Simultaneous observation of dipole-bound and valence electron states in pyridine tetramer anion

Coexistence of dipole-bound and valence electron states was observed by photoelectron spectroscopy in pyridine tetramer anion despite the fact that pyridine itself does not bind electrons by either mechanism. The photoelectron yield for the two states showed distinctly different laser polarization dependence. The fact that these two states have rather disparate thermodynamic stabilities suggests that there may exist an energy barrier separating the two forms in configuration space of the cluster. (C) 1998 American Institute of Physics. [S0021-9606(98)02446-5].