title: Photoelectron spectroscopy of pyrene anion clusters: autodetachment via excited states of anion and intermolecular interactions in anion clusters.
abstract: This study examined the anion clusters of pyrene (Py) by mass spectrometry, photoelectron spectroscopy, and theoretical calculations. The photoelectron spectra of Py(n)(-) (n=1-4) were obtained at various photon energies. A change in photodetachment wavelength resulted in a large change in the relative intensities of vibrational progression in the photoelectron spectra. It is proposed that the observed modulation of the Franck-Condon factors by the different photon energies reflects autodetachment via the excited states of anion. The photoelectron spectra of Py(n)(-) at 355 nm showed a broad band structure between the S(0) and T(1) states, which is also due to the autodetachment via a Feshbach resonance state. The photoelectron spectra of Py(2)(-) suggest the presence of a unique dimeric interaction between the two pyrene moieties, whereas the spectral features of Py(3)(-) are similar to those of Py(1)(-). The stable structures of Py(2)(-) and Py(3)(-) obtained by density functional theory calculations support the experimental findings, where different intermolecular interactions govern the stabilization of these two species.
authors.affiliation: School of Chemical and Biological Engineering, Seoul National University, Seoul 151-744, Korea.
authors.forename: Jeong Hyun
authors.initials: JH
authors.lastname: Kim
authors.forename: Sang Hak
authors.initials: SH
authors.lastname: Lee
authors.forename: Jae Kyu
authors.initials: JK
authors.lastname: Song