  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.
