Pulse duration effect on the distribution of energetic particles produced by intense femtosecond laser pulses irradiating solids

Abstract

The energy distribution of hot electrons produced by a very short, intense laser pulse (I=2/4×1018 W/cm2, 60 fs, λ=800 nm, obliquely incident p polarized) is investigated theoretically via particle simulation and experimentally via measurements of the electron distribution in the MeV region and the Doppler-shifted emission spectrum of fast ions. This energy distribution is shown to be greatly different from the known two-temperature distribution. The hot electrons with energies near the maximal (∼2 MeV) constitute the distribution with an effective temperature Th considerably higher than that of lower-energy electrons, which dominate the emission of energetic ions. The temperature scaling with the laser intensity differs from the known Th∼I1/2.