TIME-RESOLVED AND SPACE-RESOLVED OBSERVATION OF POPULATION INVERSION IN A HE-LIKE AL PLASMA PUMPED BY FUNDAMENTAL AND 2ND-HARMONIC PULSES OF A ND-GLASS LASER

Time- and space-resolved spectra of laser-produced aluminum plasma are observed with a framing crystal x-ray spectrometer. A massive slab Al target is irradiated by the fundamental or second-harmonic laser puls e from a Nd:glass system at a peak intensity of 8.5 +/- 0.9 x 10(14) W /cm(2). Population inversion are observed between the 4 and 3 levels o f He-like Al for fundamental pumps and also between the 3 and 2 levels for the second harmonics. The origin of the 3-2 inversion can be attr ibuted to the higher initial electron density of the plasma produced b y the second-harmonic pump. A discussion of reabsorption effects of th e resonance line is given. (C) 1996 Optical Society of America