# 2019 CAP Congress / Congrès de l'ACP 2019

2-7 June 2019
Simon Fraser University
America/Vancouver timezone
Welcome to the 2019 CAP Congress Program website! / Bienvenue au siteweb du programme du Congrès de l'ACP 2019 !

## A measurement of the Lamb shift in atomic hydrogen and its implication for the proton size puzzle

Jun 3, 2019, 10:45 AM
30m
BLU 10011 (Simon Fraser University)

### BLU 10011

#### Simon Fraser University

Invited Speaker / Conférencier(ère) invité(e) Division of Atomic, Molecular and Optical Physics, Canada / Division de la physique atomique, moléculaire et photonique, Canada (DAMOPC-DPAMPC)

### Speaker

Prof. Eric A. Hessels (York University)

### Description

We have measured the $n$=2 Lamb shift in atomic hydrogen. The measurement uses a direct microwave transition between the 2S and 2P states, and employs the new frequency-offset separated-oscillatory-fields (FOSOF) technique. The FOSOF technique is a variation of the Ramsey separated-oscillatory field technique in which the two separated fields have their frequencies slightly offset from each other. Our Lamb shift measurement, along with existing high-precision quantum-electrodynamics theory, leads to a precise measurement of the rms proton charge radius, and therefore helps to resolve the eight-year-old puzzle created by contradictory determinations of the proton size. In particular, this measurement is the direct analog of the very precise 2S-2P muonic-hydrogen determination of the proton size. Our recent work in determining the helium 2$^3$P fine structure and our new program to determine the electron electric dipole moment will also be discussed briefly.

### Primary author

Prof. Eric A. Hessels (York University)

### Presentation materials

There are no materials yet.