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This letter reports the experimental evidence of a 2.3 eV blue shift of the plasmon loss lines observed in the x-ray photoelectron spectra of an ultrathin Si layer equivalent to 1.5×1015  at./cm2 deposited onto a randomly oriented Al2O3 single crystal. The plasmon line shifts, which is roughly proportional to the deposited Si(mass)−2/3, are attributed to quantum confinement effects in agreement with electron energy loss measurements performed on nanosized Si particles.

The experimental results of multiphoton electron emission from Cu and W induced by 2-eV 100-fs laser pulses with s and p polarizations at incidence angles between 0°and 85°and different intensities are reported. The data show a third-order nonlinear photoemission process for Cu and a fourth-order behavior for W. For both metals the electron emission is higher for the polarization in the incidence plane, with a maximum value at the pseudo-Brewster angle, while the electron yield as a function of the incidence angle exhibits an unambiguous dependence on the bulk absorption coefficient and it can be accounted for on the basis of the Fresnel equations. ͓S0163-1829͑96͒02233-3͔ PHYSICAL REVIEW B