Direct measurement of electron numbers created at infrared laser-induced ionization of various gases

Abstract

In this work, we present temporally resolved measurements of electron numbers created at photoionization of various gases by femtosecond laser pulse at 800 nm wavelength. The experiments were conducted in $O_2$, $Xe$, $Ar$, $N_2$, $Kr$ and $CO$ at room temperature and atmospheric pressure. Elastic microwave scattering was used to directly measure the electron numbers. Numbers of electrons in the range $3*10^8$ to $3*10^{12}$ electrons were produced by the laser pulse energies 100-700 uJ. After the laser pulse, plasma decayed on the time scale varied from 1 to 40 ns depending on the gas type and governed by two competing processes, namely, the creation of new electrons from ionization of the metastable atoms and loss of the electrons due to dissociative recombination and attachment to oxygen.