Measurement of 1s2s 3S1-1s2p 3P2,0 wavelengths in heliumlike silicon.

We have measured the vacuum-ultraviolet 1s2s 3 S 1 -1s2p 3 P 2.0 transition wavelengths in heliumlike neon by photographic spectroscopy of a recoil-ion source. The results are 1248. 10±0.01 and 1277.74±0.04 A, respectively, and are a sensitive test of present relativistic and quantum-electrodynamic calculations. Earlier photographic data have been reanalyzed for comparison with these results