20-25 October 2019
Europe/Zurich timezone

Manipulating the translational and internal degrees of freedom of hydrogen atoms

22 Oct 2019, 17:35
WHGA/001 - Auditorium (PSI)

WHGA/001 - Auditorium



Mr Simon Scheidegger (ETH Zurich)


The first experiments designed to control the translational motion and the internal state of the hydrogen atom were performed almost 100 years ago by Rabi [1] using the beam methods developed by Gerlach and Stern [2]. We present a method with which paramagnetic atoms and molecules can be generated in a specific magnetic sublevel of a selected internal state and with which the atom or molecule velocity can be manipulated at will. The selected magnetic state and velocity is achieved by multistage Zeeman deceleration [3, 4].
Of particular interest are slow beams ($v$ ≤ 300$\,$m$\,$s$^{−1}$) of cold hydrogen atoms in view of precision frequency measurements of fine- and hyperfine structure intervals as well as intervals to high-Rydberg states, which are relevant in the context of the proton charge-radius puzzle [5, 6]. In our experiment we generate the hydrogen atoms by photodissociation of NH$_{3}$ in a capillary mounted at the orifice of a pulsed valve. The hydrogen atoms are entrained in the supersonic expansion of a rare gas and enter a multistage Zeeman decelerator, with which they are slowed down from initially 500$\,$m$\,$s$^{−1}$ to 50 - 100$\,$m$\,$s$^{−1}$ [7]. After leaving the decelerator they are photoexcited to $n$p-Rydberg states in a 2+1’ resonant three-photon excitation sequence via the 2s $^{2}$S$_{1/2}$ (F = 0, 1) intermediate state and detected by pulse-field ionization. We will report on our experimental progress on the precision measurements of $n$p-2s transition frequencies.

[1] I. I. Rabi, J. M. B. Kellogg, and J. R. Zacharias, Phys. Rev. 46, 157 (1934).
[2] W. Gerlach and O. Stern, Z. Phys. 9, 349 (1922).
[3] N. Vanhaecke, U. Meier, M. Andrist, B. H. Meier, and F. Merkt, Phys. Rev. A 75, 031402(R) (2007).
[4] P. Jansen et al., Phys. Rev. Lett. 115, 133202 (2015).
[5] R. Pohl et al., Nature 466, 213 (2010).
[6] A. Beyer et al., Science 358, 79 (2017).
[7] S. D. Hogan, A. W. Wiederkehr, M. Andrist, H. Schmutz, and F. Merkt, J. Phys. B: At. Mol. Opt. Phys. 41, 081005 (2008).

Primary author

Mr Simon Scheidegger (ETH Zurich)


Dr Paul Jansen (ETH Zurich) Mr Josef A. Agner (ETH Zurich) Mr Hansjürg Schmutz (ETH Zurich) Frédéric Merkt (ETH Zurich, Laboratory of Physical Chemistry)

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