Fine structure energies for the 1s2s 3S-1s2p 3P transition in helium-like ions

• Published in: Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms Beam interactions with materials and atoms, 1995-05, Vol.98 (1), p.28-32
• Main Authors: Livingston, A.E., Kukla, K.W., Vogel Vogt, C.M., Berry, H.G., Dunford, R.W., Gemmell, D.S., Kanter, E.P., Suleiman, J., Ali, R., Cheng, S., Curtis, L.J.
• Format: Article
• Language: English
• ISSN: 0168-583X; 1872-9584
• DOI: 10.1016/0168-583X(95)00025-9

We have measured the 1s2s 3S 1-1s2p 3P 0 and 1s2s 3S 1-1s2p 3P 2 fine structure transition wavelengths in the helium-like Ar 16+ ion, using the beam-foil spectroscopy technique with position-sensitive photon detection. The wavelength results have precisions of < 30 ppm and are sensitive to the total QED corrections to < 0.5%. The measurements confirm the significance of ( Zα) 4-dependent relativistic corrections to the n = 2 state fine structures suggested by recent calculations. The small remaining discrepancies between these measurements and the accurate theoretical values suggest that the magnitude of uncalculated higher order QED terms is about 0.15( Zα) 4 a.u. The status of our experimental search for the 3S 1 3P 0 transition in Ni 26+ is discussed.