Theoretical and experimental studies of laser-produced plasmas driven by high-intensity femtosecond laser pulses

A theoretical and experimental study of the dynamics of the electron density gradient in near-solid-density plasmas produced by the interaction of ultra-short laser pulses with solid targets at intensities between ${10}^{13}$ and ${10}^{16}$ ${\mathrm{W/cm}}^{\mathrm{2}}$ and pulse duration between $\text{0.12}$ and $\text{2.5}$ ps is presented. X-ray spectroscopy of $\text{n=3}$ to $\text{n=1}$ resonance and dielectronic satellite lines is used to determine the range of electron densities in the plasma. Frequency-domain interferometry is employed to measure the expansion velocity and the electron density gradient scale length as a function of laser pulse duration and intensity. Quantitative agreement is noticed with one-dimensional hydrodynamic simulations which include the solution of the wave equation for the laser field.