Ab Initio Characterization of the [H₂,C,N,O]⁺ Isomeric System: Structures, Spectroscopy, and Electronic States

Area of Science:

• Astrochemistry
• Theoretical Chemistry
• Computational Quantum Chemistry

Background:

• Protonated species are crucial in ion-molecule reactions within astrochemical environments.
• Understanding the structures and properties of protonated molecules is essential for interpreting observational data.

Purpose of the Study:

• To theoretically characterize the low-lying isomers of the [H,H,C,N,O]+ system.
• To accurately predict spectroscopic parameters for potential identification in laboratory and astrophysical settings.

Main Methods:

• High-level theoretical calculations using coupled-cluster (CC) theory.
• Exploration of the ground-state potential energy surface.
• Composite schemes for determining equilibrium structures, relative energies, and spectroscopic properties.

Main Results:

• Identification of ten protonated isomers of [H,H,C,N,O]+.
• Confirmation of H2NCO+ and HNCOH+ as the two most stable isomers.
• Accurate prediction of rotational spectroscopy parameters, vibrational frequencies, and infrared intensities for all isomers.

Conclusions:

• The predicted properties will aid in the identification of these protonated species in laboratory and astrophysical media.
• The study provides valuable data for understanding ion-molecule chemistry in space.
• Electronic state patterns with valence-Rydberg character are also presented.