E. G. Myers

Measurement of wavelengths in helium-like sulphur

We have used photographic spectroscopy of a beam - foil source to measure the vacuum ultraviolet 1s2s - 1s2p transition wavelengths in helium-like sulphur. The results are A and A, respectively. These measurements, together with our earlier measurements in helium-like silicon and phosphorus, are compared with other precision measurements for Z = 14 to 18, and with recent relativistic and quantum electrodynamic calculations.

Measurement of the 1s2s 1S0−1s2p 3P0,1 transitions in heliumlike nitrogen by fast-beam laser spectroscopy

For a large range of Z the intercombination 1s2s 1S0−1s2p 3P1 interval in heliumlike ions is accessible to spectroscopy with infra-red lasers. Using a CO2 laser and a nitrogen ion beam from a Van de Graaff accelerator, together with careful energy calibration, we obtained 986.321(7) cm−1 for the N5+, 21S0−23P1 transition. This result is a severe test of two-electron Lamb Shift calculations. In 14N5+ there is also sufficient hyperfine mixing of the 23P0 and 23P1 levels to permit spectroscopy of the otherwise totally forbidden 21S0−23P0 interval. By careful choice of CO2 laser line it was possible to observe the 21S0−23P0 and the 21S0−23P1,F=2 transitions at similar ion beam energies, yielding a precise result for the 23P1−23P0 fine-structure interval of 8.6709(10) cm−1. This result provides a test of current calculations of QED contributions of order α7mec2, which are required for obtaining a new value of the finestructure constant from the finestructure of helium.