Precision Wavelength Determination of 2¹<i>P</i>₁-1¹<i>S</i>₀and 2³<i>P</i>₁-1¹<i>S</i>₀Transitions in Helium-Like Sulfur Ions

Abstract

Transitions from the 21P1 - and 23P1 -state to the ground state 11S0 in helium-like sulphur ions have been measured with an accuracy of 4 × 10-5. Energy calibration is described in detail and two reference wavelengths have been reevaluated. Substantial line-blending was observed, due to long-lived spectator electrons. The two transition energies were corrected for Doppler shift and compared with most refined theoretical calculations, including terms of order α4Z6 in the Breit operator and terms of order α5Z6 in the quantum-electrodynamical corrections. The experimental contributions to the ground-state QED shifts agree within its error (∼ 15%) with the theoretical values.