MEASUREMENT OF 1S2S S-3(1)-1S2P P-3(2,0) WAVELENGTHS IN HELIUM-LIKE SILICON

We have measured the vacuum-ultraviolet 1s2s S-3(1)-1s2p P-3(2,0) tran sition wavelengths in heliumlike silicon by photographic spectroscopy of a beam-foil source. The results are 814.71 +/- 0.02 angstrom and 97 8.68 +/- 0.03 angstrom, respectively, and represent a sensitive test o f present relativistic and quantum electrodynamic calculations. Compar isons are made between our results, previous measurements of these tra nsitions, and the current theories. Good agreement is obtained, partic ularly with recent relativistic many-body perturbation calculations. A discussion of future measurements of this interval is also presented.