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Session 40 - The Interstellar Medium.
Display session, Tuesday, June 09
Atlas Ballroom,

[40.16] The Interstellar Abundances of Tin and Cadmium

U. J. Sofia, K. A. Matthews (Villanova Univ.), D. M. Meyer (Northwestern Univ.)

We have determined interstellar gas-phase abundances of tin and cadmium in diffuse clouds toward 14 and 5 stars respectively. The data used were high signal-to-noise absorption spectra of the Cd \sc ii \lambda2145 Å\space and Sn \sc ii \lambda1400Å\space transitions observed with the HST's Goddard High Resolution Spectrograph. Our results for Sn indicate that this element is exchanged between the gas and dust phases in the diffuse ISM whereas the gas-phase Cd abundance does not appear to depend on the cloud density. Since tin is obviously incorporated into dust, and cadmium is likely to be, the intrinsic (gas + dust) abundances of these elements is not directly measurable.

Tin and cadmium are primarily produced by the s-process in intermediate and low mass AGB stars. When compared to the solar abundances, an intrinsic abundance of these elements in interstellar clouds should provide an empirical determination of s-process yields and the cumulative addition of this material into the ISM over the lifetime of the sun. We will present our preliminary analysis of the intrinsic interstellar abundances of Sn and Cd in our sample and the implications for s-process enrichment. We will use interstellar Ge and Zn depletion measurements (elements in the same columns of the periodic table as Sn and Cd) to estimate the abundances of Sn and Cd incorporated into interstellar grains.

This work has been supported by the HST grants GO-6541 and GO-6070, and the NASA-LTSARP grant NAG5-3539 to Villanova University.

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