On the Detectability of the HSS, HSO, and HOS Radicals in the Interstellar Medium

Abstract

Abstract HSS has yet to be observed in the gas phase in the interstellar medium (ISM). HSS has been observed in cometary material and in high abundance. However, its agglomeration to such bodies or dispersal from them has not been observed. Similarly, HSO and HOS have not been observed in the ISM, either, even though models support their formation from reactions of known sulfur monoxide and hydrogen molecules, among other pathways. Consequently, this work provides high-level, quantum chemical rovibrational spectroscopic constants and vibrational frequencies in order to assist in interstellar searches for these radical molecules. Furthermore, the HSO−HOS isomerization energy is determined to be 3.63 kcal mol−1, in line with previous work, and the dipole moment of HOS is 36% larger at 3.87 D than HSO, making the less stable isomer more rotationally intense. Finally, the S−S bond strength in HSS is shown to be relatively weak at 30% of the typical disulfide bond energy. Consequently, HSS may degrade into SH and sulfur atoms, making any ISM abundance of HSS likely fairly low, as recent interstellar surveys have observed.