Cationic Noble-Gas Hydrides: From Ion Sources to Outer Space

Area of Science:

• Physical Chemistry
• Astrochemistry
• Quantum Chemistry

Background:

• Cationic species with noble gas (Ng)-hydrogen bonds are fundamental to the gas-phase ion chemistry of Group 18 elements.
• The study of these species dates back over 90 years with the initial detection of HeH+ and HeH from ionized He/H2 mixtures.
• The family of Ng-H cations has expanded significantly, attracting substantial experimental and theoretical investigation.

Purpose of the Study:

• To review the current knowledge on the structure, stability, and formation pathways of noble gas-hydrogen cations.
• To highlight the recent discovery of diatomic ArH+ and HeH+ in galactic and extragalactic regions.
• To explore the implications of these findings for understanding the role of Ng-H cations in outer space.

Main Methods:

• Review of existing experimental data on noble gas-hydrogen cations.
• Analysis of theoretical calculations concerning the structure and stability of these species.
• Compilation of astronomical observations detecting ArH+ and HeH+ in extraterrestrial environments.

Main Results:

• Noble gas-hydrogen cations exhibit diverse bonding motifs and are key players in gas-phase ion chemistry.
• Recent astronomical detections of ArH+ and HeH+ provide a new context for laboratory studies.
• These findings raise intriguing questions about the extraterrestrial significance of Ng-H cations.

Conclusions:

• Noble gas-hydrogen cations are important chemical species with implications extending to astrochemistry.
• The review synthesizes current understanding of their fundamental properties and formation.
• Future research should bridge laboratory findings with astronomical observations to fully elucidate their cosmic role.