RAMAN-SCATTERING TENSORS IN THYMINE MOLECULE FROM AN AB-INITIO MO CALCULATION

Ab initio SCF MO calculations have been made of the thymine molecule f or the permanent polarizability and the polarizability derivatives wit h respect to the normal coordinates. The latter correspond to the comp onents of the Raman tensors, and each of these tensors was brought int o a visualized form by a transformation of the tensor axes into the pr incipal system. For a comparison with such computational findings, a p olarized Raman spectroscopic measurement has been made of a single cry stal of thymine with 488.0 nm excitation. For most of the in-plane vib rations, calculated tensors were found to be well correlated with the observed Raman scattering anisotropy. On the basis of such correlation s, discussions are given as for the polarizability oscillations caused by the atomic displacements in the molecule. (C) 1997 Elsevier Scienc e B.V.