AAS 206th Meeting, 29 May - 2 June 2005
Session 32 Highlights in Laboratory Astrophysics
Poster, Wednesday, 10:00am-7:00pm, Thursday, 9:20am-2:00pm, June 1, 2005, Ballroom A

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[32.08] Sub-millimeter Spectroscopy of Diatomic Hydrides of Astrophysical Interest

D. T. Halfen (Univ. of Arizona), C. S. Savage (JILA), A. J. Apponi, L. M. Ziurys (Univ. of Arizona)

One class of interstellar molecules that are unique to the millimeter/far-infrared region of the electromagnetic spectrum are diatomic hydrides. These species have low moments of inertia, and therefore their rotational spectrum lies exclusively at sub-millimeter wavelengths and shorter. They are therefore extremely good targets for space-borne and airborne platforms such as Herschel, SOFIA, and SAFIR. Diatomic hydrides, both neutral (MH) and ionic (MH+) forms, are also basic building blocks of interstellar chemistry. In ionic form, they may be the "hidden" carriers of refractory elements in dense gas. To date, there is very little high resolution data available for many hydride species, in particular the ionic form. In the Ziurys laboratory, we have been conducting studies of metal hydrides using sub-millimeter direct absorption and velocity modulation techniques. We have measured the pure rotational spectrum of AlH (J = 0 arrow 1), CrH (N = 0 arrow 1), and SH+ (N = 0 arrow 1). The hydride neutrals were created in a DC discharge of H2 and metal vapor, generated in a Broida-type oven. In the case of AlH (X1\Sigma+), the quadrupole hyperfine splitting in the J = 0 arrow 1 transition was significantly revised from past measurements. The strongest five hyperfine transitions were recorded for CrH (X6\Sigma+) in its N = 0 arrow 1 transition, the first direct observation of these lines. Spectra of AlD and CrD were measured as well. Finally, the N = 0 arrow 1 transition of the SH+ ion (X3\Sigma-) has been recorded. For this molecule, an AC discharge of H2S and argon or CH3SH and argon was used for the synthesis, and velocity modulation methods were employed to isolate ion signals. Currently, velocity modulation techniques are being developed to study other diatomic hydride ions. Results of these investigations will be reported. This work is supported by NASA Grant NAG5-12719.

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