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A: Fachverband Atomphysik

A 15: Poster I

A 15.1: Poster

Dienstag, 3. März 2009, 16:30–19:00, VMP 9 Poster

Frequency comb spectroscopy of Hydrogen 1S-3S — •Elisabeth Peters¹, Sascha Reinhardt¹, Scott Diddams², Thomas Udem¹, and Theodor W. Hänsch¹ — ¹Max-Planck-Institut für Quantenoptik, Garching, Germany — ²National Institute of Standards and Technology

Precise spectroscopy of atomic hydrogen allows us to test fundamental theories as the quantum electro dynamics (QED). Decades of precise comparisons with experiments have established this theory in physics.
The comparison of the narrow 1S-2S transition frequency, which has reached the uncertainty of 1.4 parts in 10¹⁴, and determination of the Rydberg constant and the Lamb shift are presently limited by the large uncertainty in the proton charge radius. To overcome this limitation we set up an experiment to measure the absolute frequency of the 1S-3S two photon transition at 205nm.
The required UV light at 205nm is generated by two successive resonant enhanced second harmonic generations (SHG) of a mode locked titanium sapphire laser. The spectrum of such a mode locked laser features equidistant frequency modes, which can be used for the high precision spectroscopy.