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were observed by stimulated Raman-UV double resonance spectroscopy. Cluster structures were determined on the basis of the observed vibrational spectra, rotational contour analyses of the high resolution S 1 -S 0 electronic spectra and ab initio molecular orbital calculations with the HF/6-31G(d,p) basis set. It was found that the types of the cluster structures are classified into three groups. (1) The clusters with H 2 O, CH 3 OH and CH 3 CN represent the 'side'-type structure, in which the intermolecular bond is formed in the phenyl plane of benzonitrile, and the benzonitrile dimer also belongs to this structure. (2) The clusters with Ar and CCl 4 form the 'on-top'-type structure, where Ar or CCl 4 is located above the phenyl plane. (3) The clusters with CHCl 3 and CHF 3 have the 'linear'type structure, in which these molecules are located at the N end of the CN group of benzonitrile. The rate constants of the vibrational relaxation for these clusters occurring after the Raman excitation to their n 12 vibrations were also observed. It was found that different rate constants are associated with the different types of cluster structures. That is, the 12 1 levels of the 'side'-type clusters relax much faster than those of other types of the clusters. The results represent a clear indication that the anharmonic coupling between n 12 and intermolecular vibrations are much larger in the 'side'-type clusters than others.

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Dispersions of image potential states on a graphite surface (denoted IPS1) and on 1 monolayer (ML) film (denoted IPS2) of lead phthalocyanine (PbPc) are investigated by the micro-spot angle-resolved two-photon photoemission (micro-AR-2PPE) spectroscopy. On the graphite surface, whole dispersions of the two members of IPS1 (n = 1 and 2) are observed. The n = 1 IPS1 peak is weakly visible at energy higher than the vacuum level. The effective mass of an electron in the n = 1 IPS1 becomes slightly light at the high momentum region, suggesting the interaction between the IPS1 and the unoccupied σ-band of graphite. On the PbPc film, the IPS2 band forms a band gap and back-folds at the boundary of the Brillouin zone. A 1-dimensional Kronig-Penny model is used to reproduce the effective mass and the shift of binding energy.

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