Momentum transfer to laser-irradiated targets, indicating the nonlinear interaction force

Measurements by Metz of the momentum ρ transferred to laser‐irradiated targets are evaluated and compared with the results of the nonlinear force of laser‐plasma interaction. The measured thresholds for the intensity I*, estimated to be 2 × 10¹⁴ W/cm², agree with the threshold of the nonlinear force. The measured highly superlinear relation P ≈ I⁴ agrees very well with the theory for not too large intensities $\mathrm{I\gtrsim \; I*}$ . A consequence would be an electron energy of coherent oscillation near 10⁴ eV, which may cause a nonthermal origin of fusion neutrons in other experiments.