High Resolution Infrared Spectroscopy of Cyclobutane: A Study of Vibrational ModeCoupling Involving Large Amplitude, Low Frequency Modes

摘要

The high resolution IR spectrum of cyclobutane in a supersonic molecular beam wasobtained for the region of 2981 to 2991/cm. The spectrum reveals four overlapping bands suggestive of vibrational mode coupling in the C-H stretching region. Ground state combination differences demonstrate that these bands originate from 2 different ground states, the symmetric and asymmetric ring puckering states. Evidence of vibrational mode coupling is present in all four bands. The coupling depends on both J and the symmetry of the puckering state. A model coupling scheme involving two qualitatively different types of couplings is developed to explain the observed spectrum. Symmetry restrictions and the Interaction between molecular rotation and ring puckering qualitatively accounts for the dramatically different coupling behavior between the two ring puckering states.