Temporally resolved properties of femtosecond laser-induced plasmas in air

We present the temporally resolved measurements of electron number density and temperature over timescales on the order of 1 ns to 10 ns in a femtosecond (fs) laser-induced plasma (LIP). Additionally, we also report on the neutral gas number density and rotational temperature over timescales on the order of 1 ns to 1000 ns. The fs LIP was generated in ambient air and investigated using laser Thomson and rotational Raman scattering. Electron number densities were observed to decrease from   at early times to   at later times, while the electron temperature remained within  eV throughout the probed range. The neutral gas number density remained nearly constant at   for the first 50 ns before declining to   after 500 ns. The rotational temperature initially decreased from  K within the first 30 ns to  K at 100 ns, before rising back to  K. Finally, the experimental results were compared with simulations, showing good agreement.