Oscillator Strengths and Predissociation Rates for W – X Bands and the 4p5p Complex in 13 C 18 O M. Eidelsberg, J.L. Lemaire (Obs. de Paris), S.R. Federman (U. of Toledo), G. Stark (Wellesley), A.N. Heays (Leiden), L. Gavilan (Obs. de Paris), J.R. Lyons (ASU), P.L. Smith (Retired), N. de Oliveira, and D. Joyeux (SOLEIL) This research was supported by grants from NASA and CNRS-PCMI program

Outline Background New Results from SOLEIL Concluding Remarks

Background 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

Background Results on Diffuse Molecular Clouds (Sheffer et al. 2008, ApJ, 687, 1075) Selective Isotope Photodissociation 13 CO also self shielded Isotope Charge Exchange

Background Importance of Self Shielding (Sheffer et al. 2008)

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 750,000 (here we used 350,000) –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

SOLEIL Experiments Need calibration band: use B – X (0,0) –This band is isolated –For 12 C 16 O, its band f-value is well characterized (with weighted uncertainty of 6%) –For 13 C 18 O, close-coupling model of interaction between B 1 Σ + and D′ 1 Σ + indicates f-value varies less than 1.7% among isotoplogues (Stark et al. 2014, ApJ, 788, 67) Fit of 12 C 16 O band (Eidelsberg et al. 2012, A&A, 543, 69)

SOLEIL Experiments Our Previous Related Work Using SOLEIL Eidelsberg et al. 2012, A&A, 543, A69 – W–X bands and 4p5p complex in 12 C 16 O Eidelsberg et al. 2014, A&A, 566, A96 – W–X bands and 4p5p complex in 13 C 16 O and 12 C 18 O Heays et al. 2014, JCP, 141, – found new electronic state from analysis of perturbations involving W(1) band in all isotopologues Lefebvre-Brion & Eidelsberg 2012, J. Mol. Spec, 271, 59 Eidelsberg et al. 1991, A&AS, 90, 231 Eidelsberg et al. 2006, ApJ, 647, 1543

SOLEIL Experiments W – X bands W(0) R, P Q

SOLEIL Experiments –f-values consistent with earlier determinations, regardless of spectral resolution, because predissociation rates large –Agreement found with earlier predissociation rates, but now see J- dependence –For (2,0) band, perturbation likely present (line by line best fit with polynomial, as seen in 13 C 16 O and 12 C 18 O) –For (0,0) band, see differences for e- and f-parity levels W(0)

SOLEIL Experiments Isotopologue/Bandf-value (  10 3 ) Predissociation Rates (10 11 s -1 ) e parityf parity 12 C 16 O (0,0)14.3(1.1)0.09(0.02)+0.019(.001)x0.10(0.01) (0.0001)x 13 C 16 O12.67(0.82)0.220(0.060)+0.011(0.001)x0.187(0.009)+0.002(0.001)x 12 C 18 O13.94(0.86)0.226(0.021) (0.0004)x0.228(0.009) ( )x 13 C 18 O11.6(0.8) 0.320(0.026) (0.0008)x0.266(0.021) (0.0003)x 12 C 16 O (2,0)28.9(2.1) 1.12(0.05)+0.010(0.001)x0.75(0.04) (0.0002)x 13 C 16 O27.14(1.72)0.472(0.043) (0.0011)x +[9.4(0.6)]10 -5 x (0.043) (0.0011)x +[9.4(0.6)]10 -5 x 2 12 C 18 O26.40(1.63)0.644(0.004) ( )x +[5.27(0.35)]10 -5 x (0.004) ( )x +[5.27(0.35)]10 -5 x 2 13 C 18 O22.87(1.85) 0.733(0.053) (0.0023)x +[9.0(1.0)]10 -5 x (0.053) (0.0023)x +[9.0(1.0)]10 -5 x 2 12 C 16 O (3,0)19.2(1.4) 2.07(0.10)+0.046(0.002)x1.80(0.09)+0.048(0.002)x 13 C 16 O15.92(1.02)1.998(0.064) (0.0028)x1.680(0.021) (0.0004)x 12 C 18 O18.10(1.12)1.70(0.06)+0.164(0.004)x1.41(0.02) (0.0002)x 13 C 18 O13.79(1.08)3.43(0.26)+0.173(0.021)x3.41(0.34)

SOLEIL Experiments Results for 4p5p Rydberg Complex –For the most part, f-values and predissociation rates are only determinations –4pπ(2), 5pπ(0), and 5pσ(0) much more blended in 13 C 18 O compared to other isotopologues

SOLEIL Experiments

–Another band appears within P branch of 5pσ(0) band, probably the 4pσ(2) band – See continuum feature like that seen in 12 C 16 O Wavelength (Å) Intensity

Concluding Remarks VUV FTS allows us to extract data on individual bands, including predissociation rates that vary with J The complexities – indications of perturbations, presence of continuum features, and heavy blending – require guidance from theoretical models Next steps: –Analyze perturbations in B–X series of bands –Obtain f-values for A–X and triplet-singlet bands in 13 C 16 O –Obtain f-values for bands involving the B, C, and E states with greater precision (<5%) for photochemical models