The many-particle quantum dynamics of the electron gas of thin metal films
subject to intense visible and infrared laser irradiation is simulated. It
is shown that the laser interaction with the metal electron gas leads to a
coherent emission of photons in the ultraviolet region with an energy corre
sponding to the plasma frequency wp of the metal electron gas. A redshift o
f the emitted radiation with respect to omega(p) can be attributed to the d
ecreasing density of the metal electron gas near the surface of the film. W
e also discuss results obtained by classical particle-in-cell simulations t
o compare the predictions of our quantum mechanical approach with those of
another approach.