Speaker
Description
The hydrogen atom has emerged as an ideal candidate for precision measurements of fundamental constants, since its energy levels can be calculated with high accuracy owing to its simple structure. Spectroscopy of two transitions of hydrogen provides a means to determine the precise values of the Rydberg constant $R_{\infty}$ and the proton charge radius $r_p$, and further comparison with other transitions proves to be a test for QED theory itself [1]. One of the most vital requirements for such precision experiments is a stable source of atomic hydrogen and a method for precisely quantifying its population. In this poster, we provide an overview of the methods to characterise our atomic hydrogen beam in the 1S-3S Two-Photon Direct Frequency Comb Spectroscopy Experiment for hydrogen at MPQ [2]. This includes Optical Emission spectroscopy of the hydrogen plasma, which dissociates molecular hydrogen to atomic hydrogen in our experiment. The atomic and molecular hydrogen populations in the plasma are estimated from their respective optical emissions, i.e., Balmer lines and Fulcher bands [3] [4], and their dependence on various experimental parameters is systematically analysed. In addition, a Calorimetric Wire Detector is being developed for in situ detection of atomic hydrogen with minimal disturbance to the beam. This detector quantifies the degree of dissociation by measuring the change in resistance of a very thin wire due to the heat released from the recombination of atomic hydrogen on its surface [5]. We present preliminary results on detecting atomic hydrogen using the wire detector's resistance signal.
References:
[1] P. J. Mohr, E. Tiesinga, D. B. Newell, and B. N. Taylor, Codata internationally recom-
mended 2022 values of the fundamental physical constants (2024).
[2] A. Grinin, A. Matveev, D. C. Yost, L. Maisenbacher, V. Wirthl, R. Pohl, T. W. Hänsch, and T. Udem, Science 370, 1061 (2020).
[3] U. Fantz, Plasma Sources Science and Technology 15, S137 (2006).
[4] J.-J. Dang, K.-J. Chung, and Y. S. Hwang, Review of Scientific Instruments 87, 053503 (2016).
[5] D. Brenner, Review of Scientific Instruments 40, 1234 (1969).