Adam Brandt is an alumnus of PAMS, graduating in 2014 with a BS in Physics. He recently finished his PhD studies at Colorado State University in atomic physics, and now works at NIST in the Ion Storage group.
Over the past decade, there has been renewed interest in precision spectroscopy of atomic hydrogen and hydrogen-like species due to the so-called proton radius puzzle. The proton radius puzzle arose largely due to a measurement of the Lamb shift on muonic hydrogen, a hydrogen atom where the electron is replaced a muon, which resulted in a determination of the proton radius that was in significant statistical disagreement with the proton radius obtained from hydrogen spectroscopy at the time. We present a new measurement of the 2S1/2–8D5/2 transition with a cryogenic hydrogen beam, and the spectroscopy laser directly referenced to a coherent optical frequency comb. The measured resonance frequency is ?=770649561570.8(2.0) kHz, which corresponds to a relative uncertainty 2.5×10-12. Combining our result with the most recent measurement of the 1S–2S transition, we find a proton radius of rp=0.8581(50) fm and a Rydberg constant of R8=10973731.568330(52) m-1. Our result has a 3.4 s disagreement with the proton radius obtained from the muonic hydrogen Lamb shift measurement and a combined 1.8 s disagreement with the 2014 hydrogenic world average.
This seminar will be held in Kemper 206.