A LABORATORY APPROACH TO THE INTERSTELLAR SULFIDE DUST PROBLEM

In this Letter we communicate optical data of Mg-Fe sulfides in the wa velength range from 10 to 500 mum. The sulfides were prepared in our l aboratory in order to test the tentative identification of a prominent circumstellar emission band at 30 mum observed in carbon-rich AGB sta rs, protoplanetary, and planetary nebulae with Mg-S vibrations in sulf ide grains. Arguments in favor of the existence of an interstellar sul fide dust component consisting of FeS or iron-rich Mg-Fe sulfides are discussed. Model calculations for the source IRC + 10216 based on the communicated optical data demonstrate their practical use. The possibi lities for the observational detection of interstellar FeS bands are c onsidered.