Revised Term Values for the A – X (v′=0-9, v′′=0) Bands in 13 C 16 O from High- Resolution Spectra Acquired at the SOLEIL Synchrotron L. Gavilan, J.L. Lemaire, M. Eidelsberg, (Obs. de Paris), S.R. Federman (U. of Toledo), G. Stark (Wellesley), A.N. Heays (Wellesley/Leiden), J.-H. Fillion (UMPC), J.R. Lyons (UCLA), and N. de Oliveira (SOLEIL) This research was supported by grants from NASA and CNRS-PCMI program

Outline Background CO Photochemistry Results from SOLEIL Summary

Background CO observed in many astronomical environments –Diffuse and dark, molecular interstellar clouds –Circumstellar shells of asymptotic giant branch stars and planetary nebulae –Circumstellar disks around newly formed stars –Comets and planetary atmospheres Experimental data for photochemical models –Electronic transitions (ultraviolet) –Oscillator strengths –Predissociation rates

Photochemistry of Interstellar CO Processes affecting mix of isotopologues Isotope Charge Exchange – favors 13 C 16 O –It has lower zero-point energy – 13 C C 16 O → 12 C C 16 O – ΔE (ΔE/k ≈ 35 K) Selective Isotopic Photodissociation – favors more abundant isotopic variant –Dissociation occurs through line absorption at far UV wavelengths –More abundant variant has lines that are more optically thick, shielding itself from further dissociation

Photochemistry of Interstellar CO Accurate column densities needed –A – X (4 th positive) system of (ν′,0) bands in 12 C 16 O now have well-determined (self-consistent) f-values via electron scattering (Chan et al. 1993), laser absorption (Stark et al. 1998), and synchrotron absorption (Eidelsberg et al. 1999) –Agreement between astronomical f-values (e.g., Sheffer et al. 2002) and theoretical values (Eidelsberg & Rostas 2003) for triplet-singlet transitions (a′ – X, d – X, and e – X) is now excellent for 12 C 16 O, better than 1 σ in most instances Do the same values apply to 13 C 16 O?

SOLEIL Experiments DESIRS beamline with a VUV FTS at SOLEIL Synchrotron

SOLEIL Experiments The FTS (de Oliveira et al. 2009, Rev. Sci. Instru., 80, ; de Oliveira et al. 2011, Nature Photonics, 5, 149) –Resolving power as high as 1,000,000 –Based on wave front division instead of amplitude division –Relies on modified bimirror configuration requiring only flat mirrors –Path difference scanning through translation of one reflector

Results from SOLEIL

+ Predicted by Hakalla et al at J′ = ±1 * Previously seen in Kępa et al ** Previously seen in Kępa et al. 2011

Summary SOLEIL FTS extends VUV measurements to higher J′ for most bands and lower J′ for v′ = 0 Confirm previously assigned perturbations, but now seen in greater detail Evidence for new perturbations seen Next steps –Extract f-values for A – X bands in 13 C 16 O –Extract f-values for triplet-singlet bands for comparison with results for 12 C 16 O (Eidelsberg and Rostas 2003)

A New Division within the AAS The Laboratory Astrophysics Division: Brings users and providers together