We have studied the $K$-shell emission of an Al plasma which was generated by focusing a high contrast 150 fs laser pulse at a wavelength of 395 nm and intensity of $5\times {10}^{17}\mathrm{W}/{\mathrm{cm}}^2$ on a flat Al target tamped by a thin surface layer of MgO. The measured resonance lines ( ${\mathrm{Ly}}_{\alpha }$, ${\mathrm{He}}_{\alpha }$, and ${\mathrm{He}}_{\beta }$) and their Li-like and He-like satellites are extremely broadened and show a red polarization shift. Analysis of the ${\mathrm{Ly}}_{\alpha }$ and ${\mathrm{He}}_{\beta }$ satellites yields an electron temperature of $\approx 300\mathrm{eV}$ and an electron density of $(5–10)\times {10}^{23}{\mathrm{cm}}^{-3\mathrm{}}$.

• Received 23 October 1998

DOI:https://doi.org/10.1103/PhysRevLett.82.4843