Neutron energy-dependent angular distributions were observed for individual γ rays from the 0.74 eV p-wave resonance of La139+n to several lower excited states of La140. The γ-ray signals were analyzed in a two-dimensional histogram of the γ-ray energy, measured with distributed germanium detectors, and neutron energy, determined with the time-of-flight of pulsed neutrons, to identify the neutron energy dependence of the angular distribution for each individual γ rays. The angular distribution was also found for a photopeak accompanied with a faint p-wave resonance component. Our results can be interpreted as interference between s- and p-wave amplitudes, which may be used to study discrete symmetries of fundamental interactions.
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