Experimental setup. The emission from the plasma was analyzed with an XUV spectrograph.
XUV spectra obtained from a carbon target. Black line: sub- laser pulses, gray line: laser pulses, plotted with an offset. For the sub- laser pulses, only the C and C lines are observed, whereas pressure ionization suppresses the higher series lines. For the longer laser pulses the whole hydrogen- and helium-like series including a recombination continuum are observed. [Figure reprinted with permission from Osterholz et al., Phys. Rev. Lett. 96, 085002 (2006). Copyright (2006) by the American Physical Society.]
XUV spectrum obtained from a boron nitride plasma generated by sub- laser pulses. Due to pressure ionization the higher series lines including the B are not observed in the spectrum. [Figure reprinted with permission from Osterholz et al., Phys. Rev. Lett. 96, 085002 (2006). Copyright (2006) by the American Physical Society.]
Solid lines: Ionization potential of hydrogen-like (a) and helium-like (b) boron in a boron nitride plasma versus density for three different temperatures. Dash-dotted lines: Excited state energy levels. At high density the higher levels do not exist anymore due to ionization potential depression. The density ranges which allow for the emission of the B but not the B lines are indicated for a temperature of .
Geometry for the simulation of the plasma expansion. The boundaries of the Lagrangian layers in the hydrodynamic simulations are denoted by . The initial position of the target surface is at .
Calculation of electron temperature (a), mass density (b), and electron density (c) in carbon plasma obtained with a one-dimensional Lagrangian hydrocode for different times. The time corresponds to the laser peak. The initial position of the target surface is at . The laser pulse with a peak intensity of and a duration of is incident from the left.
Computer simulation (MULTI-FS and FLY) of the XUV emission from carbon plasma. The and lines are clearly visible. The contributions of the higher series lines are strongly suppressed by pressure ionization.
Temporal evolution of the electron temperature and mass density of the Lagrangian layer number 92. The peak electron temperature is . The inset shows the temporal evolution of the intensities of the C (circles) and C (boxes) lines emitted by the layer.
Intensity ratios of the boron, carbon, and nitrogen resonance lines observed in the experiment (boxes) and obtained from computer simulations (circles).
Intensity ratios of the boron resonance lines versus laser intensity. Boxes: experiment, line: computer simulation (MULTI-FS and FLY)
shell spectrum obtained from a Ti target irradiated with the sub- laser pulses. Black line: experiment, red line: computer simulation. The labels of the transition are explained in Table I.
List of transitions from shell excited levels contributing to the XUV emission of the titanium plasma.
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