Precision Measurement of the 29Si, 33S, and 36Cl Binding Energies
Scheme of the radiative neutron capture.Whenever a nucleus captures a slow neutron, a compound nucleus is formed. The excitation energy is close to the binding energy. The compound nucleus decays by emitting gamma-rays in a cascade.
Table of results showing the improvement in accuracy provided by GAMS measurements.
Precision Measurement of the 29Si, 33S, and 36Cl Binding Energies
The binding energies of 29Si, 33S, and 36Cl have been measured with a relative uncertainty < 0.65 x 10−6 using the GAMS4 flat-crystal spectrometer. The unique features of these measurement are
- nearly perfect crystals whose lattice spacing is known in meters,
- a highly precise angle scale that is derived from first principles,
- a gamma-ray measurement facility that is coupled to a high flux reactor with near-core source capability.
The binding energy is obtained by measuring all gamma-rays in a cascade scheme connecting the capture and ground states. The measurements require the extension of precision flat-crystal diffraction techniques to the 5 to 6 MeV energy region, a significant precision measurement challenge. The measured binding energies have an uncertainty that is significantly less (factors of 7, 67, and 16 for 29Si, 33S, and 36Cl respectively) than the uncertainty that is associated with binding energies determined from atomic mass tables.
Ref.: Dewey M.S., Kessler E.G., Deslattes R.D., Börner H.G., Jentschel M., Doll C., Mutti P.; Physical Review C 73, 044303-1-044303-11 (2006)