Knowledge Bank

Previous $experiments1$ have shown interesting, mode selective vibrational predissoctation from each of seven inftial vibrational levels in the $S1$ state of the complex. As an example. V. P. after excitation of the $\xi 1$ complex occurs by two major channels producing the pDFB monomer in the $61$ and $0\circ$ states. These monomer states have been recognized by their distinctive vibrational structure in dispersed fluorescence. Now we are using improved fluorescence resolution to learn about the initial rotational distributions in these monomer states, as revealed by rotational band contours. Rotational contours of the $611$ and $000$ transitions differ from each other markedly: with the $611$ transition having a broader contour. Neither contour matches those calculated for thermal rotational distributions, and that of the $000$ band differs most from an equilibrium contour. Nonetheless, if both were to be described by temperatures, we would say that these monomers are relatively cold. The $61$ monomer is between 30-40 K and the $O\circ$ monoser is perhaps closer to 20 K. The complex from which the V. P. occurred was at 5 K when it was laser excited