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arXiv · 1711.03344

The Interstellar Formation and Spectra of the Noble Gas, Proton-Bound HeHHe+, HeHNe+, & HeHAr+ Complexes

Cody J. Stephan·Ryan C. Fortenberry
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Abstract

The sheer interstellar abundance of helium makes any bound molecules or complexes containing it of potential interest for astrophysical observation. This work utilizes high-level and trusted quantum chemical techniques to predict the rotational, vibrational, and rovibrational traits of HeHHe+, HeHNe+, and HeHAr+. The first two are shown to be strongly bound, while HeHAr+ is shown to be more of a van der Waals complex of argonium with a helium atom. In any case, the formation of HeHHe+ through reactions of HeH+ with HeH3+ is exothermic. HeHHe+ exhibits the quintessentially bright proton-shuttle motion present in all proton-bound complexes in the 7.4 micron range making it a possible target for telescopic observation at the mid-IR/far-IR crossover point and a possible tracer for the as-of-yet unobserved helium hydride cation. Furthermore, a similar mode in HeHNe+ can be observed to the blue of this close to 6.9 microns. The brightest mode of HeHAr+ is dimmed due the reduced interaction of the helium atom with the central proton, but this fundamental frequency can be found slightly to the red of the Ar-H stretch in the astrophysically detected argonium cation.

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Cody J. Stephan, Ryan C. Fortenberry. 2017-11-09. The Interstellar Formation and Spectra of the Noble Gas, Proton-Bound HeHHe+, HeHNe+, & HeHAr+ Complexes. https://doi.org/10.1093/mnras/stx937

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