Spectroscopic signature of non-Maxwellian and nonstationary effects in plasmas heated by intense, ultrashort laser pulses

The interaction of an intense (${10}^{16}$ W/${\mathrm{cm}}^2$), ultrashort (400 fs) 1.06 μm laser pulse normally incident on an aluminum preformed plasma was simulated with an electron kinetic code. Postprocessing with a detailed atomic model predicted the resulting K-shell x-ray spectrum. Both the very rapid time variation and the non-Maxwellian energy distribution (due to the steep gradients, energetic electrons stream from the hot into the cold plasma and enhance the excitation of Li-like satellite there) greatly modify the line ratios, even without any addition of hot electrons.