Enhanced K-shell x-ray line emissions from aluminum plasma created by a pair of femtosecond laser pulses

The influence of an ultrashort prepulse on K-shell x-ray line emissions fro m Al plasma produced by 100 fs Ti:sapphire laser pulses is studied. By intr oducing an independent 100 fs prepulse, a more than 20-fold enhancement in K-shell emission was achieved. We could experimentally optimize K-alpha and He-alpha line emissions. In case of oblique incidence, resonance absorptio n made it possible to maximize K-alpha emission while keeping pulse duratio n short. On the other hand, He-alpha line emission was maximized when a sep aration between two laser pulses was large, resulting in pulse broadening ( similar to 30 ps). (C) 2001 American Institute of Physics.