Structure and vibrational dynamics of the CO2dimer from the subhyphen;Doppler infrared spectrum of the 2.7 mgr;m Fermi diad

摘要

Subhyphen;Doppler infrared spectra of two Fermi resonance coupled bands of carbon dioxide dimer have been obtained at 3611.5 and 3713.9 cmminus;1using an optothermal molecular beam colorhyphen;center laser spectrometer. The band origins for the complexes are red shifted by approximately 1 cmminus;1from the corresponding ngr;1+ngr;3/2ngr;02+ngr;3CO2bands. The higher frequency band is perturbed while the lower frequency band appears free of extraneous perturbations as determined from a precision fit to a Watson asymmetric rotor Hamiltonian. This fit and the observed nuclear spin statistical weights reveal that the complex is planar withC2hsymmetry. The Chyphen;hyphen;C separation and Chyphen;hyphen;Cndash;O angle are determined to be 3.599(7) Aring; and 58.2(8)deg;, respectively. The nearest neighbor Ohyphen;hyphen;C distance is 3.14 Aring; which is the same as that found in the crystal. From the centrifugal distortion analysis the weak bond stretching and symmetric bending frequencies are estimated to be 32(2) and 90(1) cmminus;1. No interconversion tunneling is observed.