Speaker
Description
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).
