Investigation of a possible hyperfine splitting in the hydrogen molecule at neV energies -- precursor to a hfs spectrometer using UCN
In previous experiments at the ILL the transmission of ultracold neutrons (UCN) through liquid and solid ortho-deuterium was measured. While the general 1/v-behavior of the scattering cross section in ortho-D2 was confirmed, i.e. the cross section is inversely proportional to the neutron speed in the UCN energy range, we also observed a peak at around E_kin = 170 neV in both the solid and liquid deuterium data sets. This peak is also visible in the data taken by a PSI group in 2004, who used a different experimental setup. It stems very probably from the hyperfine splitting (hfs) of the deuterium molecule. The experiment proposed here will provide proof of whether or not the peak observed at 170 neV in ground-state ortho-deuterium (J = 0) and the equivalent peak in hydrogen both stem from an inelastic excitation. If the experiment at IN16B is successful, it will be conclusive proof that hfs splitting in the low-neV energy range can be directly detected with ultracold neutrons. To our knowledge, this has never been done before.
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Stefan Döge; Bernhard Frick; GUTSMIEDL Erwin; KUHLMANN Kristijan and MORKEL Christoph. (2017). Investigation of a possible hyperfine splitting in the hydrogen molecule at neV energies -- precursor to a hfs spectrometer using UCN. Institut Laue-Langevin (ILL) doi:10.5291/ILL-DATA.1-10-30
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