We observed the 19 keV neutron decay from the 3.388-MeV state of B12 by measuring B11-neutron coincidences in colinear geometry at several angles. The ratio of this yield to the yield of particle-stable B12 nuclei is a measure of the excitation energy of B12 fragments produced in the reaction. The extreme kinematic focusing of the 19-keV decay enabled us to obtain the dependence of this ratio on fragment kinetic energy. For B12 nuclei emitted with kinetic energies EA15 MeV the ratio is surprisingly constant; for B12 nuclei of higher kinetic energy it decreases monotonically.
ASJC Scopus subject areas
- Nuclear and High Energy Physics