Calculated octic centrifugal distortion coefficients of non-linear molecules

The equilibrium octic centrifugal distortion coefficients of a molecule are coefficients of terms of the type H˜08 in the expansion of the effective Hamiltonian. They depend on the quartic potential constants kklmn′ for the vibrational modes that have non-zero inertial derivatives, and therefore give information on these constants additional to that given by the other terms that depend on the quartic potential, H˜24 and H˜40. The present work describes the calculation of these H˜08 terms from a given potential by perturbation theory, using a computer program that calculates the coefficients in the successive contact transformations. Results are presented for the SO2, ClO2, O3, and H2O molecules.