Northwestern University

Oct
6
Fri 4:00 PM

Thomas Udem: Precision Spectroscopy of Atomic Hydrogen and the Proton Radius Puzzle

When: Friday, October 6, 2017
4:00 PM - 5:00 PM  

Where: Technological Institute, L211, 2145 Sheridan Road, Evanston, IL 60208 map it

Audience: Faculty/Staff - Student - Public - Post Docs/Docs - Graduate Students

Contact: Yassaman   847.491.7650

Group: Physics and Astronomy Colloquia

Category: Academic

Description:

Title: Precision Spectroscopy of Atomic Hydrogen and the Proton Radius Puzzle

Speaker: Thomas Udem, Max-Planck Institut fuer Quantenoptik

Abstract: Precise determination of transition frequencies of simple atomic systems are required for a number of fundamental applications such as tests of quantum electrodynamics (QED), the determination of fundamental constants and nuclear charge radii. The sharpest transition in atomic hydrogen occurs between the metastable 2S state and the 1S ground state with a natural line width of only 1.3 Hz. Its transition frequency has now been measured with almost 15 digits accuracy using an optical frequency comb and a cesium atomic clock as a reference [1]. A recent measurement of the Lamb shift in muonic hydrogen is in signicant contradiction to the hydrogen data if QED calculations are assumed to be correct [2]. In order to shed light on this discrepancy the transition frequency of one of the broader lines in atomic hydrogen has to be measured with very good accuracy. For this purpose we have employed our previous 1S-2S apparatus as a cold source of laser excited 2S atoms in order to perform spectroscopy on the 2S-4P transitions. With a natural line width of 12.7 MHz, large Doppler eects, quantum interference etc. a good line shape analysis is mandatory to identify the true transition frequency. Analyzing our initial data yields a proton radius that is compatible with the value obtained from muonic hydrogen with an uncertainty comparable to the previous hydrogen world data.

Host: Gabrielse

Speaker Schedule

Keywords: Physics, Astronomy, colloquium

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