Millimeter-Wave and High-Resolution Infrared Spectroscopy of 3-Furonitrile.

Area of Science:

• Molecular Spectroscopy
• Astrochemistry
• Quantum Chemistry

Background:

• Understanding the rotational and vibrational spectra of organic molecules is crucial for identifying them in interstellar space.
• 3-Furonitrile, an isomer of 2-furonitrile, has a significant dipole moment that influences its spectral properties.
• Previous studies have characterized some spectral features, but a comprehensive analysis, especially of excited vibrational states, was lacking.

Purpose of the Study:

• To collect and analyze the high-resolution rotational spectrum of 3-furonitrile across a wide frequency range (85–500 GHz).
• To investigate the Coriolis-coupled vibrational states (ν₁₇ and ν₂₄) using both infrared and rotational spectroscopy.
• To provide accurate spectroscopic constants and frequencies for 3-furonitrile to facilitate its detection in radioastronomical observations.

Main Methods:

• High-sensitivity rotational spectroscopy was performed from 85 to 500 GHz, observing over 5600 new transitions.
• Data from new and existing transitions were fitted using partial-octic, distorted-rotor Hamiltonian models for the ground vibrational state.
• Rotationally resolved infrared (30–600 cm^-1) and pure rotational transitions for the ν₁₇ and ν₂₄ states were analyzed using a Coriolis-coupled, two-state Hamiltonian.

Main Results:

• Over 5600 new rotational transitions were assigned for the ground vibrational state, with a low fitting uncertainty (σ_fit < 0.031 MHz).
• Accurate vibrational frequencies for ν₁₇ (168.193 164 8 (67) cm^-1) and ν₂₄ (169.635 831 5 (77) cm^-1) were determined, along with seven Coriolis-coupling terms.
• The two lowest-energy excited states exhibit a small energy gap and an inversion of relative energies compared to 2-furonitrile.

Conclusions:

• The precise rotational and spectroscopic constants determined for 3-furonitrile provide a robust foundation for its radioastronomical detection.
• The study elucidates the Coriolis-coupling dynamics between the in-plane and out-of-plane nitrile bending vibrations.
• The findings contribute to a deeper understanding of molecular properties relevant to astrochemistry and interstellar medium composition.