Hot electron effects on the satellite spectrum of laser-produced plasmas

In laser-produced plasmas, the interaction of the intense laser light with plasma electrons can produce high-energy superthermal electrons with energi es in the keV range. These hot electrons can influence the level population s which determine spectral line structure. In the present paper, the effect of hot electrons on the X-ray satellite spectrum of laser-produced plasmas is studied. Calculated spectra are compared with experimental observations . Magnesium targets irradiated by three different types of laser pulses are considered. These include, a high-intensity 600 fs Nd-glass laser, a 1 ns Nd-glass laser, and a 2 ns CO2 laser. The Nd-glass laser experiments were c onducted recently at the Los Alamos Trident Facility and the CO2 data were recorded by MISDC. High-resolution spectra were measured near the He-like r esonance line of magnesium. The calculations employ an electron energy dist ribution which includes a thermal and a hot electron component, as part of a detailed collisional-radiative model. Plasma parameters including electro n temperature, density, and hot electron fraction are estimated by choosing best fits to the experimental measurements. The calculations show that hot electrons can cause several anomalous effects. The Li-like jkl, abcd, and qr satellites can show intensities which are generally attributed to electr on densities in excess of 10(23) cm(-3). In addition, the relative amplitud e of the intercombination line can be unusually large even at high electron densities due to enhanced collisional excitation of the ls2p(3)P state by hot electrons. (C) 1999 Elsevier Science Ltd. All rights reserved.