Heidelberg 2015 – wissenschaftliches Programm
A 13.7: Vortrag
Dienstag, 24. März 2015, 12:45–13:00, M/HS1
Frequency metrology of ultracold 3 He and 4 He in the framework of the proton radius puzzle — •Robert J. Rengelink, Remy P.M.J.W. Notermans, and Wim Vassen — LaserLaB, Department of Physics and Astronomy, VU University, Amsterdam, the Netherlands
Ultracold gases can be probed with long interrogation times which allows very weak optical transitions to be made. In helium narrow transitions involving S-states are of interest from the perspective of testing QED and as a sensitive probe of the nuclear charge radius. At VU university we study the doubly forbidden 2 3S → 2 1S transition at 1557 nm, which allows an accurate determination of the 3 He-4 He differential nuclear charge radius. Previously, this transition was measured to kHz accuracy in our group (van Rooij et. al, Science 333,196 (2011)). To achieve a level of accuracy comparable to the projected accuracy of muonic helium experiments currently being performed at the Paul Scherrer Institute (Nebel et. al, Hyperfine Interact. 212, 195-201(2012)) we intend to push the accuracy to the 0.1 kHz level.
In this contribution, I will discuss the improvements currently being implemented in our experiment. These include an improved laser frequency stabilization scheme, a better determination of the Zeeman shift and, most importantly, the implementation of a magic wavelength dipole trap at 320 nm (Notermans et. al, Phys. Rev. A 90, 052508 (2014)) to eliminate the AC-stark shift. For this purpose a laser system has been built with a continuous output power of 2W at this challenging UV wavelength.