2. The Non-Thermal Rotational Distribution of Interstellar H 3 + (ApJ, in press ) Takeshi Oka and Erik Epp, Department of Astronomy and Astrophysics, and Department of Chemistry, The Enrico Fermi Institute, The University of Chicago 59 th Ohio State University In ternational Symposium on Molecular Spectroscopy, RI 05, 2:51 pm, June 24, 2004

3. 8 6 4 2 0 N (H 3 + ) in 10 14 cm -2 16012080400 A v 151050 A v 8 6 4 2 0 Dense Clouds Diffuse Clouds GC Dense clouds McCall, Geballe, Hinkle Oka, ApJ 522,338(1999) Diffuse clouds McCall, Hinkle, Geballe, Moriarty-Schieven, Evans, Kawaguchi, Takano, Smith, Oka, ApJ 567, 391 (2002) W33A AFGL2136 AFGL 2591 AFGL 490 AFGL 961E MonR2 IRS3 Cygnus OB2 #12 WR 118 # 5 WR 104 WR 121 HD 20041 183143 Ζ Per Ubiquitous H 3 + Dense Clouds Diffuse Clouds GC

4. Galactic plane Quintuplet

5. H 3 + toward the Galactic center N(H 3 + )= 17.5(3.9) × 10 14 cm -2 GC IRS 3 27.7(2.4)  10 14 cm -2 GCS 3-2 Geballe, McCall, Hinkle, Oka, ApJ 510, 251 (1999) GC IRS 3

6. Δk = 3 Forbidden Rotational Transitions in H 3 + Interstellar NH 3 Oka, Shimizu, Shimizu, Watson, ApJ 165, L15 (1971) Interstellar H 3 + Pan, Oka, ApJ 305, 518 (1986) Theory H 3 + Neale, Miller, Tennyson, ApJ 335, 486 (1988) Metastable 27.2 days 20.4 days μ Critical Density 200 cm -3

8. R(3, 3) l R(2, 2) l (3, 3) (2, 2) Very Non-thermal

9. Radiation Collision Reaction Rigorous Selection Rules Approximate Rules Random +  - ΔJ = ± 1, 0 ortho  para ΔI = 0 ortho  para ΔI = 0 ΔI total = 0 AAAA BBBB CACA DBDB Ψ’ψΨ’ψ T rad  3 K « T kin

10. Rate Equations Production Spontaneous emission 4  10 -7 s -1 Collision n(H 2 ) 100 cm -3 10 -7 s -1 Destruction 10 -9 s -1 10 -17 s -1 10 -7 cm 3 s -1 10 -9 cm 3 s -1 H 3 + + H 2  (H 5 + )*  H 3 + + H 2 Detailed balance Cosmic ray ionization Dissociative recombination Proton hop reaction 0 = Steady State

11. n(3,3)/n(1,1)

12. n(3,3)/n(2,2)

15. T ex from n(1,0)/n(1,1)

16. Ortho-H 3 + Para-H 3 + T(H 2 ) = 10 K T(H 2 ) = 60 K 0 32.86 K 151.33 K 249.26 K

17. Gemini South

18. Quasi-metastable 11.4 years

20. Summary Metastable level (3, 3) populated Unstable levels (2, 2) and (2, 1) unpopulated Spontaneous emission, chemical collision High Temperature (T> 200 K) Low density (n< 100 cm -3 ) Other metastable levels (4, 4), (5, 5), (6, 6) More observations of unstable levels