Radio frequency and microwave spectroscopy of the HCCH-CO2 and DCCD-CO2 van der Waals complexes

Molecular beam electric resonance spectroscopy has been used to study HCCH–CO2 and DCCD–CO2, giving the following results for HCCH–CO2: A=8875 MHz, B=2861.45 MHz, C=2156.25 MHz, DJ =12.4 kHz, DJK =36.7 kHz, and d1=−3.25 kHz. The permanent dipole moment is 0.1611 D. The equilibrium geometry has the monomers parallel to one another in a configuration having C2v symmetry. Deuterium eQq data provide information on rms vibrational amplitudes and also gives an estimate of 40 cm−1 for the out of plane bending mode. The monomer–monomer stretching vibration is estimated to be 75 cm−1 from the DJ measurement.