Spin and Parity Assignment of Neutron Resonances using Gamma-ray Multiplicity

Abstract

Decay gamma rays following neutron capture on various isotopes are collected by the Detector for Advanced Neutron Capture Experiments (DANCE) array, which is located at flight path 14 at the Lujan Neutron Scattering Center at Los Alamos National Laboratory. The high segmentation (160 detectors) and close packing of the detector array enable gamma‐ray multiplicity measurements. The calorimetric properties of the DANCE array coupled with the neutron time‐of‐flight technique enables one to gate on a specific resonance of a given isotope in the time‐of‐flight spectrum and obtain the summed energy spectrum for that isotope. The singles gamma‐ray spectrum for each multiplicity can be separated by their DANCE cluster multiplicity. The multiplicity distribution contains the signatures of spin and parity of the capture state. Under suitable circumstances where the difference between spins of the initial (capture) and final (ground) state is large enough, the signatures in the multiplicity distribution can be used in improving the spin assignment of the initial state. The spin assignment is applied with varying degree of success to difference isotopes and description of this application for 95Mo, 151,153Eu, and 155,157Gd is reviewed briefly.