Plasma generation in air by intense laser pulses with various pulse durations

We have studied the plasma generation through collecting the charged particles produced in laser-induced breakdown in atmospheric air. This breakdown is produced by ultrashort laser pulses with various durations ranging from 200 fs to 2 ps at a fixed pulse energy of 8 mJ. We found that the plasma yield increases first with the increment of pulse duration and then: reaches a plateau at a duration longer than 500 fs The generated plasma temperature is estimated to be higher than 5 x 10(5) K.