1. 1 The Red Rectangle Nebula excited by excited species Nadine Wehres, Claire Romanzin, Hans Van Winckel, Harold Linnartz, Xander Tielens

2. 2 The Red Rectangle Nebula excited by excited species Nadine Wehres, Claire Romanzin, Hans Van Winckel, Harold Linnartz, Xander Tielens identify molecules in space and laboratory  constraining physical and chemical conditions in RR

3. 3 identify molecules in space and laboratory  constraining physical and chemical conditions in RR

4. 4  The Red Rectangle proto-planetary nebula  The observations  The laboratory experiments  Simulations  Conclusion Outline

5. 5 The Red Rectangle Nebula Van Winckel et al., A&A, 2002, 390, 147 The post AGB star shows episodic mass loss that still enriches the surrounding nebula and is a great laboratory for ongoing molecule formation

6. 6 The optical emission features of the Red Rectangle Van Winckel et al., A&A, 2002, 390, 147 Extended Red Emission and molecular bands solid state species and gas phase molecules

7. 7 Molecules in the Red Rectangle  Small molecules have been identified: 12 CO; 13 CO; CO 2 ; OH; CH; CH + ; CN  Larger species have not been identified sofar, however  Typical PAH emission features are observed: 3.3; 6.2; 7.7; 8.6; and 11.3 µm  Silicate emission features

8. 8 New Technology Telescope, La Silla, Chile Obtain complete and medium resolution data-set of spectral progression with distance from central star

9. 9 Observations of the Red Rectangle emission features – Using the New Technology Telescope at La Silla, Chile Very faint object: long slit spectroscopy for better S/N Measurements performed for: Central Star 3 “; 6 “; 7 “; 11 “; 14 “; 16 “; and 20 “ Van Winckel et al., A&A, 2002, 390, 147

10. 10

11. 11 Laser Induced Fluorescence Spectroscopy Search for Carriers  Emission Spectroscopy vs. Absorption Spectroscopy Open Questions:  What is causing the observed features ?  Can we simulate the Red Rectangle in the laboratory?  Can we conclude on the actual physical conditions?

12. 12 Discharge Source: expanding acetylene (C 2 H 2 ) plasma - Carbon radicals - Transient species: Ions and radicals - Rovibronically excited species Nevertheless, rotationally cold species because of adiabatic expansion

13. 13 d 3 π g (v’=0) a 3 π u (v”1) d 3 π g (v’=1) a 3 π u (v”=2) C 2 Swan-Band transitions

14. 14 C2?C2?C2?C2? Peak Positions

15. 15 Simulations: Rotational contour fitting routines

16. 16 Simulations: Rotational contour fitting routines

17. 17 Simulations: Rotational contour fitting routines

18. 18 Conclusions Unambiguous identification of excited C 2 in the Red Rectangle at several distances in the outflows (at 3”, 6” and 7”) Corresponding with Swan band transitions d 3 π g – a 3 π u (v”,v’) = (1,0) and (2,1) Rotational contour simulations show a temperature of about 550 +/- 200 K in the nebula at closer distances

19. 19 Work in progress  CH + has been identified: T rot of ‘only’ 120 K ± 50 K (Hall et al. (1992), Nature, Vol 358)  Why is C 2 warmer – a chemical reason ?  statistical equilibrium equations (radiative transfer mechanism) of the excitation pathways of C 2  Formation and destruction scheme of C 2  Spectral dynamics of other observed bands as function of the distance to the central star.  … and as emission probe for absorption features:

20. 20 Sarre et al., Science 1995, 269, 674 DIBs Red Rectangle Seen in interstellar clouds towards reddened stars

21. 21 Thank you for your Attention