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We report on the observation of a new and very effective mechanism of interlayer mass transport which bypasses the Schwoebel-Ehrlich barrier for the diffusion of atoms over step edges. The channel for a rapid mass transport opens when a two-dimensional island engaged in a random walk on a surface touches the boundary of a descending step. The decay rate of the island then increases by about 2 orders of magnitude. Even entire mounds can disappear in a very short time due to ledge contact events caused by equilibrium fluctuations of step edges. [S0031-9007(97)

Photoelectron spectra of small mass-separated W n clusters cooled in a seeding gas are recorded with a low laser flux that ensures single-photon events. The spectra exhibit (i) sharp features due to direct photoemission and (ii) a broad emission signal whose intensity decreases with increasing kinetic energy. The latter is caused by delayed electron emission, a process similar to bulk 'thermionic emission'. The kinetic energy distribution of these electrons can be approximated by a Boltzmann function with a temperature corresponding to the photon energy divided by the number of vibrational degrees of freedom of the cluster.

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