Department of Astronomy and Astrophysics, and Department of Chemistry
The Enrico Fermi Institute of the University of Chicago, Ill., USA
Because of the efficient ion-neutral reaction H2+
+ H2 -> H3+
+ H, the H3+ molecular ion is
the most abundantly produced ion in H2 dominated
plasmas. The pure and intense H3+ emission
spectrum from Jovian ionosphere has now been established as a useful probe
for the study of its plasma activity (1). Recently, H3+
with column densities of (1.7 - 5.5) x 1014 cm-2
has been detected in absorption towards the direction of young stellar
objects GL2136, W33A, MonR IRS2, GL961E and GL2591 that are deeply embedded
in molecular clouds(2,3). Quite unexpectedly, H3+
with similar column density has also been detected in diffuse clouds toward
the visible star Cygnus OB2 No. 12 (4), and with higher column density
towards the Galactic Center (5). The H3+
chemistry in these clouds with its astrophysical implication together with
laboratory experiment on the conversion of ortho- and para- H3+
(6) will be discussed.
1. J.E.P. Connerney, T. Satoh, & R.L. Baron, Icarus 132, 24, 1 (1996).
2. T.R. Geballe & T. Oka, Nature 384, 334 (1996).
3. B.J. McCall, T.R. Geballe, & T. Oka, manuscript in preparation.
4. B.J. McCall, T.R. Geballe, K.M. Hinkle, & T. Oka, Science 279,
1910 (1998).
5. T.R. Geballe, B.J. McCall, K.M. Hinkle, & T. Oka, Astrophys.
J., in press.
6. D. Uy, M. Cordonnier, & T. Oka, Phys. Rev. Lett. 78, 3844 (1997).