Highly resolved EUV beam-foil spectra of silicon

Spectra of foil-excited ions at tandem energies in the EUV region show many unclassified lines. In order to provide a basis for term analysis, high resolution spectra of Si are taken using a ruled 600 l/mm grating in 3^rd diffraction order and two holographic gratings of 1,200 l/mm resp. 3,600 l/mm in first diffraction order. With the latter grating the resolution power of a 2.2 m grazing-incidence monochromator is sufficient to measure fine-structure splittings of inter-shell transitions of O VI–O VIII and Si X–Si XII in the wavelength rangeλ < 20 nm. The performance of the gratings is demonstrated.