Ethylene and ethylene oxide react readily with silver clusters at 70 K to form the addition complexes, Ag-n(C2H4), and Ag-n(C2H4O)(m), respectively. The infrared photodissociation spectra of Ag-n(C2H4)(m) and Ag-n(C2D4)(m) (n = 3-7) recorded in the 9-11 mu m region show several characteristic vibrational bands of ethylene lying near their gas phase frequencies. Photoionization spectroscopy studies reveal that the ionization potentials (IPs) of the complexes decrease monotonically with adsorption of additional ethylene molecules. Together, these results imply that as on macroscopic Silver surfaces, ethylene adsorbs molecularly to small silver clusters, with a net donation of electron density into the underlying cluster. Similarly, silver cluster-ethylene oxide complexes display IPs that decrease with increasing adsorbate coverage. The infrared depletion spectra of Ag-n(C2D4O)(m) complexes reveal a single feature at 949 cm(-1), assigned to the nu(4)(a(1)) fundamental of C2D4O. These results verify that ethylene oxide adsorbs molecularly to silver clusters, with the oxygen atom oriented toward the silver cluster. (C) 1997 American Institute of Physics.