DEPENDENCE OF 2-PHOTON IONIZATION PHOTOELECTRON-SPECTRA ON LASER COHERENCE BANDWIDTH

We have employed the technique of two-photon ionization via the transi ent intermediate S2 state of phenanthrene to obtain molecular photoele ctron spectra. This transient S2 electronic state is known to undergo internal conversion to a highly excited vibrational manifold of the S1 electronic state. Our observed photoelectron spectra show an interest ing dependence on the laser coherence bandwidth, which is interpreted in terms of changes in the degree of S1 and S2 contents of the superpo sition of molecular eigenstates which comprise the optically prepared intermediate state.