Knowledge Bank

The general Hamiltonian for a rotating asymmetric rotor molecule with internal rotation can be written as $$\hat{H}= \tilde{P}\mu(\tau)P + (p_{\tau} - \tilde{P}p(\tau) F(\tau)(p_{t\tau} - \tilde{\rho}(\tau)P) + V(\tau) + \hat{H}_{h},$$ where $H¯h$ contains the higher order terms of the components of the angular momentum. This Hamiltontan has been transformed according to $H~=\exp (-iS^)H^\exp (iS^)$ with an appropriate operator S to bring the Hamiltonian into a reduced form. The qualitative features (order of terms, symmetry) of various reduction schemes are described and discussed (relation to PAM, IAM) and the numbers of determinable parameters are given. Detailed examples are presented for the reduction of pure internal rotor Hamiltonians.