The role of small molecular cations in the chemical flow of the interstellar environments

• Published in: Physical chemistry chemical physics : PCCP Vol. 25; no. 35; pp. 2337 - 23383
• Main Authors: González-Sánchez, Lola, Sathyamurthy, N, Gianturco, Francesco A
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 13.09.2023
• Subjects: Cations; Chemical energy; Chemical reactions; Energy flow; Flow paths; Interstellar chemistry; Interstellar matter; Molecular clouds; Molecular ions; Positive ions; Stellar envelopes
• ISSN: 1463-9076; 1463-9084; 1463-9084
• DOI: 10.1039/d3cp03000h

Molecular ions have been ubiquitous in a variety of environments in the interstellar medium, from Circumstellar Envelopes to Dark Molecular Clouds and to Diffuse Clouds. Their role in the multitude of molecular processes which have been found to occur in those environments has been the subject of many studies over the years, so that we have acquired by now a complex body of data on their chemical structures, their possible function within chemical reactions and their most likely paths to formation. In the present work we review a broad range of such molecular ions, focusing exclusively on positive ions involving the smallest and simplest cations which have been either detected or conjectured as present in the interstellar medium (ISM). We therefore consider mainly molecular cations formed with components like H, H + , He and He + , atomic species which are by far the most abundant baryons in the ISM in general. Their likely structures and their roles in a variety of chemical energy flow paths are discussed and presented within the context of their interstellar environments. Formation and destruction channels for HeH + are superimposed on this image depicting NGC 7027, or the "Jewel Bug" nebula, where it has been detected recently. Image by NASA, ESA, and J. Kastner (RIT).