The single-photon zero kinetic energy (ZEKE) photoelectron spectrum of the copper-pyridine 1:1 complex has been observed in order to investigate the vibrational structure of the corresponding ion. The adiabatic ionization potential of the complex was measured to be 5.418 eV and the Cu-N stretching frequencies of the neutral and ionized complex were determined to be 195 and 275 cm(-1), respectively. (C) 2004 Elsevier B.V. All rights reserved.