### Abstract

The structures and the vibrational dynamics of the complexes HHe ^{+} _{n} are investigated experimentally (via mass spectrometry (MS)) and at high levels of electronic-structure theory. The MS measurements reveal interesting trends about the stability of the starting members of the HHe ^{+} _{n} family. The computations establish that the basically linear, strongly bound, symmetric triatomic molecular ion He(H ^{+} )He, with an equilibrium H–He distance of 0.925 Å and about 2/3 but at least 1/2 of the positive charge on H, is the molecular core of all of the n ≥ 3 complexes. Definitive quantum-chemical results are obtained for HHe ^{+} and HHe ^{+} _{2} , including the proton affinity of He (computed to be 14, 876 ± 12 cm ^{−1} via the focal-point analysis (FPA) scheme), the FPA isomerisation energy between the two linear isomers of HHe ^{+} _{2} (3826 ± 20 cm ^{−1} ), and the dissociation energy of the HHe ^{+} _{2} ****HHe ^{+} + He reaction, with an FPA estimate of 3931 ± 20 cm ^{−1} . The structural isomers of the He-solvated complexes are discussed up to n=18. A useful notation, [k−l−m]-HHe ^{+} _{n} , is introduced to characterise qualitatively the three possible belts around the He–H ^{+} –He core in HHe ^{+} _{n} (n ≥ 3), where l denotes the number of He atoms in the central belt and k ≥ m denote the number of He atoms in the top and bottom belts. Capping He atoms attached to the belts can be indicated by sub- and superscripts. Several possible indicators of microscopic superfluidity are investigated: He evaporation energies, rotational constants, and vibrational fundamentals.

Original language | English |
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Pages (from-to) | 1559-1583 |

Number of pages | 25 |

Journal | Molecular Physics |

Volume | 117 |

Issue number | 9-12 |

DOIs | |

Publication status | Published - Jun 18 2019 |

### Keywords

- HHe
- HHe
- He-solvated proton
- Microscopic superfluidity
- electronic-structure computations
- mass spectrum

### ASJC Scopus subject areas

- Biophysics
- Molecular Biology
- Condensed Matter Physics
- Physical and Theoretical Chemistry

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## Cite this

*Molecular Physics*,

*117*(9-12), 1559-1583. https://doi.org/10.1080/00268976.2019.1585984