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Abstract:
As previously calculated, the contribution of transitions between multiply excitedstates to the EUV(extreme ultraviolet)-spectrum of laser produced tinplasmas may be larger than initially presumed. Experimental data, probing line intensities for varying degrees of excitation, needs to be delivered for further investigation of this phenomenon. To achieve this, highly charged tin ions of several selected charge states (Sn11+-Sn15+) were produced and trapped inside an electron beam ion trap (EBIT) and brought into contact with electrons o varying kinetic energies during fast energy sweeps of up to 200 ms duration. The spontaneously emitted EUV-radiation around the industrially relevant 13.5 nmregion, following collisional excitation, was recorded and related to the electron energy. Projecting the intensity of each recorded spectral line onto the kinetic energy of the beam electrons, allowed extracting relative collisional excitation cross sections. Comparing this experimental data to both the results of fits employing multiple Van Regemorter relations as well as calculations using the collisional radiative model included in the flexible atomic code (FAC), additional energy thresholds for the production of EUV light in tin were found. Consequently the contribution of transitions between multiply excited states to the EUV spectrum were experimentally determined.
