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KERNFORSCHUNGSZENTRUM KARLSRUHE (GERMANY)
INSTITUT FUR ANGEWANDTE KERNPHYSIK
3 MeV Van de Graaf
1.1. High Resolution Resonance Spectroscopy
G. Rohr, K-N. Müller
The measurements of the total neutron cross section of' separated
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isotopes with high resolution were continued. The elements Cr
and 7 Ti were measured in the energy range of 20 - 250 keV, the
copper isotopes in the range of kO r» 250 keV.
Figures 1 - h show the cross sections as a function of the energy
for these elements. The pronounced energy dependent background at
20 keV for the Ti - probe (enriched to ?6 %) is due to resonances
of the Ti isotope.
57 53
The analysis of the Fe and -^Cr data with the one channel multilevel
formula was started but not completed. In the cross sections
of these elements we find broad structures with one or more resonances
superposed on them (see KFK ^52 (1966): Fe at the energies
60 and 135 keV, "cr at 72 and 93 keV). Until now we have not yet
achieved a satisfactory interpretation of these phenomena. In the
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case of ^ Fe we have to check the influence of a possible inelastic
scattering channel for the compound states J = 1 on the shape of
the cross section.
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A further broad structure one can see in -^Cr at 137 keV, but in
contrast to the above mentioned structures we find a resolved re­
sonance with spin 2 at 125 keV which shows a strong interference
effect. The shape of this resonance can be explained only by inter­
ference with an underlying broad resonance of the same spin. The
maximum cross section of the broad structure however corresponds