Size-dependent hot-electron dynamics in small Pd-n(-)-clusters

Using time-resolved photoelectron spectroscopy we show that electron relaxa tion processes via inelastic electron-electron scattering are efficient ene rgy dissipation channels not only in bulk metals but also in extremely smal l transition metal clusters. The photoelectron spectra of optically excited Pd-3(-), Pd-4(-), and Pd-7(-) reveal effective electron relaxation times o f less than 100 fs. Moreover the relaxation times vary with cluster size. I n comparison to simple metal clusters the bulklike inelastic scattering rat es in open d-shell transition metal clusters are attributed to the larger v alence electron level density. An energy transfer to the vibrational degree s of freedom occurs within 10 ps. (C) 2001 American Institute of Physics.