Optical probing of hot expanded states produced by shock release

The angle and polarization dependence of optical emission and reflection from dense aluminum plasmas produced in the release wave of a strong shock is investigated theoretically. It is shown that with high-speed measurements (few-picosecond resolution), optical probing of the unloading plasma can be used to examine transport properties and ionization balance of thermodynamic states in the vicinity of the liquid-vapor critical point. The calculations were performed using data from two wide-ranging theoretical models of plasma conductivity, a semianalytical model due to Lee and More [Phys. Fluids 27, 1273 (1984)] and a partial-wave analysis due to Rinker [Phys. Rev. B 31, 4207 (1985); 31, 4220 (1985)]. The models predict substantially different values for the conductivity close to the liquid-vapor critical point (more than a factor of 10 for the electron-ion collison time); the different results obtained for the two models suggest that experimental measurements could provide new information for improving the current understanding of dense plasma properties