OBSERVATION AND DESCRIPTION OF A NEW TYPE OF TRANSIENT IN ROTATIONAL COHERENCE SPECTROSCOPY

We report the observation and explanation of a new type of rotational coherence effect that can occur in experiments on species having transition dipole vectors that deviate from the directions of their principal rotation axes. These newly observed transients arise due to the relaxed rotational selection rules in such species and occur at times almost proportional to 1/2[A′ - 1/2(B′+ C′)]-1. With the additional information available from such transients all three excited-state rotational constants of a species can be obtained. This point is illustrated for conformers of 3-indolepropionic acid and for tryptamine-water complexes. © 1990 American Chemical Society.