Abstract

Theoretical–computational studies together with recent astronomical observations have shown that under extreme conditions in the interstellar medium (ISM), complexes of noble gases may be formed. Such observations have generated a wide range of possibilities. In order to identify new species containing such atoms, the present study gathers spectroscopic data for noble gas hydride cations, NgH+ (Ng = He, Ne, Ar) from high-level ab initio quantum chemistry computations, aiming to contribute in understanding the chemical bonding and electron sharing in these systems. The interaction potentials are obtained from CCSD(T)/CBS and MRCI+Q calculations using large basis sets, and then employed to compute vibrational levels and molecular spectroscopic constants for all known stable isotopologues of ground state NgH+ cations. Comparisons with previously reported values available are discussed, indicating that the present data could serve as a benchmark for future studies on these systems and on higher-order cationic noble gas hydrides of astrophysical interest.

Highlights

  • Given the extreme conditions of temperature and pressure, the interstellar medium (ISM) is a perfect framework to find unconventional molecules that are unthinkable in the Earth’s atmosphere

  • It was thought that noble gas compounds were quite unlikely, as they would react with other elements or molecular systems through weak van der Waals interactions

  • The presence of the HeH+ and ArH+ molecules in ISM has been recently reported for first time in the planetary nebula NGC 7027 (Güsten et al, 2019) and Crab Nebula (Barlow et al, 2013), respectively, while later on, the ArH+ has been detected in extragalactic sources (Müller et al, 2015), and it has been suggested that is ubiquitous in the ISM (Schilke et al, 2014)

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Summary

INTRODUCTION

Given the extreme conditions of temperature and pressure, the interstellar medium (ISM) is a perfect framework to find unconventional molecules that are unthinkable in the Earth’s atmosphere. The HeH+ presence in the ISM has been speculated for a long time, and its detection has been just recently confirmed (Güsten et al, 2019) This cation is the simplest molecular system to treat just isoelectronic with H2, so it has been extensively studied theoretically and experimentally ever since (Wolniewicz, 1965; Kolos, 1976; Kolos and Peek, 1976; Bishop and Cheung, 1979; Bernath and Amano, 1982; Carrington et al, 1983; Crofton et al, 1989; Cencek et al, 1995; Jurek et al, 1995; Liu and Davies, 1997; Matsushima et al, 1997; Coxon and Hajigeorgiou, 1999; Engel et al, 2005; Stanke et al, 2006; Pachucki, 2012; Tung et al, 2012; Perry et al, 2014), including observation of infrared and rotational spectra of its isotopologues, ab initio and high accurate with spectroscopic precision potential curves, and quasibound states calculations. The search of new molecular species that are not stable in the laboratory or that are difficult to synthesize (for example radicals and charged isolated molecules) could be significantly simplified

COMPUTATIONAL DETAILS
Ab initio Electronic Structure Calculations and PECs
Literature
Bound-State Calculations and Molecular Spectroscopic Constants
CONCLUSIONS

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