DERIVATION OF ROTATION-VIBRATION HAMILTONIANS THAT SATISFY THE CASIMIR CONDITION

A general prescription for deriving rotation-vibration Hamiltonians th at satisfy the Casimir condition is presented. This condition, achieve d using the Eckart constraints, is that there is no vibrational angula r momentum in the molecular equilibrium configuration. The Eckart cond ition, while useful for studying rotation-vibration inter-actions, is difficult to apply for coordinates other than rectilinear normal coord inates. The present derivation allows one to derive Hamiltonians in cu rvilinear coordinates, yet still take advantage of the most relevant p roperly of the Eckart frame, this being that Coriolis coupling is mini mized in the limit of small vibrations. (C) 1997 American Institute of Physics.