The infrared spectrum of the Ne-C2D2 complex

Area of Science:

• Molecular Spectroscopy
• Intermolecular Forces
• Quantum Chemistry

Background:

• Weakly bound complexes like Ne-C2D2 are crucial for understanding van der Waals interactions.
• Previous studies on similar systems (Ne-C2H2, Ne-C2HD) had limited infrared spectral assignments.
• The Ne-C2D2 system approaches the free rotor limit, complicating spectral analysis.

Purpose of the Study:

• To observe and assign infrared spectra of Ne-C2D2 in the ν3 fundamental band region.
• To provide a more complete spectral analysis than previously reported for Ne-C2H2 and Ne-C2HD.
• To reassign existing microwave transitions and compare experimental data with theoretical predictions.

Main Methods:

• Utilizing tunable optical parametric oscillator spectroscopy on a pulsed supersonic slit jet expansion.
• Employing predicted rotational energies from ab initio intermolecular potential energy surfaces for spectral assignment.
• Analyzing spectra up to the j = 3←2 band, labeling C2D2 rotation within the dimer.

Main Results:

• Detailed infrared spectra of Ne-C2D2 were obtained and assigned, extending to higher rotational states (j=3).
• Previously reported microwave transitions for the j=1 state of Ne-C2D2 were reassigned.
• Experimental spectral variations with C2D2 vibrational excitation were compared to theoretical calculations.

Conclusions:

• The study provides a comprehensive infrared spectral analysis of Ne-C2D2, surpassing previous work on related systems.
• The comparison between experimental spectra and theoretical predictions highlights the need for vibrational averaging in theoretical models.
• This work advances the understanding of intermolecular interactions in weakly bound complexes and refines theoretical approaches.