| Popis: |
A valence force field, including selected interaction constants, has been used to compute the thirty-three planar vibration frequencies of each of naphthalene, naphthalene-α-d4, naphthalene-β-d4 and naphthalene-d8. Starting with benzene-like force constants, the method of steepest descents was used in an iterative calculation which forced agreement with seven observed Ag-type fundamentals of the undeuterated compound, using (in the more successful of two such calculations) the Ag assignments of Luther. The final force field gave encouraging results when used to calculate all the other frequencies, and appears to be particularly suitable for the contentious low frequencies. The only really large and unavoidable disagreement was found in the case of the particular B2u vibration which carries naphthalene between two Kekule structures. The normal modes are depicted; they are strikingly similar to the modes found by Schmid in a calculation which led to considerably different numerical frequencies. |
