Ionization Model to Estimate the Density and Temperature Offs-Laser-Induced Plasmas in Air

We present a simple ionization model to assess the density of plasmas created in air by ionization induced by the electric field of ultrashort laser pulses. It calculates the average ionization induced by the laser taking into account the known threshold intensities for each ionic state, the beam spatial profile and the atmospheric composition, estimating the plasma density. The model density predictions are compared to experimental results obtained by a time-resolved Mach-Zehnder-like interferometer, and are also used as entry parameters to evaluate the plasma temperature by the Saha equation.