Short-Time Electron Dynamics in Aluminum Excited by Femtosecond Extreme Ultraviolet Radiation

Abstract

The femtosecond dynamics of the electrons in aluminum after an intense extreme ultraviolet pulse is investigated by Monte Carlo simulations. Transient distributions of the conduction band electrons show an almost thermalized, low-energy part and a high-energy tail. Constructing emission spectra from these data, we find excellent agreement with measurements. The radiative decay mainly reflects the colder part of the distribution, whereas the highly excited electrons dominate the bremsstrahlung spectrum. For the latter, we also find good agreement between predicted and measured energy scales.

Nonthermal graphitization of diamond induced by a femtosecond x-ray laser pulse

“…The Monte Carlo (MC) method is used to describe photoabsorption and Auger decays of K-shell holes, as well as the transient nonequilibrium kinetics of high-energy electrons and their secondary cascading. 11,33,35,36,38 A temperature equation is applied to describe low-energy electrons, which reach (nearly) thermal equilibrium already during the first few femtoseconds after the beginning of the laser pulse, following the "bump-on-hot-tail" distribution. 11,33,[44][45][46] The high-energy-electron and the low-energy-electron domains are interconnected, as electrons can gain or lose energy and go from one domain to another.…”

“…The fourth-generation light sources, the free-electron lasers (FEL), such as FLASH, 1 LCLS, 2 SACLA, 3 and FERMI, 4 stimulate rapid advances in many scientific fields, including investigation of atoms, 5,6 molecules, 7,8 clusters, 9,10 and solids [11][12][13] exposed to intense laser fields. It enables creating and probing plasmas, 14,15 hot dense matter, [15][16][17] and warm dense matter, 18,19 as well as the investigation of the interaction of low-fluence ultrafast laser pulses with matter, with applications to structural studies within solidstate physics, 11,[20][21][22][23] nanophysics, 24 molecular physics, and biophysics.…”

“…11,32,33 First, the photoabsorption promotes electrons from the bound states of the valence band or deep atomic shells (K shell for carbon) to the conduction band. This process occurs during the action of the laser pulse.…”

“…It enables creating and probing plasmas, 14,15 hot dense matter, [15][16][17] and warm dense matter, 18,19 as well as the investigation of the interaction of low-fluence ultrafast laser pulses with matter, with applications to structural studies within solidstate physics, 11,[20][21][22][23] nanophysics, 24 molecular physics, and biophysics. 25 The presently operating free-electron lasers can produce laser pulses with durations of a few tens down to a few femtoseconds.…”

X-ray free-electron laser studies of dense plasmas

“…Performed at a photon energy of 92 eV, the intense 15 fs pulse saturated the L-shell absorption channel, leading to a large increase in the transmitted signal, and an energy deposition gradient between the front and rear of the target foil that was deduced to be linear rather than exponential. Spectroscopy was used to deduce heating to a temperature of a few eV during the FEL pulse (Vinko et al 2010), and at later times the sample was estimated to have thermalized to around 20 eV, sufficient to create a warm-dense Al plasma (Medvedev et al 2011). Saturable absorption has since been observed in a range of systems in the XUV (Yoneda et al 2009;Inubushi et al 2010;Di Cicco et al 2014).…”