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

N (H 3 + ) in cm A v A v 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 Ζ Per Ubiquitous H 3 + Dense Clouds Diffuse Clouds GC

Galactic plane Quintuplet

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

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

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

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

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

n(3,3)/n(1,1)

n(3,3)/n(2,2)

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

Ortho-H 3 + Para-H 3 + T(H 2 ) = 10 K T(H 2 ) = 60 K K K K

Gemini South

Quasi-metastable 11.4 years

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