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.
