Effect of losses due to the residual electron energy on the temporal profile of a femtosecond ionizing laser pulse

A study is made of the combined action of the losses associated with overco ming the ionization potential barrier and those associated with the residua l energy acquired by the electrons on a laser pulse propagating in a gas an d ionizing it. It is shown that, depending on the laser and gas parameters, the losses due to overcoming the ionization potential barrier may be eithe r larger or smaller than those associated with the residual electron energy . However, for pulses that penetrate sufficiently deeply into the gas, the residual energy-related losses are always larger than the ionization potent ial-related losses because of the steepening of the laser pulse profile dur ing ionization. (C) 2000 MAIK "Nauka/lnterperiodica".