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Theory of inelastic scattering of cold neutrons from liquid helium

Cohen, Michael and Feynman, Richard P. (1957) Theory of inelastic scattering of cold neutrons from liquid helium. Physical Review, 107 (1). pp. 13-24. ISSN 0031-899X. doi:10.1103/PhysRev.107.13.

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A measurement of the energy losses of monoenergetic neutrons scattered from liquid He II would permit a determination of the energy-versus-momentum relation for the elementary excitations (phonons and rotons) in the liquid. A major part of the scattering at a fixed angle arises from production or annihilation of a single excitation and appears as sharp lines in the energy spectrum. From the position of these lines the energy-versus-momentum relation of the excitations can be inferred. Other processes, such as production or annihilation of multiple excitations, contribute a continuous background, and occur at a negligible rate if the incident neutrons are slow (λ~>4A) and the helium cold (T<2°K). The total cross-section data can be accounted for by production of single excitations; the theoretical cross section, computed from a wave function previously proposed to represent excitations, agrees with experiment over the entire energy range, within 30%. Line widths in the discrete spectrum are negligible at 1°K because of the long lifetime of phonons and rotons.

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Additional Information:©1957 The American Physical Society. Received 25 March 1957. We wish to thank P. J. Bendt, M. Gell-Mann, W. J. Karzas, and H. Palevsky for valuable discussions.
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:6093
Deposited By: Tony Diaz
Deposited On:17 Nov 2006
Last Modified:08 Nov 2021 20:31

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