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Title: Oscillations above the barrier in the fusion of 28Si + 28Si

Abstract

Fusion cross sections of 28Si+ 28Si have been measured in a range above the barrier with a very small energy step (Delta E lab=0.5 MeV). Regular oscillations have been observed, best evidenced in the first derivative of the energy-weighted excitation function. For the first time, quite different behaviors (the appearance of oscillations and the trend of sub-barrier cross sections) have been reproduced within the same theoretical frame, i.e., the coupled-channel model using the shallow M3Y+repulsion potential. The calculations suggest that channel couplings play an important role in the appearance of the oscillations, and that the simple relation between a peak in the derivative of the energy-weighted cross section and the height of a centrifugal barrier is lost, and so is the interpretation of the second derivative of the excitation function as a barrier distribution for this system, at energies above the Coulomb barrier.

Authors:
 [1];  [2];  [3];  [2];  [4];  [2];  [5];  [4];  [2];  [3];  [1];  [1];  [6];  [1];  [1];  [1];  [1];  [6];  [1]
  1. Dipartimento di Fisica e Astronomia, Università di Padova, and INFN, Padova (Italy)
  2. INFN, Laboratori Nazionali di Legnaro (Italy)
  3. Argonne National Lab., IL (United States)
  4. IPHC, Universite de Strasbourg, Cedex (France)
  5. Institute of Nuclear Physics, Polish Academy of Sciences, Cracow (Poland)
  6. Ruder Boskovic Inst., Zagreb (Croatia)
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26)
OSTI Identifier:
1198151
Alternate Identifier(s):
OSTI ID: 1209101
Grant/Contract Number:
AC02-06CH11357
Resource Type:
Journal Article: Published Article
Journal Name:
Physics Letters. Section B
Additional Journal Information:
Journal Volume: 746; Journal Issue: C; Journal ID: ISSN 0370-2693
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS

Citation Formats

Montagnoli, G., Stefanini, A.M., Esbensen, H., Corradi, L., Courtin, S., Fioretto, E., Grebosz, J., Haas, F., Jia, H.M., Jiang, C.L., Mazzocco, M., Michelagnoli, C., Mijatović, T., Montanari, D., Parascandolo, C., Scarlassara, F., Strano, E., Szilner, S., and Torresi, D. Oscillations above the barrier in the fusion of 28Si + 28Si. United States: N. p., 2015. Web. doi:10.1016/j.physletb.2015.05.021.
Montagnoli, G., Stefanini, A.M., Esbensen, H., Corradi, L., Courtin, S., Fioretto, E., Grebosz, J., Haas, F., Jia, H.M., Jiang, C.L., Mazzocco, M., Michelagnoli, C., Mijatović, T., Montanari, D., Parascandolo, C., Scarlassara, F., Strano, E., Szilner, S., & Torresi, D. Oscillations above the barrier in the fusion of 28Si + 28Si. United States. doi:10.1016/j.physletb.2015.05.021.
Montagnoli, G., Stefanini, A.M., Esbensen, H., Corradi, L., Courtin, S., Fioretto, E., Grebosz, J., Haas, F., Jia, H.M., Jiang, C.L., Mazzocco, M., Michelagnoli, C., Mijatović, T., Montanari, D., Parascandolo, C., Scarlassara, F., Strano, E., Szilner, S., and Torresi, D. Wed . "Oscillations above the barrier in the fusion of 28Si + 28Si". United States. doi:10.1016/j.physletb.2015.05.021.
@article{osti_1198151,
title = {Oscillations above the barrier in the fusion of 28Si + 28Si},
author = {Montagnoli, G. and Stefanini, A.M. and Esbensen, H. and Corradi, L. and Courtin, S. and Fioretto, E. and Grebosz, J. and Haas, F. and Jia, H.M. and Jiang, C.L. and Mazzocco, M. and Michelagnoli, C. and Mijatović, T. and Montanari, D. and Parascandolo, C. and Scarlassara, F. and Strano, E. and Szilner, S. and Torresi, D.},
abstractNote = {Fusion cross sections of 28Si+28Si have been measured in a range above the barrier with a very small energy step (Delta Elab=0.5 MeV). Regular oscillations have been observed, best evidenced in the first derivative of the energy-weighted excitation function. For the first time, quite different behaviors (the appearance of oscillations and the trend of sub-barrier cross sections) have been reproduced within the same theoretical frame, i.e., the coupled-channel model using the shallow M3Y+repulsion potential. The calculations suggest that channel couplings play an important role in the appearance of the oscillations, and that the simple relation between a peak in the derivative of the energy-weighted cross section and the height of a centrifugal barrier is lost, and so is the interpretation of the second derivative of the excitation function as a barrier distribution for this system, at energies above the Coulomb barrier.},
doi = {10.1016/j.physletb.2015.05.021},
journal = {Physics Letters. Section B},
number = C,
volume = 746,
place = {United States},
year = {Wed May 13 00:00:00 EDT 2015},
month = {Wed May 13 00:00:00 EDT 2015}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1016/j.physletb.2015.05.021

Citation Metrics:
Cited by: 5works
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  • Fusion cross sections of 28Si+ 28Si have been measured in a range above the barrier with a very small energy step (Delta E lab=0.5 MeV). Regular oscillations have been observed, best evidenced in the first derivative of the energy-weighted excitation function. For the first time, quite different behaviors (the appearance of oscillations and the trend of sub-barrier cross sections) have been reproduced within the same theoretical frame, i.e., the coupled-channel model using the shallow M3Y+repulsion potential. The calculations suggest that channel couplings play an important role in the appearance of the oscillations, and that the simple relation between a peakmore » in the derivative of the energy-weighted cross section and the height of a centrifugal barrier is lost, and so is the interpretation of the second derivative of the excitation function as a barrier distribution for this system, at energies above the Coulomb barrier.« less
  • Fusion cross sections of Si-28 + Si-28 have been measured in a range above the barrier with a very small energy step (Delta E-lab = 0.5 MeV). Regular oscillations have been observed, best evidenced in the first derivative of the energy-weighted excitation function. For the first time, quite different behaviors (the appearance of oscillations and the trend of sub-barrier cross sections) have been reproduced within the same theoretical frame, i.e., the coupled-channel model using the shallow M3Y + repulsion potential. The calculations suggest that channel couplings play an important role in the appearance of the oscillations, and that the simplemore » relation between a peak in the derivative of the energy-weighted cross section and the height of a centrifugal barrier is lost, and so is the interpretation of the second derivative of the excitation function as a barrier distribution for this system, at energies above the Coulomb barrier.« less
  • Excitation functions for the above-barrier fusion cross sections are measured for the first time for the {sup 7}Li+{sup 28}Si system by two methods--the characteristic {gamma}-ray method and the evaporation {alpha} measurement method--in the energy range E{sub lab}=11.5-26 MeV. Experimental results are consistent and agree with each other, and the one-dimensional Barrier Penetration Model (BPM) predictions describe the data well up to twice the Coulomb barrier, but they overestimate the data by about 15-20% at higher energies.
  • The optical model with a repulsive core and the coupled-channel method are used in analysis of new experimental data on /sup 16/O+/sup 28/Si scattering at large angles in the energy range E = 29--35 MeV. The role of collective excitations of the target nucleus in the mechanism of anomalous scattering of heavy ions is discussed.
  • We have measured the fusion excitation function and {gamma}-ray multiplicities {ital M}{sub {gamma}} for the {sup 28}Si+{sup 154}Sm system. We have also measured {ital M}{sub {gamma}} for the {sup 16}O+{sup 166}Er system that leads to the same compound nucleus, {sup 182}Os, as a calibration of the connection between {ital M}{sub {gamma}} and the first moment of the spin distribution, {l angle}{ital l}{r angle}. We find that the deduced {l angle}{ital l}{r angle} for {sup 28}Si+{sup 154}Sm agrees reasonably well with theoretical calculations, and in particular its energy dependence exhibits the barrier bump expected when a shape degree of freedom ismore » strongly coupled to the relative motion.« less