Abstract
Abstract
In the denser and colder regions of the interstellar medium (ISM), gas-phase sulfur is depleted by 2 or 3 orders of magnitude with respect to its cosmic abundance. Thus, which species are the main carriers of sulfur is an open question. Recent studies have proposed S
n
species as potential sulfur reservoirs. Among the various sulfur allotropes, the most stable one is the S8 ring, detected in the asteroid Ryugu and Orgueil meteorite. Shorter species, namely S3 and S4, have been found in the comet 67P/C-G, but their presence in the ISM remains elusive. In this study, we compute the binding energies (BEs) of S
n
(n = 1–8) species on an amorphous water-ice surface model and analyze their infrared (IR) and Raman spectral features to provide data for their identification in the ISM. Our computations reveal that these species exhibit lower BEs than previously assumed and that their spectral features experience minimal shifts when adsorbed on water ice, because of the weak and nonspecific S
n
–ice interactions. Furthermore, these species display very low IR band intensities and, therefore, very accurate instruments operating in the mid-IR range are required for detecting the presence of these species in dense interstellar environments.
Funder
H2020 Excellent science
EC ∣ ERC ∣ HORIZON EUROPE European Research Council
Agenzia Spaziale Italiana
Ministero dell'Università e della Ricerca
Ministerio de Ciencia e Innovación
Publisher
American Astronomical Society