Raman Intensities of the A1 Lines of Oxyanions

The trace of the derived polarizability tensor has been measured on an absolute scale for the ions CO3=, NO3—, PO4—3, SO4—2, and ClO4— in aqueous solution. From these and the known normal coordinate matrix elements, the values of the derivative with respect to bond length have been calculated. Results are interpreted in terms of bond order, and indicate appreciable π bonding in the ions NO3—, SO4—2, and ClO4—. In these cases, as opposed to hydrocarbons, a π electron makes a larger contribution to the derived bond polarizability than does a σ electron.