The thermal neutron scattering cross section of 86Kr

The availability of 27 1 STP krypton-86 gas, an isotope with unknown thermal neutron scattering cross section, was an excellent occasion to determine the (bound atom) scattering cross section and its coherent part by application of the neutron transmission method and neutron interferometry. The transmission method was applied in a diffractometer, a Larmor spectrometer and a TOF-spectrometer. In addition to 86Kr also natural krypton (nKr) was used for sample in the diffractometer. The diffractometer measurements result in bound atom scattering cross sections σs=8.92(46) b for 86Kr and σs=7.08(95) b for nKr. The Larmor transmission measurements lead to a final result σs=8.44(9) b for 86Kr. In the TOF-spectrometer the wavelength-dependent total cross section of water was determined. Coherent neutron scattering lengths were determined using the neutron interferometry method with a skew symmetric neutron interferometer. Scans with 86Kr and nKr led to bc=8.07(26) fm for 86Kr and 7.72(33) fm for nKr, corresponding to coherent scattering cross sections σc=8.18(53) b and 7.49(64) b respectively. Due to the large errors in the bound atom scattering cross section and coherent scattering cross section of 86Kr and nKr, the incoherent cross section of both gases, σi = 0 within its inaccuracy, σi=0.26(54) b for 86Kr and σi=0.41(1.15) b for nKr. (orig.)