12-16 October 2015
Hungarian Academy of Sciences
Europe/Budapest timezone

Two-Photon Direct Frequency Comb Spectroscopy oft the 1s3s Transition in Hydrogen with an Absolute Accuracy of 17kHz.

Oct 14, 2015, 9:45 AM
Kis terem (Small conference room) (Hungarian Academy of Sciences)

Kis terem (Small conference room)

Hungarian Academy of Sciences

1051 Budapest, Széchenyi tér 9.


Alexey Grinin (MPQ Garching)


High precision spectroscopy has been always the driving force for new fundamental theories in physics. The so called proton size problem is a so far unexplained disagreement of the value of the proton charge radius extracted from the muonic spectroscopy, hydrogen spectroscopy and elastic electron-proton scattering by more than 5 sigma \cite{Antognini2013}. Our experiment is highly suitable to verify or falsify the true existence of this problem since it is based on a completely different spectroscopy method than previously performed hydrogen spectroscopy experiments. \newline In our experiment we were able recently to give a preliminary value of the 1s3s two-photon transition frequency with an accuracy of 17kHz for the first time with the Direct Frequency Comb Spectroscopy (DFCS) \cite{Baklanov1977}. This measurement was  limited by an so far unobserved effect, which occurs in DFCS with chirped pulses and atomic beams. It can be understood as Chirp-Induced First Order Residual Doppler Shift (FORDS) and it is an important effect for future XUV and VUV DFCS experiments. \newline In our setup we produce a frequency comb at 205 nm (2ps) by two subsequent frequency doubling cavities from a Ti:Sa mode-locked laser at 820 nm \cite{Peters2013}. The atomic beam of hydrogen atoms is excited in an enhancement cavity and photons from 3s2p transition are collected and detected.

Primary authors

Alexey Grinin (MPQ Garching) Dr Artur Matveev (MPQ Garching) Prof. Dylan Yost (Colorado State University) Prof. T.W. Hänsch (MPQ Garching) Dr Thomas Udem (MPQ Garching)

Presentation materials