Fitting the Rovibrational Spectra with an Effective Rotational–Large Amplitude Motion Hamiltonian

A general method of solution for the rovibrational problem for a single large amplitude motion coupled to the overall rotation is presented. The numerical construction of the effective rovibrational Hamiltonian is applicable to any semirigid or flexible model for a large amplitude motion. High-order centrifugal distortion and Coriolis interaction terms generated by the small amplitude vibrations of normal modes are effectively included into the Hamiltonian. The method is illustrated by performing a global fit of the rotational transitions observed in the ground and excited states of some typical large amplitude modes.