Session KP01 - Poster Session III.
POSTER session, Tuesday afternoon, March 23
Exhibit Hall, GWCC
There is now a ten standard deviation discrepancy between the measured value of the 2S Lamb shift in singly-ionized hydrogen-like helium [1] and the value calculated from quantum electrodynamics (QED) [2,3]. Recent Lamb shift measurements in atomic hydrogen [4,5,6] are not sensitive to the QED terms responsible for the discrepancy because of the uncertainty in the measured value of the proton charge radius, and measurements in hydrogen-like systems with Z higher than 2 do not have sufficient accuracy to address the problem. This serious situation is the motivation for a new experiment to determine the He^+ 2S Lamb shift using Doppler-free two-photon laser spectroscopy of the 2S-3S transition. We will report progress on this new measurement .
[1] A. van Wijngaarden, J. Kwela, and G.W.F. Drake, Phys. Rev. A43, 3325 (1991). [2] K. Pachucki et al., J. Phys. B 29, 177 (1996). [3] S. Mallampalli and J. Sapirstien, Phys. Rev. Lett. 80, 5297, (1998). [4] D.J. Berkeland, E.A. Hinds and M.G. Boshier, Phys. Rev. Lett. 75, 2470, (1995). [5] S. Bourzeiz et al., Phys. Rev. Lett. 76, 384, (1996). [6] Th. Udem et al., Phys. Rev. Lett. 79, 2646, (1997).