Herschel/HIFI line surveys: Discovery of interstellar chloronium (H{sub 2}Cl{sup +})

Journal Article · Thu Jan 22 04:00:00 EST 2015 · AIP Conference Proceedings

DOI:https://doi.org/10.1063/1.4906690· OSTI ID:22390908

Prior to the launch of Herschel, HCl was the only chlorine-containing molecule detected in the interstellar medium (ISM). However, chemical models have identified chloronium, H{sub 2}Cl{sup +}, as a relatively abundant species that is potentially detectable. H{sub 2}Cl{sup +} was predicted to be most abundant in the environments where the ultraviolet radiation is strong: in diffuse clouds, or near the surfaces of dense clouds illuminated by nearby O and B stars. The HIFI instrument on Herschel provided the first detection of H{sub 2}Cl{sup +} in the ISM. The 2{sub 12}-1{sub 01} lines of ortho-H{sub 2}{sup 35}Cl{sup +} and ortho-H{sub 2}{sup 37}Cl{sup +} were detected in absorption toward NGC 6334I, and the 1{sub 11}-0{sub 00} transition of para-H{sub 2}{sup 35}Cl{sup +} was detected in absorption toward NGC 6334I and Sgr B2(S). The derived HCl/H{sub 2}Cl{sup +} column density ratios, ∼1-10, are within the range predicted by models of diffuse and dense Photon Dominated Regions (PDRs). However, the observed H{sub 2}Cl{sup +} column densities, in excess of 10{sup 13} cm{sup −2}, are significantly higher than the model predictions. These observations demonstrate the outstanding spectroscopic capabilities of HIFI for detecting new interstellar molecules and providing key constraints for astrochemical models.

• OSTI ID: 22390908
• Journal Information: AIP Conference Proceedings, Journal Name: AIP Conference Proceedings Journal Issue: 1 Vol. 1642; ISSN APCPCS; ISSN 0094-243X
• Country of Publication: United States
• Language: English

Related Subjects

74 ATOMIC AND MOLECULAR PHYSICS
ABSORPTION
CHLORINE
DENSITY
HYDROCHLORIC ACID
HYDROGEN
INTERSTELLAR SPACE
LIMITING VALUES
MOLECULAR IONS
MOLECULES
PHOTONS
POTENTIALS
STAR CLUSTERS
SURFACES
ULTRAVIOLET RADIATION