An effect of potential shallowing and the determination of barriers to internal rotation (in electron diffraction)

A relationship between the molecular potential ofinternal rotation and its substitute (a parabola), shallowed in the surrounding of the energy minimum, as determined from the fitting of electron diffraction data, is pointed out by the principle of maximum similarity. The numerical approach introduced allows to determine the barrier of internal rotation from the scaling factor of the parabola as well as from average torsional angles related to it. The scaling factor itself is shown to be a lower boundary of the rotational barrier. (AIP)