Monday 10 July at 2:30pm

ABSTRACT: "The 1996 UKIRT detection (1) of H3+ in dense molecular clouds toward young stellar objects AFGL2136 and W33A has provided the most direct evidence supporting the ion-molecule reaction scheme of interstellar chemistry. The observed column densities in these and other dense clouds agreed well with model calculations and the dimension, density, and temperature of clouds derived from the observations were all reasonable (2). Our subsequent detection of H3+ in the diffuse interstellar medium toward the Galactic Center and Cygnus OB2 No.12 (3,4), however, were unexpected and introduced a new enigma on the chemistry of the diffuse interstellar medium which is now hotly debated. I shall discuss our observations and analysis together with various poroposals and the result of new observations at the UKIRT on the nights of July 5-7."

(1) TR.Geballe, T.Oka, Nature 384 334 (1996)

(2) BJ McCall, TR Geballe, KH Hinkle, T Oka, ApJ 512 338 (1999)

(3) TR Geballe, BJ McCall, KH Hinkle, T Oka, ApJ 510 251 (1999)

(4) BJ McCall, TR Geballe, KH Hinkle, T.Oka, Science 279 1910 (1998)