Electronic continua in time-resolved photoelectron spectroscopy. II. Corresponding ionization correlations

We investigate further the role of ion electronic continua in time-resolved photoelectron spectroscopic measurements of ultrafast nonadiabatic couplin g. In the preceding paper [Blanchet, Zgierski, and Stolow, J. Chem. Phys. 1 14, 1194 (2000)], the limiting case of complementary ionization correlation s permitted a disentangling of electronic from vibrational dynamics. Here w e examine the other limiting case in which the nonadiabatically coupled sat es (e.g., S-2 and S-1) correlations correspond to the same ionic continua, presumably an unfavorable case. We use ultrafast internal conversion in the polyaromatic hydrocarbons phenanthrene and naphthalene as examples. In thi s situation, the geometry changes (displacements) upon nonadiabatic crossin g and upon ionization will strongly affect the ability to disentangle elect ronic from vibrational dynamics. Particularly, phenanthrene and naphthalene are both very rigid molecules and have small displacements upon internal c onversion and ionization, still allowing for direct monitoring of the S-2 s tate internal conversion rate. (C) 2001 American Institute of Physics.