Figure 4

Signature of ponderomotive force.

Angular distribution and energy spectra measurements of fast electrons for ‘p’ polarized light at intensity of 2 × 10¹⁹ W cm⁻². (a) The angular distribution of fast electrons recorded in the image plate. SP: specular, TS: target surface; J × B: laser axis, RN: rear normal. (b) Polar plot of the electron flux. The black arrow and grey slab indicates laser direction and target orientation, respectively. (c) Energy spectra of fast electrons measured along the J × B direction. T₁ and T₂ indicate the fitted temperature of fast electrons. (d) Intensity dependent peak of the emitted second harmonic for ‘s’ polarized light. The estimated velocity of the critical surface estimated from the Doppler shift is also shown in the same figure. The dotted horizontal line is the location of second harmonic peak estimated from the spectra of the fundamental laser pulse.