The time-independent ion distributions of variable composition laser-produced Sn plasmas are studied for a wide range of electron temperatures and atomic number densities, the purpose of which is to elucidate the effect that varying the number density of Sn within a mixed species plasma has upon the steady state populations of Sn and its ions. Particular emphasis will be placed on binary mixtures of Sn with Li, C, O or Sm and more specifically the charge states Sn8+ to Sn13+ within these mixed plasmas, where it will be assumed that the plasma is optically thin. It is found that using these composites has relatively little effect upon the Sn ion population distributions for plasma atomic number densities of less than approximately 1019.5 cm−3. However, for greater values of number densities the Sn ion populations can be shifted by as much as 10–15 eV for Li mixtures. These results are of particular relevance to current research being carried out on extreme ultraviolet lithographic technologies for the optimization of XUV sources in the 13.5 nm wavelength region, which include composite target investigations.

The aim of this study is to investigate ways to maximise the efficiency of tin based laser produced plasmas as sources of EUV radiation in the 2% band centered on 13.5 nm. It has been found that targets containing below 15% tin atoms by number emit more brightly in the spectral region around 13.5 nm than pure tin targets. Furthermore, if the remaining material in the target is composed on primarily low-Z atoms, then both plasma continuum radiation and Bremsstrahlung radiation are greatly reduced. In addition, if the target is illuminated with a prepulse, the conversion efficiency shows a distinct increase. The third parameter under examination is the laser power density, which controls the ion distribution in the plasma. The influence of low-Z atoms on the tin ion distribution in the plasma has been investigated and found to be of little consequence. Measurements were made in the region from 9 -17 nm on an absolutely calibrated 0.25-m flat field grazing incidence spectrograph, and on two 2-m grazing incidence spectrographs. Spectra and conversion efficiency data from a range of target materials and illumination regimes are presented.

The extreme ultraviolet photoabsorption spectra of cerium from five to nine times ionized have been recorded in the 70–120 eV region using the dual laser plasma technique. These represent the highest ion stages observed to date using this method. The spectra below 115 eV were found to be dominated by 4d → 5p transitions from the ground configurations of these ions and the resulting lines were identified with the aid of Hartree–Fock with configuration interaction calculations. Some features due to 4d → 5p transitions from the metastable configurations of ions Ce VI–Ce X were also observed.

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The photoabsorption spectra of Te I through to Te IV have been recorded in the extreme ultraviolet (EUV) region using the dual laser plasma (DLP) technique. Photoexcitation from the 4d subshell is the dominant process in the 50 to 130 eV region. Above the 4d ionization thresholds the spectra were found to be dominated by a 4d →ϵf shape resonance which peaks at 88 eV in each case, indicating that complete 4f ‘collapse’ has not occurred in stages up to and including Te3+. A transfer of oscillator strength from the resonance to the pseudo-discrete 4d →nf (n ⩾ 4) transitions with increasing ionization is evident from Te2+ onwards with the transition being the strongest feature in the Te IV spectrum. Time-dependent local density approximation (TDLDA) calculations successfully account for the shape resonance while Hartree–Fock with configuration interaction calculations permit identification of the discrete features.