15min:

JASON F. FULLER, BRAD R. SOHNLEIN AND DONG-SHENG YANG, Department of Chemistry, University of Kentucky, Lexington, KY 40506-0055.

Gas-phase complexes of scandium with pyrene (C₁₆H₂₀) and naphthalene (C₁₀H₈) are produced by using laser ablation and a polycyclic aromatic hydrocarbon (PAH) oven in a pulsed molecular beam source. The resulting Sc-PAH complexes are characterized with pulsed field ionization-zero electron kinetic energy (PFI-ZEKE) photoelectron spectroscopy. The PFI-ZEKE spectrum of Sc-Pyrene exhibits vibrational progressions of 361 and 154 cm^-1 and a vibrational spacing of 144 cm^-1, with the band origin at 40937 cm^-1. Through comparison with ab initio and Franck-Condon factor calculations, it is determined that this spectral profile arises from a Sc-pyrene complex in which the scandium atom is bound to the ``outer'' ring in an <sup>4</sup>- configuration. The 361 cm<sup>-1</sup> progression is assigned to the Sc<sup>+</sup>-ring stretch and 154 and 144 cm<sup>-1</sup> features are assigned to pyrene ``flying'' modes in the cation and neutral, respectively. For Sc-naphthalene, the spectrum shows four vibrational intervals of 389, 347, 298 and 112 cm^-1, with the adiabatic ionization energy of 41192 cm^-1. A preliminary analysis indicated the Sc atom is in an ² bonding mode in this complex. However, a detailed analysis is still in progress.