Analyses of the Sn IX–Sn XII spectra in the EUV region

Abstract

The Sn IX–Sn XII spectra excited in a vacuum spark have been analysed in the 130–160 Å wavelength region. The analysis was based on the energy parameter extrapolation in the isonuclear Sn VI–VIII and Sn XIII–XIV sequence. 266 spectral lines belonging to the 4dm–(4dm−14f+4p54dm+1) (m=6–3) transition arrays were classified in the Sn IX–Sn XII spectra for the first time. All 18 level energies of the 4d3 configuration and 39 level energies of the strongly interacting 4d24f and 4p54d4 configurations were established in the Sn XII spectrum. The energy differences between the majority of the 4dm levels and about 40 levels of the 4dm−14f+4p54dm+1 configurations were determined in each of the Sn IX, Sn X and Sn XI spectra (m=6–4). As a result, all intense lines were classified in the 130–140 Å region relevant to the extreme ultraviolet (EUV) lithography. It was shown that the most of the intense lines in the 2% bandwidth at 135 Å belong to the transitions in the Sn XI–Sn XIII spectra.