An Extremum Principle for a Neutron Diffraction Experiment
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Gregg Jaeger
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Photonics Center, 8 St. Mary's St., 
Dept. of Electrical and Computer Engineering,
Boston University,
Boston MA 02215
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Abner Shimony
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Departments of Philosophy and Physics,
Boston University,
Boston MA 02215
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A variational formulation of the Schroedinger Equation is shown to provide
a direct justification of a practical rule for analyzing a neutron diffraction
experiment of Finkelstein analyzed by Horne, Finkelstein, Shull, Zeilinger and
Bernstein. The experiment in question exhibited an enhancement of the effect 
of the spin-orbit interaction with the radial electric field of a nucleus or 
complete atom due to a resonance effect arising when neutrons fulfill Bragg's 
condition in entering a crystal immersed in a strong magnetic field.
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(To appear in Foundations of Physics)