1. Fourier Transform Emission Spectroscopy of the B 2 Σ + -X 2 Σ + (Violet) System of CN R.S. Ram Department of Chemistry, University of Arizona, Tucson, AZ 85721 S. P. Davis, L. Wallace National Optical Astronomy Observatory, Tucson, AZ 85726 R. Engleman Department of Chemistry, University of New Mexico, Albuquerque, NM 87131 D. R. T. Appadoo Canadian Light Source, 101 Perimeter Road, Saskatoon, Sask. Canada S7N OX4 P. F. Bernath Department of Chemistry, University of Waterloo, Waterloo, Ont., Canada N2L 3G1

2. Introduction “The CN radical has been the subject of extensive studies because of its importance in chemical kinetics, flame diagnostics, and astrophysics. The CN radical is found in many extraterrestrial sources including the Sun, stellar atmospheres, comets, dark interstellar clouds, and diffuse interstellar clouds.” from Ram et al. JMS, 237, 247 (2006).

3. Interstellar CN Violet 0-0 Diffuse interstellar cloud absorption towards the star HD169454 Gredel et al. AA, 251, 625 (1991) See also, A. McKellar, PASP, 52, 187 (1940) (Bob McKellar’s father!) T rot = 3 K (same temperature as the cosmic background radiation) [CN]/[ 13 CN]=38

4. Circumstellar CN Violet 0-0 Circumstellar cloud absorption towards the star HD56126 Bakker & Lambert, ApJ 502, 417 (1998) T rot = 12 K [CN]/[ 13 CN]=38 Lines are saturated.

5. Solar CN Violet (Fraunhofer Lines) Absorption in photosphere of the Sun L. Wallace, Kitt Peak Solar Atlas T rot = 6000 K in the solar photosphere [CN]/[ 13 CN]=90 Same as on Earth

6. Comet Linear CN Violet Emission Notice the “Swings effect” Arpigny et al. Science 301, 1522 (2003) [CN]/[ 13 CN]=115, [CN]/[C 15 N]=140 (269 on Earth)

7. Red Rectangle CN Violet Emission and absorption! Hobbs et al. ApJ 615, 947 (2004)

8. McMath-Pierce Solar Observatory

9. McMath-Pierce FTS

10. CN Violet Δv=+2 Sequence CN was made by S. Davis using a microwave discharge of nitrogen with a trace of methane. The discharge tube was cooled by a flow of N 2 vapor from liquid nitrogen boil-off.

11. CN Violet 10-10 Band

12. CN Data Used Starting point was previous analysis of Prasad & Bernath 1991 (jet-cooled emission data, plus IR and microwave) New microwave: Klisch et al. v=0-7 New IR: Horka et al. 1-0 to 8-7 bands Electronic: Our new B-X data for v’ & v” up to 14 and 15-15 band plus Douglas & Routly, Ito et al. for v’s > 15

13. CN X 2 Σ + Constants

14. CN B 2 Σ + State Constants