Relativistic Configuration-Interaction and Perturbation Theory Calculations of the Sn XV Emission Spectrum

Abstract

Recently, there has been increased interest in developing advanced bright sources for lithography. Sn ions are particularly promising due to their bright emission spectrum in the required wavelength range. Cowan’s code has been used to model the emission; however, it has adjustable parameters, which limit its predictive power, and it has limited relativistic treatment. Here, we present calculations based on ab initio relativistic configuration-interaction many-body perturbation theory (CI-MBPT), with relativistic corrections included at the Dirac-Fock level and core-polarization effects with the second-order MBPT. As a proof of principle that the theory is generally applicable to other Sn ions with proper development, we focused on one ion where direct comparison with experimental observations is possible. The theory can also be used for ions of other elements to predict emissions for optimization of plasma-based bright sources.

Review of the 1st EUV Light Sources Code Comparison Workshop

“…It is well known that the atomic structures of Sn 10+ -Sn 14+ ions are subject to strong configuration effects, and this makes their accurate calculation notoriously difficult [20,66]. Extensive benchmarking of these level structures with charge state-specific experimental spectra [67][68][69][70][71] and/or highly accurate ab initio atomic structure calculations [70,72,73] is very much required. Experimental measurements of emission from multiply excited states are also highly desired given their dominant contribution to EUV emission from laser-driven, mid-Z plasmas [23,74,75].…”