Total Neutron Cross Section of Xe135 as a Function of Energy
Abstract
The total neutron cross section of Xe135 as a function of energy has been remeasured at Oak Ridge National Laboratory under more favorable conditions than obtained in earlier measurements. A sample thickness of 2.5×1018 atoms of Xe135 gas per cm2 was procured from the gases generated in a homogeneous reactor. A mechanical time-of-flight chopper was used to select neutrons in the energy range from 0.01 ev to several thousand ev. The number of Xe135 atoms in the sample was determined by means of mass spectrometer measurements on the long-lived daughter, Cs135. The data of the low-energy resonance were fitted to the single-level Breit-Wigner formula, taking into account Doppler corrections, equally well with the following two sets of parameters: statistical weight factor g=38; resonance energy ɛ0=0.08472+/-0.00027 ev; neutron width at energy ɛ0, Γn0=0.03477+/-0.00021 ev; capture width, Γα=0.083303+/-0.00062 ev; for g=58, ɛ0=0.08415+/-0.00028 ev; Γn0=0.02057+/-0.00012 ev; Γa=0.09493+/-0.00071 ev. The errors quoted are the standard deviations derived from the statistics of the measurements. Systematic errors are discussed in the body of the paper. No evidence for resonances at energies greater than 0.085 ev was observed. The results described are interpreted in terms of recent considerations on the statistics of the properties of nuclear energy levels.
- Publication:
-
Physical Review
- Pub Date:
- September 1959
- DOI:
- 10.1103/PhysRev.115.1693
- Bibcode:
- 1959PhRv..115.1693S