Fourier transform microwave spectrum of CO-dimethyl ether

Area of Science:

• Physical Chemistry
• Molecular Spectroscopy
• Intermolecular Forces

Background:

• Understanding the structure and dynamics of weakly bound molecular complexes is crucial for advancing chemical physics.
• Dimethyl ether (DME) is a key molecule in atmospheric chemistry and serves as a model for studying van der Waals interactions.
• Carbon monoxide (CO) is a simple diatomic molecule with significant astrophysical relevance.

Purpose of the Study:

• To characterize the structural and dynamic properties of the carbon monoxide-dimethyl ether (CO-DME) complex.
• To investigate the internal rotation of CO with respect to DME and the methyl tops of DME.
• To determine the intermolecular potential and dissociation energy of the CO-DME complex.

Main Methods:

• High-resolution Fourier transform microwave spectroscopy was employed to observe rotational transitions.
• Analysis utilized an asymmetric-rotor Hamiltonian and a phenomenological Hamiltonian for simultaneous fitting.
• Rotational constants and inertial defects were calculated to determine structural parameters.

Main Results:

• Rotational transitions for CO-DME, (13)CO-DME, and C(18)O-DME were assigned.
• The heavy-atom skeleton was found to be essentially planar with pseudoinertial defects of -5.764(23) and -5.753(16) uA(2).
• The CO-DME distance was determined to be 3.682 Å, with the CO-a-inertial axis angle at 75.7°, and the V(3) potential barrier was found to be 772(2) cm(-1).

Conclusions:

• The study provides a detailed structural and dynamical characterization of the CO-DME complex.
• The determined parameters offer insights into the nature of intermolecular forces between CO and DME.
• The dissociation energy was estimated to be 1.6 kJ mol(-1), comparable to similar noble gas-DME complexes.