Measurement of 1s2s 3S1–1s2p 3P2,0 wavelengths in heliumlike argon

Abstract We have used photographic spectroscopy of a recoil-ion source to perform a measurement of the vacuum ultra-violet 1s2s 3 S 1 –1s2p 3 P 2,0 transition wavelenghts in heliumlike argon. The results are 559.95 ± 0.02 A and 661.58 ± 0.02 A respectively. This measurement constitutes a sensitive test of current relativistic and quantum electrodynamic calculations.