CHARACTERIZATION OF ASYMMETRY TRANSIENTS IN ROTATIONAL COHERENCE SPECTROSCOPY

The characteristics and origin of a new type of rotational coherence effect-asymmetry transients-are considered. Asymmetry transients are of two types, which we call C-type and A-type, respectively. C-type features are spaced by time intervals equal to 1/(4C). A-type features are spaced by time intervals equal to 1/(4A). Both types of transients can provide information on rotational constants that is not available from other types of rotational coherence effects. We show that the C-type transients arise from coherences between rotational eigenstates of the form J(tau) and (J + 2)tau -2 (in the J(tau) notation) and that the A-type ones arise from coherences between eigenstates J(tau) and (J + 2)tau + 2. The fact that such coherences produce asymmetry transients is shown to be a consequence of the limiting behavior of asymmetric top energy levels at high values of J. Experimental results in which asymmetry transients are present are reported for jet-cooled perylene, tryptamine (D conformer), 1-naphthol-water, and fluorene-benzene.