Abstract
It is proposed to renormalize the exciton-state densities used in models for precompound decay such that the summed state densities agree with the expressions employed in equilibrium statistical models. In this way a close fit can be guaranteed between preequilibrium model calculations and the results of equilibrium statistical models for the evaporative stage of the reaction. The consequences of this proposal for the internal transition rates of the pre-equilibrium exciton model are analyzed. The matrix element for the residual interaction is obtained not from a phenomenological parametrization, but from the nucleon mean free path in nuclear matter. It is demonstrated that the proposed renormalization, from one-component Fermi-gas formulas to two-fermion expressions for the state densities, leads to strongly improved agreement of the effective exciton-model values for the nucleon mean free path in nuclear matter with realistic estimates. It is proved that the particle-hole state densities for a two-component Fermi gas, summed over the allowed exciton-state numbers, agree with the phenomenological state-density expressions used in statistical Hauser-Feshbach models.
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References
Blann, M.: Annu. Rev. Nucl. Sci.25, 123 (1975)
Ericson, T.: Adv. Phys.9, 425 (1960)
Williams, F.C., Jr.: Phys. Lett.31 B, 184 (1970)
Dobes, J., Betàk, E.: Z. Phys. A — Atoms and Nuclei310, 329 (1983)
Gupta, S.K.: Z. Phys. A — Atoms and Nuclei303, 329 (1981)
Kalbach-Cline, C.: Nucl. Phys.A210, 590 (1973)
Kalbach, C.: Z. Phys. A — Atoms and Nuclei287, 319 (1978)
Blann, M.: Phys. Rev. Lett.27, 337, 700(E), 1550(E) (1971)
Gilbert, A., Cameron, A.G.W.: Can. J. Phys.43, 1446 (1965)
Dilg, W., Schantl, W., Vonach, H., Uhl, M.: Nucl. Phys. A217, 269 (1973)
Costa, C., Gruppelaar, H., Nierop, D., Akkermans, J.M.: Proc. Int. Conf. on Nuclear Data for Science and Technology. (Antwerp, September 1982) Böckhoff, K.H., (ed.), p. 537. Dordrecht: D. Reidel Publ. Co. 1983
Gruppelaar, H.: IAEA Advisory Group Meeting on Basic and Applied Problems of Nuclear Level Densities. Bhat, M.R. (ed.), Report BNL-NCS-51694, p. 143. New York: Brookhaven National Laboratory 1983
Kalbach, C.: Z. Phys. A — Atoms and Nuclei283, 401 (1977)
Cline, C.K.: Nucl. Phys.A193, 417 (1972)
Williams, F.C., Jr.: Phys. Lett.31B, 184 (1970)
Oblozinský, P., Ribansky, I., Bětàk, E.: Nucl. Phys. A226, 347 (1974)
Gadioli, E., Gadioli Erba, E., Sona, P.G.: Nucl. Phys. A217, 589 (1973)
Machner, H.: Z. Phys. A — Atoms and Nuclei302, 125 (1981)
Kikuchi, K., Kawai, M.: Nuclear Matter and Nuclear Reactions. Amsterdam: North-Holland Publ. Co. 1968
Abramowitz, M., Stegun, I.A. (Eds.): Handbook of Mathematical Functions, p. 257. New York: Dover Publications Inc. 1965
Gruppelaar, H., Akkermans, J.M.: The GRAPE Code System for the Calculation of Precompound and Compound Nuclear Reactions: GRYPHON Code Description and User's Manual, ECN-164. Petten (N-H): Netherlands Energy Research Foundation Report (1985)
Gadioli, E., Gadioli Erba, E.: Phys. Rev. C17, 2238 (1978)
Blann, M.: Phys. Rev. C27, 1871 (1978)
Blann, M.: Phys. Rev. Lett.28, 757 (1972)
Blann, M.: Phys. Rev. C23, 205 (1981)
Akkermans, J.M.: The Pre-Equilibrium Hybrid and Exciton Models Revisited, Contr. to Inf. Conf. on Nuclear Data for Basic and Applied Science, May 1985, Santa Fe, NM.
Takahashi, A., Yamamoto, J., Murakami, T., Oshima, K., Oda, H., Fujimoto, K., Ueda, M., Fukazawa, M., Yanagi, Y., Miyaguchi, J., Sumita, K.: Double-Differential Neutron Emission Cross-Sections, Numerical Tables and Figures, Oktavian Report A-83-01. Osaka University: 1983
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Akkermans, J.M., Gruppelaar, H. Comments on the state densities and the transition rates in the pre-equilibrium exciton model. Z Physik A 321, 605–612 (1985). https://doi.org/10.1007/BF01432437
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DOI: https://doi.org/10.1007/BF01432437