ArCH₂⁺ : A Detectable Noble Gas Molecule.

Area of Science:

• Computational Chemistry
• Spectroscopy
• Astrochemistry

Background:

• The noble gas molecular cation, ArCH₂⁺, has been observed in mass spectrometry.
• Understanding the spectroscopic properties of such species is crucial for their in-situ detection and characterization.

Purpose of the Study:

• To provide high-level quantum chemical predictions for the vibrational and rotational spectroscopic data of ArCH₂⁺.
• To facilitate the laboratory observation of this organo-noble gas molecule.

Main Methods:

• High-level quantum chemical calculations were employed to predict spectroscopic parameters.
• Analysis focused on vibrational frequencies, rotational constants, and dipole moment.

Main Results:

• A bright fundamental vibrational frequency for the Ar-C stretch was predicted at 421.2 cm^-1 for the ³⁶Ar isotope.
• The molecule exhibits a near-prolate nature and a 2.91 D dipole moment, suitable for submillimeter detection.
• The predicted Ar-C bond strength exceeds that of the experimentally known ArOH⁺ cation.

Conclusions:

• The predicted spectroscopic data suggest that the infrared spectrum of ArCH₂⁺ is observable.
• This molecule may already exist, undetected, in existing spectral data from hydrocarbon cations in argon-matrix experiments.