Spatiotemporal evolution of laser-induced plasmas in air: Influence of pressure

In this paper, we focused on the influence of gas pressure on the dynamic characteristics of laser-induced plasma (LIP) in air. The energy-dependent transmittances of a 1064 nm laser to LIPs generated at the pressure of 0.2-5 atm were measured. Laser Rayleigh scattering and Thomson scattering methods were applied to investigate the evolution of laser-produced shock wave and radial distribution of electron number density (n(e)) and electron temperature (T-e) of LIP in air. The fraction of the shock wave energy to the total laser energy absorbed is about 40%-52% and increases upon increasing pressure. The higher the gas pressure, the greater n(e) and T-e within the central of LIP and a faster decaying rate of T-e and n(e). The electron number density decays exponentially with time, and the decay index is between -0.891 and -1.177. A torus structure in LIPs is generated during the later stage of plasma decay and significantly affects the distribution of T-e, n(e) and the intensity of plasma emission.

Automated summary

This study focuses on the influence of gas pressure on the dynamic characteristics of laser-induced plasma, revealing that higher gas pressure leads to greater electron number density and electron temperature within the central of LIP and a faster decay rate. A torus structure in LIPs is generated during the later stage of plasma decay, significantly affecting the distribution of electron number density, electron temperature, and the intensity of plasma emission.