Karl-Heinz Schartner

Determination of absolute emission cross sections for electron-impact-induced line radiation in the vacuum ultraviolet

A method and an experimental setup have been developed for measuring absolute photoemission cross sections for electron-impact-induced line radiation in the vacuum ultraviolet (VUV). Unparalleled low uncertainties for the cross sections were achieved mainly from the use of the Berlin electron storage ring as a primary standard source in the VUV for the determination of the responsivity of the spectrometer-detector system used and from the use of a spinning rotor gauge as a secondary standard for the determination of the target gas density. As the first result we present a photoemission cross section for the Ar II 3s3p(6)(2)S(½)-3s(2)3p(5)(2)p?(3/2) transition at 91.98 nm for 2-keV electron-impact energy of 1.167 × 10(-18) cm(2) with a relative uncertainty of 4.4% (√3σ value). This low uncertainty demonstrates the suitability of the setup for further cross-section measurements.

Outer s-shell ionization of neon, argon and krypton by N+, Ne+ and Ne2+ impact

The outer s-shell ionization of neon, argon and krypton has been studied by N+ and Ne+ impact in the energy range of 100 keV to 1000 keV, and by Ne2+ on Ne from 300 keV to 1800 keV. For the Ne+-Ne system the 2s vacancy production has been studied for the projectile and target separately. In connection with theoretical calculations of Albat et al. (see ibid., vol.8, p.2520 (1975)), the Ne+-Ne measurements allow the statement that the quasi-molecule model holds for this process up to relative velocities of 0.7 au.