Kinematically complete experimental study of Compton scattering at helium atoms near the threshold

Compton scattering is one of the fundamental interaction processes of light with matter. When discovered1, it was described as a billiard-type collision of a photon ‘kicking’ a quasi-free electron. With decreasing photon energy, the maximum possible momentum transfer becomes so small that the corresponding energy falls below the binding energy of the electron. In this regime, ionization by Compton scattering becomes an intriguing quantum phenomenon. Here, we report on a kinematically complete experiment studying Compton scattering off helium atoms in that regime. We determine the momentum correlations of the electron, the recoiling ion and the scattered photon in a coincidence experiment based on cold target recoil ion momentum spectroscopy, finding that electrons are not only emitted in the direction of the momentum transfer, but that there is a second peak of ejection to the backward direction. This finding links Compton scattering to processes such as ionization by ultrashort optical pulses2, electron impact ionization3,4, ion impact ionization5,6 and neutron scattering7, where similar momentum patterns occur. © 2020, The Author(s), under exclusive licence to Springer Nature Limited.

Kircher M.1 , Trinter F.2, 3 , Grundmann S.1 , Vela-Perez I.1 , Brennecke S.4 , Eicke N.4 , Rist J.1 , Eckart S.1 , Houamer S.5 , Chuluunbaatar O. 6, 7, 8 , Popov Y.V. 6, 9 , Volobuev I.P.9 , Bagschik K.2 , Piancastelli M.N.10, 11 , Lein M.4 , Jahnke T.1 , Schöffler M.S.1 , Dörner R.1
Nature Research
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  • 1 Institut für Kernphysik, J. W. Goethe Universität, Frankfurt, Germany
  • 2 FS-PETRA-S, Deutsches Elektronen-Synchrotron DESY, Hamburg, Germany
  • 3 Molecular Physics, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin, Germany
  • 4 Institut für Theoretische Physik, Leibniz Universität Hannover, Hannover, Germany
  • 5 LPQSD, Department of Physics, Faculty of Science, University Sétif-1, Setif, Algeria
  • 6 Joint Institute for Nuclear Research, Dubna, Moscow, Russian Federation
  • 7 Institute of Mathematics and Digital Technologies, Mongolian Academy of Sciences, Ulaanbaatar, Mongolia
  • 8 Peoples’ Friendship University of Russia (RUDN University), Moscow, Russian Federation
  • 9 Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University, Moscow, Russian Federation
  • 10 Sorbonne Universités, CNRS, UMR 7614, Laboratoire de Chimie Physique Matière et Rayonnement, Paris, France
  • 11 Department of Physics and Astronomy, Uppsala University, Uppsala, Sweden
Binding energy; Compton scattering; Electrons; Helium; Ion bombardment; Ions; Momentum; Momentum transfer; Neutron scattering; Photons; Cold target recoil ion momentum spectroscopies; Complete experiment; Electron impact-ionization; Interaction process; Ion-impact ionization; Momentum correlation; Quasi-free electron; Ultrashort optical pulse; Impact ionization
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Parfenov V.A., Khesuani Y.D., Petrov S.V., Karalkin P.A., Koudan E.V., Nezhurina E.K., Pereira F.D.A.S., Krokhmal A.A., Gryadunova A.A., Bulanova E.A., Vakhrushev I.V., Babichenko I.I., Kasyanov V., Petrov O.F., Vasiliev M.M., Brakke K., Belousov S.I., Grigoriev T.E., Osidak E.O., Rossiyskaya E.I., Buravkova L.B., Kononenko O.D., Demirci U., Mironov V.A.
Science Advances. American Association for the Advancement of Science. Vol. 6. 2020.