Electron densities, temperatures, and the dielectric function of femtosecond-laser-produced plasmas

The optical properties of dense plasmas in the extreme ultraviolet spectral range are investigated experimentally and theoretically. A method is prese nted that enables measurement of electron densities in excess of 10(24) cm( -3). High-order harmonics are transmitted through a femtosecond-laser-produ ced plasma probing the optical density at several wavelengths. This techniq ue has the advantage of providing direct access to ultrahigh electron densi ties, and achieves a precision of about 20% at zero time delay. The dielect ric function of a dense carbon plasma was calculated including effects of h igher density and the contribution of bound electrons. [S1063-651X(99)05703 -7].