1 - IAEA Nuclear Data Services
1 - IAEA Nuclear Data Services
1 - IAEA Nuclear Data Services
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- 104 -<br />
happens for Th and U at the same energy does not necessarily-<br />
mean that the (y»n) thresholds for the two nuclei coincide.<br />
The position of the minimum may depend in fact on the behaviour<br />
and absolute value of the two cross-sections; with respect to<br />
Uranium, Thorium has actually a much less photofission cross-<br />
-section, while his ( y,n) cross-section grows very sharply [l6J.<br />
The ratio a TV/ a u i- s reported in fig. 3 as a function of energy.<br />
Disregarding the first point because of the large error it is<br />
affected by, this ratio shows a broad maximum at about 7 MeV<br />
which agrees with the Huizenga et al. results [_16J and which<br />
is explained by these authors in terms of the competitivity of<br />
(Y»n) reactions with fission, together with the different thesh-<br />
olds of Uranium and Thorium (y,n) reactions.<br />
References<br />
[l 1 H.G. De Carvalho, A. Manfredini, M. Muchnik, M. Severi,<br />
R. Bosch, J. Lang, R. Muller, W. wfilfli - N. Cim. 25<br />
(1962) 534.<br />
[2 1 H.G. De Carvalho A. Manfredini, M. Muchnik, M. Severi,<br />
R. Bosch, W. Wolfli - N. Cim. £9 (1963) 463.<br />
Ï3 ] A. Manfredini, M. Muchnik, L. Fiore, C. Ramorino, H.G. De<br />
Carvalho, J. Lang, R. Muller - Nucl. Phys. 74 (1965) 377.<br />
[4 "] A. Manfredini, M. Muchnik, L. Fiore, C. Ramorino, H.G. De<br />
Carvalho, R. Bosch, V. Wolfli - N. Cim. 44B (1966) 218.<br />
[6 ] A. Bohr - Int. Conf. on the Peaceful Uses of Atomic Energy<br />
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[7] I. Halpern - Annual Revue of Nucl. Sci. 9 (1956) 245.<br />
[8]T. Kivikas, B. Forkman - Nucl. Phys. 64 (1965) 420.<br />
[9]D.L. Hill, J.A. Wheeler - Phys. Rev. 89 (1953) 1102.<br />
MO J H.G. De Carvalho, A. Manfredini, M. Muchnik, M. Severi,<br />
H. Bosch, J. Lang, R. MÜller, W. Wolfli - N. Cim. 2j><br />
^ (1962) 534.<br />
£11 J A. Manfredini, M. Muchnik, L. Fiore, C. Ramorino, H.G. De<br />
Crvalho, J. Lang, R. Muller - Nucl» Phys. 74 (1965) 377.