ULTRAVIOLET TRANSITIONS OF LOW CONDENSATION TEMPERATURE HEAVY-ELEMENTS AND NEW DATA FOR INTERSTELLAR ARSENIC, SELENIUM, TELLURIUM, AND LEAD

We report on the first interstellar detections of transitions of the heavy elements As II and Se II along with 2 sigma upper limits for Te II and Pb II. We also present a line list of the strongest ultraviolet transitions for an additional eight heavy elements, including rest wavelengths and a compilation of existing transition oscillator strengths along with new theoretical values for many species. All these transitions fall within the accessible UV range of the Goddard High Resolution Spectrograph. With two exceptions, all these elements are characterized by relatively low condensation temperatures (T(c) less-than-or-equal-to 720 K) and are therefore expected to be only lightly depleted onto dust. Because these elements are produced by a diverse mixture of slow and rapid neutron capture (s- and r-process), comparisons involving their measured abundances for different sight lines provide a unique probe of stellar evolution, nucleosynthetic enrichment, and the efficiency with which this material is mixed in the interstellar medium.