The adsorption and dissociation of (C2H5)(2)Zn was studied on Pd(100) surface. The methods used included photoelectron spectroscopy (XPS, UPS), electron energy loss spectroscopy (EELS) in the electronic range, temperature-programmed desorption (TPD), and work function measurements. Diethyl zinc adsorbs predominantly irreversibly on Pd surface. At submonolayer it dissociates even at 90 K. Thermal dissociation of adsorbed monolayer occurs at 170-230 K. Illumination of molecularly adsorbed layer at 90-95 K enhances the extent of the dissociation. The primary products of the thermal and photodissociation, C2H5 and Zn, were characterized by a C(1s) binding of 284.0 eV and by Zn(2p(3/2)) binding energy of 1021.0 eV. The C2H5 reacted to form C2H4 and C2H6. Coupling reactions to C4H10 and C4H8 were also observed. On the basis of He I, He II, and EELS data, energy levels of electron orbitals for (C2H5)(2)Zn-Pd(100) system have been calculated.