Collective absorption of intense laser pulses by atomic clusters is
studied by PIC simulations. The cluster is modeled in two-dimensional
calculations as a cylindrical plasma column with a diameter of
D = 6.4 nm and an initial electron density of
ne0 = 1023
cm−3. The frequency and intensity dependence of
absorption is discussed. It is found that nonresonant absorption by
electron emission increases as a power law with the laser intensity.
The absorbed energy per electron reaches a maximum of about
Wmax =
mωp2D2
(ωp: plasma frequency, m: electron
mass) at the intensity where ionization saturates.