Knowledge Bank

The torsional-rotational energy levels of $CH2DXH$ and $CHD2XH$ have been calculated, where X is either O or S atoms, using an internal axis approach (IAM) for the asymmetric-asymmetric molecules. The internal axis transformation removes the large Coriolis interaction from $HTR$ and places it in the effective $HT$. However, this transformation introduces additional terms into $HTR$ that depend explicitly upon $\propto$. Solution for the energy levels is considered at three stages. First, the solution of the transformed or effective $HT$ in a free rotor basis. Second, inclusion of the rotational terms from $HRO$ ($\propto$-independent). And third, inclusion of the terms from $HTR\prime$ including the $\propto$-dependent terms quadratic in the $P1$ and the small $\propto$-dependent terms from the residual Coriolis interaction. Results from the theoretical formulation and from numerical calculations for the above molecules will be presented.