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Y. Sheffer, S. R. Federman (U. Toledo), M. Eidelsberg, J. L. Lemaire, J. H. Fillion, F. Rostas (Obs. Paris Meudon and U. Cergy-Pontoise), J. Ruiz (U. Malaga)
Precise knowledge of CO oscillator strengths (f-values) is an important ingredient in modeling this molecule's interstellar distribution, owing to line absorption that dominates CO's photodissociation. High-resolution (R = 25-60,000) FUV absorption spectroscopy from the Super-ACO synchrotron at Orsay, France, is employed to measure new f-values for three CO isotopomers: 12C16O, 13C16O, and 13C18O. We use the f-value of the E-X (0-0) band at 1076~Å\ as the calibrator of CO column density. A cluster of four interacting Rydberg states between 968-970~Å, K-X (0-0)~+ L-X (0-0)~+ L\prime-X (1-0)~+ E-X (6-0), is successfully disentangled and modeled by taking into account state interactions according to their mixing coefficients. The derived f-values agree with the larger values found in previous lab work, and with values derived from our FUSE interstellar spectra. Other Rydberg bands are being analysed, including W-X (v\prime-0; v\prime~=~0~to~3) between 925 and 972~Å, E-X (1-0) at 1051~Å, and B-X (6-0) at 1002~Å, with the last showing marked predissociation lifetime variations from one isotopomer to another. Final f-values will be compared with available results. The authors acknowledge the support of the LURE-SuperACO synchrotron facility through time allocation and the SU5 beam-line team. This work was funded in part by NASA and the CNRS-PCMI program.
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Bulletin of the American Astronomical Society, 37 #2
© 2005. The American Astronomical Soceity.