Characterization of Dissociation and Gas Heating in Femtosecond Laser Plasma with Planar Rayleigh Scattering and Rayleigh Scattering Polarimetry

摘要

Planar Rayleigh scattering and Rayleigh scattering polarimetry are used to characterize the dissociation kinetics, fluid dynamics and energy deposition in the afterglow of a femtosecond laser plasma, relevant for the FLEET (Femtosecond Laser Electronic Excitation Tagging) diagnostic technique. Fast heating is observed in the first 100ns, generating acoustic waves and a low density region with a corresponding temperature rise of at least ΔT = 330 ± 10 K. The energy deposition and temperature rise spatial profiles are observed to scale linearly with the emission intensity. Comparing this emission to the three-body recombination rate of nitrogen atoms shows that recombination processes can adequately explain the time history of the fluorescence after 1μs.