Low-density plasma channels generated by femtosecond pulses

We present an investigation of the plasma channel formed along the trail of an intense femtosecond (fs) laser pulse propagating through helium, air and nitrogen at low pressures. The lifetime of the generated plasma channel of up to 60 μs was measured. We determined the electron-attachment mechanism as a dominant mechanism for the plasma relaxation. The initial electron densities, electron-attachment coefficients and plasma channel conductivity for different experimental conditions were obtained. PACS 52.50.Jm; 52.25.-b; 51.50.+v