AAS 206th Meeting, 29 May - 2 June 2005
Session 32 Highlights in Laboratory Astrophysics
Poster, Wednesday, 10:00am-7:00pm, Thursday, 9:20am-2:00pm, June 1, 2005, Ballroom A

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[32.07] Oscillator Strengths for Rydberg Transitions in CO and Its Isotopomers

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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