Sequential contact transformation formulation of asymmetric-rotator vibration-rotation Hamiltonian

The sequential contact transformation technique recently described in this journal by Niroomand-Rad and Parker is applied to the Amat-Nielsen expansion of the Darling-Dennison Hamiltonian of asymmetric rotator type molecules. The resulting formalism for the calculation of fourth-order Hamiltonian coefficients is significantly simpler than the conventional Amat-Nielsen contact transformation formalism. Therefore the eventual development of detailed expressions for fourth-order vibration-rotation interaction coefficients in terms of fundamental molecular constants now appears much more feasible.