Abstract
The abnormal torsional splittings in the S 1 state of acetaldehyde, induced by the aldehyde inversion motion, was analyzed. The torsional splittings were explained by the G 6 group-theoretical high-barrier formalism. The modification in the formalism allowed its application to the reduced molecular symmetry G 6 on mono-N-deuterated methylamine. Methyl torsional tunneling, aldehyde-hydrogen inversion tunneling and overall rotation received treatment from the formalism. The formalism was effective in fitting the partially anomalous K-doublet structure of the S 1 state. Partially anomalous K-doublet structure was originated from coupling of torsion and rotation motion with the aldehyde-hydrogen inversion.