The Ethylene-Carbon Dioxide Complex and the Double Rotor Model.

Area of Science:

• Molecular Spectroscopy
• Intermolecular Forces
• Quantum Chemistry

Background:

• Weakly bound complexes provide insights into non-covalent interactions.
• Previous studies on C2H4-CO2 complexes revealed complex spectral patterns.

Purpose of the Study:

• Investigate the infrared spectrum of the C2H4-CO2 complex near the CO2 nu3 fundamental band.
• Explain the observed irregular K-subband spacing using theoretical models.

Main Methods:

• High-resolution infrared spectroscopy using a tunable OPO laser.
• Probing a pulsed supersonic slit jet expansion of the C2H4-CO2 complex.
• Analysis of K-subband spacing in the perpendicular (Delta K = +/-1) spectrum.

Main Results:

• Observed irregular K-subband spacing in the nu3 (CO2) band spectrum.
• The spectral pattern differed significantly from previous C2H4-CO2 band studies.
• The "double internal rotor" model successfully explained the observed spectral irregularities.

Conclusions:

• The "double internal rotor" model is validated for explaining the dynamics of the C2H4-CO2 complex.
• The symmetry of the upper vibrational state (nu3 of CO2) is crucial for spectral interpretation.
• This study refines our understanding of intermolecular interactions in weakly bound complexes.