Soft x-ray spectra of highly ionized elements with atomic numbers ranging from 57 to 82 produced by compact lasers

X-ray emission spectra in the spectral range of 2-13 nm from 19 kinds of material with high atomic numbers (lanthanum through lead) were recorded with a grazing incidence spectrometer equipped with a microchannel plate detector. There is an intense, narrow spectral band in these spectra which shifts toward shorter wavelength and becomes weak in intensity with increasing atomic number. The materials were irradiated either by a 4 J/35 ns slab Nd:glass laser or by a 0.5 J/8 ns Nd:YAG laser. The absolute photon intensities of the spectra were determined with an absolutely calibrated charge coupled device camera. The peak spectral brightness of the emission at the peak intensity of the spectral band for lanthanum plasma was estimated to be 2.1×10¹⁶ photons/s/mm²/mrad² in 0.1% bandwidth. The origin of the narrow, intense spectral bands in the recorded spectra and their dependence on target materials and laser wavelength are interpreted.