mixed E(6) level recently characterized by Eidelsberg et al. (2004). Synchrotron radiation from the Super-ACO electron storage ring at Orsay (LURE) was used as a light source. Oscillator strengths were extracted from the recorded spectra by least-squares fitting of the experimental profiles with synthetic spectra taking into account the homogeneous and heterogeneous interactions of the four levels. Column densities were derived from fits to the 3ppi(0) absorption band whose oscillator strength is well established. These are the first reported measurements for (CO)-C-13-O-18. For (CO)-C-12-O-16, our results are consistent with the larger values obtained in the most recent laboratory and astronomical studies.