Semiclassical description of purely rotational recurrences for collisionless asymmetric top molecules: new results Original Research Article

A semiclassical approach, based on the discrete WKB approximation, is developed for the description of purely rotational recurrences in thermal ensembles of collisionless asymmetric top molecules. Exact non-perturbative expressions are derived for the periods of the J-, H-, and K-type transients. These formulas automatically account for the phenomenon of increasing the period of the J-type transients for oblate asymmetric tops and decreasing that for prolate asymmetric tops in parallel with the enhancement of molecular asymmetry. The asymmetry corrections are demonstrated to magnify the period of the K- and H-type transients, irrespective of the form of the molecular top. The polarity of the A- and C-type transients is established. New kinds of transients are predicted and characterized by their periods and polarity. The most important of these is demonstrated to be the P-type transients arising for planar molecules.