dc.creator Oka, T. en_US dc.creator Epp, Erik en_US dc.date.accessioned 2006-06-15T20:52:24Z dc.date.available 2006-06-15T20:52:24Z dc.date.issued 2004 en_US dc.identifier 2004-RI-05 en_US dc.identifier.uri http://hdl.handle.net/1811/21341 dc.description $^{a}$ M. Goto, B. J. McCall, T. R. Geballe, T. Usuda, N. Kobayashi, H. Terada and T. Oka, PASJ 54, 951 (2002) $^{b}$ T. R. Geballe, and T. Oka, unpublished $^{c}$ J. K. G. Watson, J. Mol. Spectrosc. 40, 536 (1973) $^{d}$ F. -S. Pan and T. Oka, ApJ 305, 518 (1986) $^{e}$ L. Neale, S. Miller, and J. Tennyson, ApJ 464, 516 (1996) en_US dc.description Author Institution: Department of Chemistry and Department of Astronomy and Astrophysics, the Enrico Fermi Institute, the University of Chicago en_US dc.description.abstract The recent detection of the $R(3,3)^{l}$ absorption line of $H^{+}_{3}$ toward the Galactic center infrared sources GCS 3-2 and GC IRS $3 ^{a,b}$ has demonstrated a remarkable non-thermal rotational distribution of $H^{+}_{3}$. In cloud components which accommodates high $H^{+}_{3}$ column density on the order of $3 \times 10^{15} cm^{-2}$, the $(J, K) = (3, 3)$ level which is 361.5 K above the lowest (1,1) level is populated with a comparable abundance as the (1,1) level, while $H^{+}_{3}$ in the (2,2) level only 151.3 K above is not detectable. This highly non-thermal distribution is the result of a fast spontaneous emission $(2, 2) \to (1, 1)$ with the lifetime of 27.2 days due to centrifugal distortion induced dipole $moment^{c}$ and the metastability of the (3,3) level from which spontaneous emission is $forbidden.^{d}$ In order to understand the observed non-thermal distribution and to plan strategy for observing $H^{+}_{3}$ in higher metastable rotational levels (4,4), (5,5) and (6,6), we have conducted a model calculation on the $H^{+}_{3}$ equilibration in which spontaneous emissions and collision-induced rotational transitions are treated with steady state approximation. Accurately calculated Einstein coefficients of Neale, Miller and $Tennyson^{e}$ are used. Rates of collision-induced rotational transitions were estimated on the assumption of complete random collisional selection rules based only on the principle of detailed balancing. The results show that the preliminary observed values of $n(3,3)/n(1,1) \sim 1$ and $n(3,3)/n(2,2) \geq 5$ indicate an environment with high cloud temperature of $T \geq 300 K$ and low density $n(H_{2}) \leq 50 cm^{-3}$. They also suggest that observations of $H^{+}_{3}$ in higher metastable levels are realistic. en_US dc.format.extent 473580 bytes dc.format.mimetype image/jpeg dc.language.iso English en_US dc.publisher Ohio State University en_US dc.title NON-THERMAL ROTATIONAL DISTRIBUTION OF INTERSTELLAR $H^{+}_{3}$ en_US dc.type article en_US
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