Neutron resonance parameters of rubidium-85 and rubidium-87.

Abstract

High resolution neutron transmission and low background capture measurements were carried out on the separated rubidium isotopes, using the time-of-flight facility of the linear accelerator of Japan Atomic Energy Research Institute. Resonance parameters and associated quantities were deduced as follows: For 85Rb, gΓ n values were determined for 138 resonance levels in the energy region below 18.5 keV. s-wave strength function was obtained to be S0=(0.94±0.11)×10−4, average level spacing ≤D>=133±11 eV and average radiative width ≤Γ r >=328±18 me V. For 87Rb, gΓ n values were determined for 30 resonance levels in the energy region below 48.6 keV and the following quantities were deduced: S0=(1.15±0.3)×10−4, D=1,380±250 eV and ≤Γγ>=166±30 meV. For 85Rb average properties of resonances are in good agreement with the prediction of the statistical model. On the other hand, for 87R9b the average properties of resonances deviate from the prediction of the statistical model; four strong s-wave resonances cluster within an energy interval of 5 keV, and they carry about 37% of s-wave strength below 48.6 keV.