Grant: Discovery Grants Program - Individual

Measurement of the Lamb shift in atomic hydrogen to determine the charge radius of the proton:We will measure the 2S-to-2P intervals in atomic hydrogen to an accuracy of 2 kHz using the Ramsey technique of separated oscillatory fields (SOF), improving on the 1980 measurement of Lundeen and Pipkin. Our measurements, along with existing highly-precise QED theory, will each lead to a 0.6% determination of the proton charge radius, shedding light on the 4.3% (7 sigma) discrepancy between a proton radius obtained using muonic hydrogen and one from hydrogen spectroscopy and electron-proton scattering.Measurement of the fine-structure of atomic helium to determine the fine-structure constant:We have performed subnatural linewidth microwave measurements of the n=2 triplet P fine structure of helium using SOF (PRA 79, 060503). We have now devised a detection scheme that involves direct detection of the n=2 triplet P atoms by resonant transfer of these atoms to a previously emptied metastable n=2 triplet S sublevel, which allows for higher detection efficiency and lower background, and which removes the largest systematic effect in our measurement. We expect to improve our 350-Hz accuracy to better than 30 Hz, which will provide an important test of QED and lead to a 0.5 part-per-billion determination of the fine-structure constant. Additionally, we have identified a previously overlooked systematic effect due to quantum mechanical interference from distant neighboring resonances that is important for measurements of these intervals and for a large range of other precision measurements.Precise spectroscopy of trapped antihydrogen: a test of CPT symmetry and of antimatter physics:Our group at York continues an active participation in the ATRAP (a collaboration between Harvard, Mainz, Julich and York led by G. Gabrielse). ATRAP has now been successful in 2 of its 3 goals: production of cold antihydrogen (PRL 89, 213401) and trapping of these atoms in a Ioffe trap (PRL 108, 113002). The third goal of performing precise spectroscopy on these atoms remains.