Stability patterns of multiphoton ionized YAun clusters

Binary YmAun metal clusters (m less than or equal to 5, n less than or equa l to 65) are produced by a laser vaporization source. The clusters are ioni zed and excited by multiphoton absorption (E-hv = 6.4 eV) and mass abundanc e spectra were taken by time-of-flight mass spectrometry. The mass spectra of the YAun ions reveal distinct intensity steps at n = 2, 6, 16, 32, and 5 6 which correspond for n > 2 to the well known electronic shell model, prov ided that the yttrium atom contributes three free electrons to the metallic binding of the gold clusters.