Measurement of energetic electrons from atomic clusters irradiated by intense femtosecond laser pulses

Spectra of energetic electrons in the 100 keV range were measured from the interaction of intense femtosecond laser pulses with clusters of xenon or argon. The interaction of 28 fs pulses with cluster targets revealed quite different results with respect to applied laser intensity. At the laser intensity of 1x1016 W/cm2, the absorption by xenon clusters was about 25%; however, at the laser intensity of 1x1017 W/cm2, the laser energy absorption drastically increased to 78%, and the efficient coupling between the laser pulse and cluster target produced electrons with energy as high as 500 keV. The estimated hot electron temperatures ranged from about 30 to 90 keV depending on atoms and backing pressures