Observation ofKL→LLx-ray satellites of aluminum in femtosecond laser-produced plasmas

The aluminum KL satellite emission spectrum excited by suprathermal electrons originating from the nonlinear interaction of a high intensity subpicosecond laser pulse with a solid target is obtained. The measured integrated intensity of the KL{→}LL satellites relative to the K{α} line is found to be 30% higher than in previous experiments performed with continuous, monoenergetic electron excitation. A double-vacancy creation by the shake-off process and a two step inner-shell ionization mechanism are investigated to interpret the data. An upper estimate of the preheating electron temperature is deduced from the analysis.