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

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.

arXiv comment9 pages, 8 tables

References in corpus (7)

• Detection of a Noble Gas Molecular Ion, {36}ArH^+, in the Crab Nebula
• Ubiquitous argonium (ArH${}^{+}$) in the diffuse interstellar medium -- a molecular tracer of almost purely atomic gas
• High-Accuracy Quartic Force Field Calculations for the Spectroscopic Constants and Vibrational Frequencies of 1 ^1A' l-C3H-: A Possible Link to Lines Observed in the Horsehead Nebula PDR
• Spectroscopic Constants and Vibrational Frequencies for l-C3H+ and Isotopologues from Highly-Accurate Quartic Force Fields: The Detection of l-C3H+ in the Horsehead Nebula PDR Questioned
• The chemistry of interstellar argonium and other probes of the molecular fraction in diffuse clouds
• Photodissociation of interstellar ArH+
• ArH2+ and NeH2+ as Global Minima in the Ar+/Ne+ + H2 Reactions: Energetic, Spectroscopic, and Structural Data

Cited by in corpus (3)

• Energy-transfer Quantum Dynamics of HeH${}^{+}$ with He atoms: Rotationally Inelastic Cross Sections and Rate Coefficients
• The Fundamental Vibrational Frequencies and Spectroscopic Constants of the Dicyanoamine Anion, NCNCN${}^{-}$ (C${}_2$N${}_3^{-}$): Quantum Chemical Analysis for Astrophysical and Planetary Environments
• Formation of Argon Cluster with Proton Seeding