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Title: Fusion hindrance and quasi-fission in heavy-ion induced reactions: disentangling the effect of different parameters

Abstract

Experimental results on the fusion inhibition effect near the Coulomb barrier due to the onset of the quasi-fission mechanism are presented. The investigation was focused on reactions induced by 48Ca projectiles on different heavy targets and comparing them to reactions induced by light ions such as 12C and 16O leading to the same compound nuclei. Cross sections and angular distributions of evaporation residues and fission fragments have been measured.

Authors:
; ; ; ; ;  [1];  [2];  [3]; ; ;  [4];  [3]; ; ; ; ; ; ; ; more »;  [5];  [6] « less
  1. INFN Laboratori Nazionali di Legnaro, Legnaro, Padova (Italy)
  2. Dipartimento di Fisica, Naples (Italy)
  3. (Italy)
  4. Dipartimento di Fisica, Padova (Italy)
  5. Flerov Laboratory of Nuclear Reactions, JINR, Dubna (Russian Federation)
  6. IReS, IN2P3-CNRS/UPL, Strasbourg Cedex 2 (France) (and others)
Publication Date:
OSTI Identifier:
20798559
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 831; Journal Issue: 1; Conference: International conference on frontiers in nuclear structure, astrophysics, and reactions - FINUSTAR, Isle of Kos (Greece), 12-17 Sep 2005; Other Information: DOI: 10.1063/1.2200950; (c) 2006 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; ANGULAR DISTRIBUTION; CALCIUM 48; CARBON 12; COMPOUND NUCLEI; COULOMB FIELD; CROSS SECTIONS; EVAPORATION MODEL; FISSION; FISSION FRAGMENTS; HEAVY ION FUSION REACTIONS; HEAVY IONS; OXYGEN 16; QUASI-FISSION

Citation Formats

Fioretto, E., Stefanini, A. M., Behera, B. R., Corradi, L., Gadea, A., Latina, A., Trotta, M., INFN Sezione di Napoli, Naples, Beghini, S., Montagnoli, G., Scarlassara, F., INFN Sezione di Padova, Padova, Chizhov, A. Yu., Itkis, I. M., Itkis, M. G., Kniajeva, G. N., Kondratiev, N. A., Kozulin, E. M., Pokrovsky, I. V., Sagaidak, R. N., Voskressensky, V. M., and Courtin, S. Fusion hindrance and quasi-fission in heavy-ion induced reactions: disentangling the effect of different parameters. United States: N. p., 2006. Web. doi:10.1063/1.2200950.
Fioretto, E., Stefanini, A. M., Behera, B. R., Corradi, L., Gadea, A., Latina, A., Trotta, M., INFN Sezione di Napoli, Naples, Beghini, S., Montagnoli, G., Scarlassara, F., INFN Sezione di Padova, Padova, Chizhov, A. Yu., Itkis, I. M., Itkis, M. G., Kniajeva, G. N., Kondratiev, N. A., Kozulin, E. M., Pokrovsky, I. V., Sagaidak, R. N., Voskressensky, V. M., & Courtin, S. Fusion hindrance and quasi-fission in heavy-ion induced reactions: disentangling the effect of different parameters. United States. doi:10.1063/1.2200950.
Fioretto, E., Stefanini, A. M., Behera, B. R., Corradi, L., Gadea, A., Latina, A., Trotta, M., INFN Sezione di Napoli, Naples, Beghini, S., Montagnoli, G., Scarlassara, F., INFN Sezione di Padova, Padova, Chizhov, A. Yu., Itkis, I. M., Itkis, M. G., Kniajeva, G. N., Kondratiev, N. A., Kozulin, E. M., Pokrovsky, I. V., Sagaidak, R. N., Voskressensky, V. M., and Courtin, S. Wed . "Fusion hindrance and quasi-fission in heavy-ion induced reactions: disentangling the effect of different parameters". United States. doi:10.1063/1.2200950.
@article{osti_20798559,
title = {Fusion hindrance and quasi-fission in heavy-ion induced reactions: disentangling the effect of different parameters},
author = {Fioretto, E. and Stefanini, A. M. and Behera, B. R. and Corradi, L. and Gadea, A. and Latina, A. and Trotta, M. and INFN Sezione di Napoli, Naples and Beghini, S. and Montagnoli, G. and Scarlassara, F. and INFN Sezione di Padova, Padova and Chizhov, A. Yu. and Itkis, I. M. and Itkis, M. G. and Kniajeva, G. N. and Kondratiev, N. A. and Kozulin, E. M. and Pokrovsky, I. V. and Sagaidak, R. N. and Voskressensky, V. M. and Courtin, S.},
abstractNote = {Experimental results on the fusion inhibition effect near the Coulomb barrier due to the onset of the quasi-fission mechanism are presented. The investigation was focused on reactions induced by 48Ca projectiles on different heavy targets and comparing them to reactions induced by light ions such as 12C and 16O leading to the same compound nuclei. Cross sections and angular distributions of evaporation residues and fission fragments have been measured.},
doi = {10.1063/1.2200950},
journal = {AIP Conference Proceedings},
number = 1,
volume = 831,
place = {United States},
year = {Wed Apr 26 00:00:00 EDT 2006},
month = {Wed Apr 26 00:00:00 EDT 2006}
}
  • It is shown that with the inclusion of fission following incomplete fusion in addition to the normal equilibrium fission following compound nucleus formation and the recently proposed pre-equilibrium fission, one can understand in a quantitative way the host of apparently anomalous fragment angular distributions measured in a number of heavy ion induced fission reactions involving the highly fissile actinides as one of the collision partners.
  • In order to describe the fusion of heavy ions we classify the existing models and formulate a new model of the process. The model predicts three regions in the energy dependence of the fusion cross section. The results of calculations are compared with the experimental data. A particular emphasis is given to the discussion of fusion of very heavy nuclei. We explain the differences in product yields of the reactions /sup 84/Kr+/sup 186/W and /sup 40/Ar+/sup 238/U, which lead to similar composite systems. These differences are understood without introduction of the ''l-window'' hypothesis.
  • It has been found that the fraction of the reaction cross section diverted to complete fusion of light heavy ions is strongly correlated to the nucleon (cluster) separation energy of the participants. The presence of weakly bound nuclei hinder the fusion cross section indicating that they do not survive the collision long enough in order to contribute significantly to the fusion process. Model calculations support this picture. The {sup 38}Ar compound nucleus populated by entrance channels with different mass asymmetries, i.e., {sup 9}Be+{sup 29}Si, {sup 11}B+{sup 27}Al, {sup 12}C+{sup 26}Mg, and {sup 19}F+{sup 19}F, has been investigated, supporting the mentionedmore » correlation. Consequence of this effect in the fusion cross section of exotic nuclei is discussed.« less
  • The {alpha}-particle energy spectra have been measured in coincidence with fission fragments over a wide range of relative angles with respect to fragment emission direction in the {sup 11}B (62 MeV) + {sup 232}Th reaction. The {alpha}-particle multiplicity spectra have been fitted with moving source model to extract the precision ({alpha}{sub pre}) and near-scission ({alpha}{sub nse}) components. The present results, along with available data from the literature over a wide range of Z{sup 2}/A and the excitation energy of a compound system, have been analyzed to develop certain global features of the pre- and near-scission emission characteristics. It is seenmore » that {alpha}{sub pre} values when normalized to E{sub CN}{sup 2.3} (E{sub CN} is the compound nucleus excitation energy) show a systematic linearly increasing trend with the {alpha}-particle emission Q value (Q{sub {alpha}}). The fraction of near-scission multiplicity is observed to be nearly the same at around 10% of the total precision multiplicity for all the systems.« less