High-Level Rovibrational Calculations on Ketenimine

Area of Science:

• Astrochemistry
• Quantum Chemistry
• Molecular Spectroscopy

Background:

• Ketenimine (CH2CNH) is a complex organic molecule (COM) detected in star-forming regions like Sagittarius B2(N).
• It is considered a potential building block for biologically relevant molecules.
• Existing experimental data for ketenimine's spectrum is limited, especially at higher energy ranges (above 1200 cm-1).
• High-level ab initio calculations for ketenimine and its isotopologues are scarce.

Purpose of the Study:

• To provide the first comprehensive, high-level quantum chemical calculations for ketenimine (CH2CNH).
• To thoroughly analyze the full rovibrational spectrum of ketenimine and its isotopologues.
• To generate accurate rovibrational infrared intensities.

Main Methods:

• Explicitly correlated coupled-cluster calculations with up to 4-mode coupling terms were used to obtain potential energy surfaces.
• Variational calculations employing rovibrational configuration interaction (RVCI) theory were performed.
• Dipole moment surfaces were determined using the distinguishable cluster approximation to calculate infrared intensities.

Main Results:

• Accurate quantum chemical calculations and a detailed analysis of the full rovibrational spectrum of ketenimine were achieved.
• Strong Fermi resonances were identified across all isotopologues.
• The calculated spectra were compared with experimental data, validating the theoretical results.
• Very strong Coriolis coupling effects were observed in the ketenimine system.

Conclusions:

• The study presents the first high-level theoretical data for the ketenimine (CH2CNH) rovibrational spectrum.
• The findings validate existing experimental data and offer new insights into ketenimine's spectral properties.
• The identified resonances and coupling effects are crucial for understanding ketenimine's role in astrochemical environments.