1. HD 204827, the C 2, C 3 rich sightline

2. The C 2 Diffuse Interstellar Bands Takeshi Oka Department of Astronomy and Astrophysics And Department of Chemistry The Enrico Fermi Institute, University of Chicago J. A. Thorburn, L. M. Hobbs, T. Oka, D. E. Welty, D. G. York B. J. McCall, S. D. Friedman, P. Sonnentrucker, T. P. Snow ApJ 584, 339-356 (2003) Carbon in space, Lago di Como, May 23, 2006 T. Oka, Thorburn, J. A., McCall, B. J., S. D. Friedman, L. M. Hobbs, P.Sonnentrucker, D. E. Welty, D. G. York ApJ 582, 823-829 (2003)

3. HD 204827, the C 2, C 3 rich sightline

4. William Huggins, Comet Tebbutt, 1881 1942 1951 Alex Douglas C 3 1966 IVR The Douglas effect 1975 HCCCCCN, 1977-8 HCCCCCCCN, HCCCCCCCCCN Origin of diffuse interstellar lines Nature, 269 130 (1977) Alex Douglas CnCn Proc. R. Soc. London, A. 34, 148 (1881) 4050 Å

5. J. A. Thorburn, L. M. Hobbs, T. Oka, D. E. Welty, D. G. York, B. J. McCall, S. D. Friedman, P. Sonnentrucker, T. P. Snow Apache Point Observatory 3.5-meter 3,800–10,000 Å ; /  ~ 38,000 (8 km/s) 53 stars, 0.11 800 at 5780 Å Systematic observations of DIBs

6. HD 183143 versus HD 204827 E(B-V)= 1.27 1.11 C 2 C 3 N(C 2 ) < 6  10 12 cm -2 = 440  10 12 cm -2 High discrimination N(CH) = 50  10 12 cm -2 = 80  10 12 cm -2 Poor discrimination C 2 richC 2 poor

7. C 2 rich C 2 poor C 2 DIBs Minority Weak and sharp Diffuse Interstellar Bands

8. W(DIB) versus N(C 2 ) 4984.82 Å r = 0.857 5418.92 Å r = 0.905 C 2 DIBsNon-C 2 DIBs 5780.59 Å r = 0.305 6397.39 Å r = 0.416

9. C 2 DIBs λ(Å)Δλ(Å)r(C 2 )r(C 3 )Note 4363.810.500.6230.559 4734.770.390.7970.795 4963.880.730.7570.668 4969.140.790.8560.640 4979.610.470.7620.734 4984.790.500.8570.593 5170.570.440.6340.413 5176.040.690.8430.687 5418.870.850.9050.693 5512.680.570.6840.431 5541.870.450.7420.576 5546.480.530.8020.787 5762.760.48 5769.160.490.7490.565 5793.220.71 6729.250.440.782 21.3 cm -1 20.9 cm -1 20.4cm -1 15.0 cm -1 19.1 cm -1

10. Doublet Lines

11. The Doublets 4963.99 4969.24 4979.64 4984.82 5170.57 5176.04 5541.87 5546.48 5762.76 5769.16 21.3 cm -1 20.9 cm -1 20.4 cm -1 15.0 cm -1 19.1 cm -1 Π Π Π Σ HC 3 HC 5 HC 6 HC 7 HC 8 C 3 - C 7 - A (cm -1 ) 14.4 23.7 -15.1 26.2 -19.3 26.6 27.4 λ (Å) Δ 4.0 3.8 2.4 1.8 2.2 3.1 2.8 1.6 1.0 1.1 1.0 1.5 2.0 1.3 T ex 22 K 34 K 26 K Π←Σ 3  10 6 s I s / I w A HD 204827 HD 147889 HD 172028 Or inverted

12. C 2 -rich HD 204827 Hot HD 34078 T = 301 K T = 40.6 K

13. C 2 rich C 2 poor C 2 DIBs Minority Weak ans sharp

14. Keck Adamkovics, Blake and McCall B = 365 MHz for T = 100 K 182 MHz 200 K 122 MHx 300 K B = 564.00 MHz HC 7 N 290.52 MHz HC 9 N 169.06 MHz HC 11 N 2.60 cm -1

15. Summary DIBs which correlate well with C 2 and C 3 C 2 DIB HD 204827, Minority, Weak and sharp Doublet structure suggests spin-orbit splitting Linear carbon chain molecule Relatively high density ? DIBs for high temperature medium HD 34078 Rotational structure  B n  8 – 12? Big question: C 2, C 3  C 2 DIB or C 2 DIB  C 2, C 3 ?

16. HD 34078 T = 301 K HD 204827 T = 40.6 K C3C3 Adamkovics, Blake, McCall RA 06 The high temperature sightline HD 34078 R head