1 - IAEA Nuclear Data Services

- 75 -
In collaboration with the Trieste Group we have in course
measurements o£ neutron spectra, aiming at levels spectrometry,
and at a search of analogue states as resonances of compound
nucleus.
2.1 . (n,2n) reactions on 8o Br, 91 Mo, 112 In, 143 Sm
The cross-section ratios for the production of the isomeric
pairs 80m »£Br, 91m,gMo, 112m »9ln, 143m,gSm through the (n,2n)
reaction have been measured by the activation method. The
experimental data of this activity and those available from
the literature have been analysed by the Huizenga-Vandenbosch
method, and the spin cutoff parameter has been extracted.
3.1. 1 ^0 (n,g) 1 ^C reaction (in collaboration with the Bologna Group)
About 5000 two prong events produced by 14 MeV neutrons in a
Wilson chamber Oxygen filled were observed and measured. About
70% of these events is attributable to 1 °0 (n,a) 1 ^C reactions.
The attribution was made by a suitable cinematical fit. Each
event was also checked for (n,p) and (n,d) reactions, both
energically possible.
The range-energy relation for 1 ^C in Oxygen has been obtained
in good agreement with that found in a previous experiment for
1 3c in Neon.
The spectrum of the excitation energy shows, well separated,
the fundamental and first excited level of ^C. The second
and third ones, on the contrary, are not resolved. The angular
distributions for all the events and for distinct levels have
1 7
been constructed.^- particles show, in the rest frame of 0, a
well definite peak in the backward direction, for fundamental
and first excited level. This behaviour suggests that also
for 16 0(n,a) 1 ^C reactions direct interactions such as heavy
stripping mechanism are present.
This result is in very good agreement with previous experiments