The sensitivity of photoelectric emission of polycrystalline aluminium
, produced by 248 nm laser pulses with p-polarization and 450 fs durat
ion, under incidence angles theta = 74-86 degrees, has been measured.
A nonlinear increase of photoemission efficiency, as a function of the
incident laser peak intensity in the range of 1-50 GW/cm(2), was disp
layed, which confirms earlier observations with gold and tungsten. Thi
s nonlinearity is consecutive to the non-thermal distribution of elect
ron gas of laser-heated metal on the time scale of the electron-phonon
relaxation time. Analysis of experimental data, using the model previ
ously developed by us [1], gives a value of electron-phonon relaxation
time approximate to 0.55 +/- O.11 ps.