Summary
Measurements of the energy spectra of protons emitted in n, p and n, np reactions with 14 MeV neutrons are described. The spectra are taken at four different angles in the case of Ni, Cu, Mo, and Ag. The results are compared with other results in the domain of the nuclear reactions at intermediate energy. The mechanisms responsible for the various reactions can be shortly indicated: 1) instantaneous effects: the forward emitted high energy particles are due to such effects. 2) non equilibrium escape is responsible for the main part of the spectra and for emission at any angle. The escape is supposed to be due to the strong interactions between few excited nucleons at the nuclear surface; 3) retarded emission, probably after stabilized equilibrium is reached, will explain the emission of protons by mediumA nuclei and of neutrons when incident energy is below 18 MeV. Values of temperatures of ∼ 1 MeV are found. In n, 2n and n, np reactions strong emission of protons competes in some cases with neutron emissions. The role of surface conditions in this retarded emission is enlightened.
Riassunto
Vengono descritte misure dello spettro energetico di protoni emessi in relazioni n,p ed n, np prodotte da neutroni di 14 MeV per Ni, Cu, Mo ed Ag. Lo spettro è misurato a quattro angoli per ciascuno di questi casi. I risultati ottenuti vengono confrontati con altri risultati noti di spettri di particelle emesse in reazioni nucleari alle medie energie. I meccanismi che intervengono in queste reazioni possono così riassumersi: 1) effetti istantanei responsabili dell’emissione delle particelle a più alta energia ed emesse soprattutto ad angoli in avanti. 2) fuga di non equilibrio relativa alle particelle delle parti medie dello spettro ed emesse a tutti gli angoli. Viene discussa la possibilità di tali processi di fuga in connessione con le interazioni fra nucleoni eccitati alla superficie del nucleo. 3) emissione ritardata, probabilmente successiva ad un equilibrio statistico, responsabile della emissione di protoni in nuclei medi e di neutroni per energie incidenti non superiori a 18 MeV. Temperature di ∼ 1 MeV vengono confermate. In reazioni n, np od n, 2n vengono osservate in alcuni casi probabilità di emissione maggiori per protoni che per neutroni. Una discussione di queste emissioni porta a fare l’ipotesi che gli elementi di matrice delle varie reazioni risentano fortemente delle condizioni della superficie nucleare.
Similar content being viewed by others
References
D. C. Peaslee:Ann. Rev. Nucl. Sci.,5, 99 (1955).
R. M. Eisberg, G. Igo andH. E. Wegner:Phys. Rev.,100, 1309 (1955).
B. L. Cohen andA. G. Rubin: to be published.
N. O. Lassen andN. O. Roy Pulsen:International Conference on Low Energy Nuclear Physics in Paris (July 1958).
I. Kumabe, E. Takekoshi, H. Ogata, Y. Tsuneoka andS. Oki:Phys. Rev.,106, 155 (1957).
L. Rosen andL. Stewart:Phys. Rev.,107, 824 (1957).
S. H. Ahn andJ. H. Roberts:Phys. Rev.,108, 110 (1957).
D. L. Allan:Proc. Phys. Soc., A70, 195 (1957).
G. Brown, G. C. Morrison, H. Muirhead andW. T. Morton:Phil. Mag.,2, 785 (1957).
P. V. March andW. T. Morton:Phil. Mag.,3, 143 (1958).
P. V. March andW. T. Morton:Phil. Mag.,3, 577 (1958).
Handb. d. Phys., Nuclear Reactions I,40, 202 and foll.
J. Benveniste:International Conference of Geneva, P/2494 (1958).
G. Brown andH. Muirhead:Phil. Mag.,2, 473 (1957).
G. Igo andH. E. Wegner:Phys. Rev.,102, 1364 (1956).
See for instance:C. T. De Dominicis:International Conference on Low Energy Nuclear Physics in Paris (July 1958) andJourn. Phys. Rad.,19, 1 (1958).
C. Badoni, L. Colli andU. Facchini:Nuovo Cimento,4, 1618 (1956).
L. Colli andU. Facchini:Nuovo Cimento,5, 309 (1957).
L. Colli, U. Facchini, I. Iori, G. Marcazzan, A. M. Sona andM. Pignanelli:Nuovo Cimento,7, 400 (1958).
L. Colli, M. Pignanelli, A. Rytz andR. Zurmühle:Nuovo Cimento,9, 280 (1958).
G. Marcazzan, M. Pignanelli andA. Sona:Nuovo Cimento,10, 155 (1958).
L. Colli, F. Cvelbar, S. Micheletti andM. Pignanelli: to be published.
D. L. Allan:Nucl. Phys.,6, 464 (1958).
V. F. Weisskopf:Proc. of the International Conference on Nuclear Reactions (Amsterdam, 1956).
G. E. Brown andC. T. De Dominicis:Proc. Phys. Soc., A70, 668 (1957).
G. E. Brown andC. T. De Dominicis:Proc. Phys. Soc., A72, 70 (1958).
F. Friedman andV. Weisskopf:Niels Bohr and the development of Physics (London, 1955).
V. F. Weisskopf:Geneva Conference (Sept. 1958), discussion in Sect. A 19.
Handb. d. Phys.,40, 212.
V. F. Weisskopf andD. H. Ewing:Phys. Rev.,57, 472 (1940).
P. C. Gugelot:Phys. Rev.,93, 425 (1954).
G. Igo:Phys. Rev.,106, 256 (1957).
R. M. Eisberg andG. Igo:Phys. Rev.,93, 1039 (1954).
B. L. Cohen:Phys. Rev.,105, 1549 (1957).
B. L. Cohen:Phys. Rev., in print.
J. S. Levinger:Int. Conf. on Low Energy Nuclear Physics (Paris, July 1958).
J. M. C. Scott:Phil. Mag.,45, 441 (1954).
J. A. Evans:Proc. Phys. Soc.,73, 33 (1959).
K. Kikuchi:Progr. Theor. Phys.,17, 643 (1957).
J. Nemeth:Nucl. Phys.,6, 686 (1958).
A. M. Lane:Discussion at Int. Conf. on Low Energy Nuclear Physics (Paris, July 1958).
B. L. Cohen:Int. Conf. on Low Energy Nuclear Physics (Paris, July 1958).
E. R. Graves andL. Rosen:Phys. Rev.,89, 343 (1953).
R. Britten:Phys. Rev.,88, 283 (1952).
H. Feshbach, M. M. Shapiro andV. F. Weisskopf: NYO-3077 (1954).
L. Colli, U. Facchini andS. Micheletti:Nuovo Cimento,5, 502 (1957).
D. L. Allan: Private Communication on54Fe (n, p).
T. Ericson: Private Communication byA. M. Lane.
See the papers of the ONR group at MIT in 1957–1958.
E. B. Paul andR. L. Clarke:Can. Journ. Phys.,31, 267 (1953).
Handb. d. Phys., Nuclear Reactions I,40, 251.
P. C. Gugelot inNuclear Reactions, (Amsterdam, 1959).
Handb. d. Phys. Nuclear Reactions I,40, 218 and 255.
H. G. Blosser, C. D. Goodman andT. H. Handley:Phys. Rev.,110, 521 (1958).
J. L. Perkin, L. P. O’Connor andE. F. Coleman:Proc. Phys. Soc.,72, 505 (1958).
R. F. Coleman, B. E. Hawker, L. P. O’Connor andJ. L. Perkin:Proc. Phys. Soc.,73, 215 (1959).
C. A. Levinson andM. K. Banerjee:Ann. Phys.,2, 471, 499 (1957) and3, 67 (1958).
J. Sawicki: NYO-8084 (1958).
Handb. d. Phys., Nuclear Reactions I,40, 143.
A. M. Lane:Discussion at International Conf. on Low Energy Nuclear Physics (Paris, July 1958).
N. Austern, S. T. Butler andH. McManus:Phys. Rev.,92, 350 (1953).
S. Hayakawa, M. Kawai andK. Kikuchi:Progr. Theor. Phys.,13, 415 (1955).
L. B. B. Elton andL. C. Gomes:Phys. Rev.,105, 1027 (1957).
S. T. Butler:Phys. Rev.,106, 272 (1956).
K. A. Brueckner:Phys. Rev.,103, 172 (1956).
F. Bjorklund andS. Fernbach:Geneva Conf., P/649 (Sept. 1958).
V. N. Levkovskji:Sov. Phys. Journ. Exp. Phys. Theor.,6, 1174 (1958).
P. C. Gugelot:Phys. Rev.,81, 51 (1951).
We recall that we are considering the backward angles. In fact in the forward direction different behaviours for various nuclei and the appearance of well defined excited states of residual nuclei has been evidenced recently in n, p reactions (22).
L. E. Trainor, W. R. Dixon:Can. Journ. of Phys.,34, 229 (1956).
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Colli, L., Facchini, U., Iori, I. et al. n, p and n, np reactions with 14 MeV neutrons. Nuovo Cim 13, 730–760 (1959). https://doi.org/10.1007/BF02726362
Received:
Published:
Issue Date:
DOI: https://doi.org/10.1007/BF02726362