Knowledge Bank

The 1e-2e torsional band of the near prolate asymmetric rotor p-cresol shows a significantly broadened structure in comparison to the electronic origin 0a1-0a1. This broadening is due to an interaction between the torsional vibration of the methylgroup and the overall rotation of the molecule, which is absent in the case of the electronic $origin1$. This interaction is strong, because the axis of internal rotation (z) and overall rotation (a) nearly coincide in the case of p-cresol. A simulation of the rotational band contour of the le-2e band, including this interaction leads to the following rotational constants [$cm-1$]: $A\prime \prime =0.183603B\prime \prime =0.048573C\prime \prime =0.038685A\prime =0.172803B\prime =0.049173C\prime =0.038525$ Within the error these are the same rotational constants as obtained by simulation of the electronic origin Oai-Oai of p-cresol. A simulation of the le-2e band without consideration of the perturbation is only succesfull under the assumption of a very large change of the rotational constant A, which has no physical meaning.