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Title: Heavy ion fusion reactions and the nucleus-nucleus potential

Abstract

Several open questions on heavy-ion fusion reactions will be discussed by using a semi-classical model that incorporates well known properties of the interacting nuclei like single particle levels and surface vibrations. It will be shown that the behavior of the fusion excitation function at very low energies is sensitive to the actual shape of the ion-ion potential at distances shorter than the position of the Coulomb barrier and that the high energy hindrance to fusion may be reconciled by taking into account the flux that will remain in all binary reactions.

Authors:
 [1];  [2]
  1. Dipartimento di Fisica Teorica, Universita di Torino, Via Pietro Giuria 1, I-10125 Turin (Italy)
  2. (Italy)
Publication Date:
OSTI Identifier:
20798554
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: 10.1063/1.2200946; (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; COULOMB FIELD; DISTANCE; EXCITATION FUNCTIONS; HEAVY ION FUSION REACTIONS; NUCLEON-NUCLEON POTENTIAL

Citation Formats

Pollarolo, G., and Istituto Nazionale di Fisica Nucleare, Sezione di Torino, Via Pietro Giuria 1, I-10125 Turin. Heavy ion fusion reactions and the nucleus-nucleus potential. United States: N. p., 2006. Web. doi:10.1063/1.2200946.
Pollarolo, G., & Istituto Nazionale di Fisica Nucleare, Sezione di Torino, Via Pietro Giuria 1, I-10125 Turin. Heavy ion fusion reactions and the nucleus-nucleus potential. United States. doi:10.1063/1.2200946.
Pollarolo, G., and Istituto Nazionale di Fisica Nucleare, Sezione di Torino, Via Pietro Giuria 1, I-10125 Turin. Wed . "Heavy ion fusion reactions and the nucleus-nucleus potential". United States. doi:10.1063/1.2200946.
@article{osti_20798554,
title = {Heavy ion fusion reactions and the nucleus-nucleus potential},
author = {Pollarolo, G. and Istituto Nazionale di Fisica Nucleare, Sezione di Torino, Via Pietro Giuria 1, I-10125 Turin},
abstractNote = {Several open questions on heavy-ion fusion reactions will be discussed by using a semi-classical model that incorporates well known properties of the interacting nuclei like single particle levels and surface vibrations. It will be shown that the behavior of the fusion excitation function at very low energies is sensitive to the actual shape of the ion-ion potential at distances shorter than the position of the Coulomb barrier and that the high energy hindrance to fusion may be reconciled by taking into account the flux that will remain in all binary reactions.},
doi = {10.1063/1.2200946},
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}
}
  • We discuss quantum effects in the diffusion process which is used to describe the shape evolution from the touching configuration of fusing two nuclei to a compound nucleus. Applying the theory with quantum effects to the case where the potential field, the mass and friction parameters are adapted to realistic values of heavy-ion collisions, we show that the quantum effects play significant roles at low temperatures which are relevant to the synthesis of superheavy elements.
  • We discuss quantum effects in the diffusion process which is used to describe the shape evolution from the touching configuration of fusing two nuclei to a compound nucleus. Applying the theory with quantum effects to the case where the potential field, the mass and the friction parameters are adapted to realistic values of heavy-ion collisions, we show that the quantum effects play significant roles at low temperatures which are relevant to the synthesis of superheavy elements. We also discuss the mass distribution of the quasi-fission fragments calculated in the two-dimensional quantum Langevin approach.
  • The alpha-particle spectra and the proton spectra at different laboratory angles from the fusion reactions {sup 16}O+{sup 64}Zn at 95 Mev and {sup 32}S+{sup 48}Ti at 125 MeV were measured. Both systems have zero channel spin and lead to the compound nucleus {sup 80}Sr{sup *} with the same value of l{sub max}=43({Dirac_h}/2{pi}). The observed spectra from the asymmetric reaction {sup 16}O+{sup 64}Zn reaction can be reproduced with the statistical model calculations using rotating liquid drop model values of moment of inertia and transmission coefficients for spherical nuclei. However, the charged particle spectra in case of the symmetric {sup 32}S+{sup 48}Timore » reaction are not in agreement with the predictions of the statistical model. In order to explain the experimental spectra for the {sup 32}S+{sup 48}Ti reaction, the analysis was done using the dynamical model of Feldmeier et al. [Rep. Prog. Phys. 50, 915 (1987)]. This analysis shows that the effective l{sub max} value for fusion to take place in the case of the symmetric system is lowered to 30({Dirac_h}/2{pi}). The statistical model calculations for the dynamical model predicted the l{sub max} value reproduced the observed spectra reasonably well indicating entrance channel effects on the decay of the compound nucleus.« less
  • The fusion cross sections for the /sup 16/O+ /sup 152/Sm system in the near- and sub-barrier region are calculated on the basis of a direct reaction description for fusion by introducing a dynamic polarization potential which reproduces coupled-channels effects in a one-channel optical model. It is found that this method explains data as well as coupled-channels results very well. The calculated spin distributions of the compound nucleus again agree well with those from coupled-channels calculations.
  • A broad range of heavy-ion-induced fusion excitation functions are classically analyzed. The fusion-barrier parameters are compared with predictions of the proximity potential, a Yukawa-plus-exponential model, and a modified Woods-Saxon potential. The Yukawa-plus-exponential model is found to give the best overall agreement with the data. The proximity potential is too shallow, but would be in closer agreement with data if a necking contribution were added.