1 - IAEA Nuclear Data Services
1 - IAEA Nuclear Data Services
1 - IAEA Nuclear Data Services
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been studied from the theoretical point o£ view, in order to<br />
have a support for the hypothesis underlying the method of<br />
spin assignment. A numerical simulation of the process has<br />
been performed, exploiting existing experimental data on the<br />
low-excitation levels and the theories for the level density<br />
of higher excitation energy, and for transition probabilities<br />
of the different multipolarities. Particular care has been<br />
devoted to the influence of the limitations in the detecting<br />
apparatus, such as the varying efficiency of Nal crystals as<br />
a function of the energy, and the effect of the energy thresh<br />
olds which are artificially set to the gamma detection. In<br />
this way the result of the comparison between computation and<br />
experiment depends only on the consistency of the model used<br />
with the real nuclear process. The calculation gives results<br />
which are directly comparable with experiments related to the<br />
Y-decay from neutron capture states. The experiment of spin<br />
assignment involves some integral features of the y-decay,<br />
such as mean multiplicity and the integral of the y-spectrum<br />
above a given energy. In this respect the model works well,<br />
the accordance with the experiment being satisfactory. A more<br />
crucial test would be a systematic comparison with measurements<br />
of the detailed shape of the y-energy spectra. The comparison<br />
performed in the particular case of 1 77nf has shown a good<br />
accordance, but has also indicated some deficiencies of the<br />
model, when low-lying levels are involved. Such deficiencies<br />
can be explained with the general uncertainties of the theory.<br />
The results of the calculation can also be compared with other<br />
possible experiments, such as absolute multiplicity of isomeric<br />
cross section ratio measurements.