1. Interstellar H 3 + in Metastable Rotational Levels Takeshi Oka and Erik Epp Department of Chemistry and Department of Astronomy and Astrophysics, The Enrico Fermi Institute, The University of Chicago the 58 th International Symposium on Molecular Spectroscopy Columbus Ohio, FA06,10:27, June 20, 2003

2. Δk = 3 Forbidden Rotational Transitions in H 3 + Interstellar NH 3 Oka, Shimizu, Shimizu, Watson, ApJ 165, L15 (1971) General Theory Watson, J. Mol. Spectrosc. 40, 536 (1971) H 3 + Pan, Oka, ApJ 305, 518 (1986) Ab initio H 3 + Neale, Miller, Tennyson, ApJ 335, 486 (1988) μ

3. Δk = 3 Forbidden Rotational Transitions in H 3 + Interstellar NH 3 Oka, Shimizu, Shimizu, Watson, ApJ 165, L15 (1971) Theory Watson, J. Mol. Spectrosc. 40, 536 (1971) 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 15.8 hours 7.9 hours 3.8 hours μ

4. Quasi-metastable 11.4 years

5. 4000 cm -1 2000 cm -1 0

6. Radiation Collision Reaction Rigorous Selection Rules Approximate Random ortho  para ΔI = 0 ortho  para ΔI = 0 ΔI total = 0 +  - ΔJ = ± 1, 0 AAAA BBBB CACA DBDB

7. 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

12. Ortho-H 3 + Para-H 3 +