The (3, 3) metastable rotational level of H 3 + Takeshi Oka Department of Chemistry and Department of Astronomy and Astrophysics The Enrico Fermi Institute, The University of Chicago New Horizon of Astrochemistry and Laboratory Spectroscopy March 16, 9 am, 2006 I am looking for a postdoc, Laboratory or Observatory

Metastable rotational levels J K NH 3

Lifetime of the Universe ?

Metastable rotational levels J K NH 3

Breakdown of symmetry ΔK = 0 ΔK = 3 Geometry C 3 Permutation (123) selection rules

Metastable rotational levels J NH 3 μ T. Oka, F. O. Shimizu, T. Shimizu, J. K. G. Watson, ApJ 165, L15 (1971) 50 years 人生五十年人生五十年 Δk = years F. Y. Chu, T. Oka, J. Chem. Phys. 60, 4612 (1974) PH 3 AsH 3

H 3 + is simpler J Δk = 3 H3+H3+ Non-polar No inversion

J K 32.9 K 361 K (J, K) The ideal energy levels of H 3 + (3, 3) metastable level (1, 1) ground level Δk = ± 3 forbidden transitions 27.2 days (2, 2) unstable level (1, 0) 0 ±1 ±2 ±3 k N crit ~ 200 cm -3 H H 2 → (H 5 + )* → H H 2 Pan, Oka, ApJ 305, 518 (1986)

Discovery of metastable interstellar H 3 + Goto, McCall, Geballe, Usuda, Kobayashi, Terada, Oka PASJ, 54, 951 (2002) (3, 3) metastable Subaru telescope (1, 1) ground level

Sightline toward the Galactic center The Central Molecular Zone

J K 32.9 K 361 K (J, K) Thermalization of H 3 + (3, 3) metastable level (1, 1) ground level 27.2 days (2, 2) unstable level (1, 0) 0 ±1 ±2 ±3 k N crit ~ 200 cm -3 H H 2 → (H 5 + )* → H H 2

Radiation Collision Reaction Rigorous Selection Rules Approximate Rules Random ortho  para ΔI = 0 ortho  para ΔI = 0 ΔI total = 0 AAAA BBBB CACA DBDB Ψ’ψΨ’ψ T rad  3 K « T kin Elementary processes

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 Oka, Epp ApJ, 613, 349 (2004)

Discovery of hot and diffuse clouds Oka, Epp, ApJ 613,349 (2004) Oka, Geballe, Goto, Usuda, McCall, ApJ 632, 882 (2005)

(1, 1) ground level CMZ and spiral arms (3, 3) metastable level All CMZ (2, 2) unstable level Neither CO Mostly spiral arms High temperature Low density Enter Gemini South Observatory

The Expanding Molecular Ring Kaifu, Kato, Iguchi, Nature (1972) Scoville, ApJ (1972) Whiteoak, Gardner, MNRAS (1979)

The central 30 pc of the CMZ Yusef-Zadeh, Morris, AJ (1987) Nagata et al. (1990) Okuda et al. (1990) The Quituplet

Oka, Geballe, Goto, Usuda, McCall, ApJ (2005) Other stars

Controversies T. Oka No hot gas in the Expanding Molecular Ring F. Le PetitDiffuse gas cannot be that hot J. BlackInfrared pumping (1, 0) (3, 0) (2, 0) (3, 3) F. Yusef-Zadeh 4 categories of gases ApJ 637, L101 (2006)

The Galactic center The Central Molecular Zone (CMZ) The treasure house of H 3 + Discovery of metastable H 3 + Revelation of warm and diffuse gas Cold 30 K >10 4 cm -3 Hot 10 4 K ~10 2 cm -3 Ultrahot K ~0.3 cm -3 Warm 250 K ~10 2 cm -3 CO, CSX-ray H3+H3+ Radio diffraction Volume filling factor f ~ 0.5 «1 0.01

Extragalactic H 3 + Geballe, Goto, Usuda, Oka, McCall ApJ in press Z =

The (3, 3) metastable rotational level of H 3 + Takeshi Oka Department of Chemistry and Department of Astronomy and Astrophysics The Enrico Fermi Institute, The University of Chicago New Horizon of Astrochemistry and Laboratory Spectroscopy March 16, 9 am, 2006 I am looking for a postdoc, Laboratory or Observatory

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)  Per Surprise!! H 3 + more abundant in diffuse clouds!! N(H 3 + ) ~ 3.6 ×10 12 cm -2 A V N(H 3 + ) ~ 4.4 ×10 13 cm -2 A V

Central Molecular Zone, the treasure house of H 3 + M ~ 5 × 10 7 M ⊙ Dominantly molecular Dense clouds, n(H 2 ) > 10 4 cm -4 Volume filling factor 0.1 Hot gas T ~ 300 K High velocity dispersion Low dust temperature T ~ K Mezger, Duschl, Zylka, A&A Rev. (1996) Morris, Serabyn, ARA&A (1996) CMZ

Sightlines toward the CMZ

Extraordinary radio emission Radio Arc –Arched filaments –Nonthermal filaments Sgr A * Yusef-Zadeh, Morris, AJ (1987)