HIGH-RESOLUTION X-RAY-SPECTRUM OF A LASER-PRODUCED BARIUM PLASMA IN THE 9.10-9.36-ANGSTROM WAVELENGTH RANGE

A highly stripped barium plasma is produced by 120-fs laser pulses irr adiating a BaF2 target. The spectrum emitted by the plasma in the 9.10 -9.36-Angstrom wavelength range is recorded using a high-resolution sp herically bent mica crystal. On the basis of the HULLAC atomic code, a level-by-level collisional-radiative model including autoionization a nd dielectronic capture processes is developed to calculate the wavele ngths and intensities of the spectral lines emitted by each of the Cu- , Zn-, and Ga-Like barium ions. 3d-nf (n = 6,7) spectral lines with di fferent spectator electrons, previously observed only as unresolved tr ansition arrays, are resolved. The theoretical results agree reasonabl y well with experiment. Best agreement is obtained for electron densit y and temperature of 5x10(21) cm(-3) and 120 eV, respectively. The int ensity ratios of the resolved Cu-like barium lines an shown to be usef ul tools for electron density and temperature diagnosis. This diagnost ic method was not possible with low-resolution spectroscopy. It is fou nd that at relatively low temperature and high density as in the prese nt experiment, the relative intensities of lines within each ionizatio n state are independent of the ion density ratio of adjacent ionizatio n states.