OPTICAL PROBING OF HOT EXPANDED STATES PRODUCED BY SHOCK RELEASE

The angle and polarization dependence of optical emission and reflecti on from dense aluminum plasmas produced in the release wave of a stron g shock is investigated theoretically. It is shown that with high-spee d measurements (few-picosecond resolution), optical probing of the unl oading plasma can be used to examine transport properties and ionizati on balance of thermodynamic states in the vicinity of the liquid-vapor critical point. The calculations were performed using data from two w ide-ranging theoretical models of plasma conductivity, a semianalytica l model due to Lee and More [Phys. Fluids 27, 1273 (1984)] and a parti al-wave analysis due to Rinker [Phys. Rev. B 31, 4207 (1985); 31, 4220 (1985)]. The models predict substantially different values for the co nductivity close to the liquid-vapor critical point (more than a facto r of 10 for the electron-ion collison time); the different results obt ained for the two models sugest that experimental measurements could p rovide new information for improving the current understanding of dens e plasma properties.