Sixt Tobias, Guan Jiwen, Tsoukala Alexandra, Hofsäss Simon, Muthu-Arachchige Thilina, Stienkemeier Frank, Dulitz Katrin
Institute of Physics, University of Freiburg, Hermann-Herder-Str. 3, 79104 Freiburg, Germany.
Rev Sci Instrum. 2021 Jul 1;92(7):073203. doi: 10.1063/5.0048323.
We compare two different experimental techniques for the magnetic-sub-level preparation of metastable He in the 2S level in a supersonic beam, namely, magnetic hexapole focusing and optical pumping by laser radiation. At a beam velocity of v = 830 m/s, we deduce from a comparison with a particle trajectory simulation that up to 99% of the metastable atoms are in the M = +1 sub-level after magnetic hexapole focusing. Using laser optical pumping via the 2P-2S transition, we achieve a maximum efficiency of 94% ± 3% for the population of the M = +1 sub-level. For the first time, we show that laser optical pumping via the 2P-2S transition can be used to selectively populate each of the three M sub-levels (M = -1, 0, +1). We also find that laser optical pumping leads to higher absolute atom numbers in specific M sub-levels than magnetic hexapole focusing.
