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Total reaction cross section for ^(12)C + ^(16)O below the Coulomb barrier

Čujec, B. and Barnes, C. A. (1976) Total reaction cross section for ^(12)C + ^(16)O below the Coulomb barrier. Nuclear Physics A, 266 (2). pp. 461-493. ISSN 0375-9474. doi:10.1016/0375-9474(76)90370-5.

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The energy dependence of the total reaction cross section, σ(E), for ^(12)C + ^(16)O has been measured over the range E_(c.m.) = 4–12 MeV, by detecting γ-rays from the various possible residual nuclei with two large NaI(Tl) detectors placed close to the target. This technique for measuring total reaction cross sections was explored in some detail and shown to yield reliable values for σ(E). Although the principal emphasis of this work was placed on obtaining reliable cross sections, a preliminary study has been made of the suitability of various methods for extrapolating the cross section to still lower energies. The statistical model provides a good fit with a reasonable value for the strength function, 〈γ^2〉/〈D〉 = 6.8 × 10^(−2), over the range E_(c.m.) = 6.5–12 MeV, but predicts cross sections which are much too large for E_(c.m.) < 6.5 MeV. Optical model fits at low energies are especially sensitive to the radius and diffuseness of the imaginary component of the potential and, since these are still poorly known at present, such extrapolations may be wrong by orders of magnitude. A simple barrier penetration model gives a moderately good fit to the data and seems to provide the safest extrapolation to lower energies at the present time. It is clear, however, that our knowledge of the heavy-ion reaction mechanism at low energies is incomplete, and that cross-section measurements at still lower energies are needed to establish the correct procedure for extrapolating heavy-ion reaction cross sections to low energies.

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Additional Information:© 1976 North-Holland Publishing Co. Received 11 March 1976. Supported in part by the US National Science Foundation [MPS71-02670 A05] and by the Atomic Energy Control Board of Canada. The authors wish to thank Prof. William A. Fowler for pointing out the need for further study of heavy-ion total reaction cross sections at low energies, and for helpful discussions of the interpretation of such measurements. We are indebted to Drs. Sidney Kahana, Georges Michaud, Aage Winther and Ricardo Broglia for comments on the theoretical interpretation of the data, and to Drs. z. E. Switkowski, R. M. Wieland, R. Dayras and P. R. Christensen for communicating the results of their low-energy heavy-ion experiments. We thank Dr. Peggy L. Dyer, Dr. Hay-Boon Mak and Mr. Thomas R. Greenlee for assistance with some of the measurements, and Mrs. Barbara A. Zimmerman, Mr. George Fox, Mr. Philip Marcus and Mr. Jean-Eudes Villeneuve for assistance with the numerical calculations.
Funding AgencyGrant Number
NSFMPS71-02670 A05
Atomic Energy Control Board (Canada)UNSPECIFIED
Subject Keywords:Nuclear reaction
Issue or Number:2
Record Number:CaltechAUTHORS:20150909-153420526
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Official Citation:B. Čujec, C.A. Barnes, Total reaction cross section for 12C + 16O below the Coulomb barrier, Nuclear Physics A, Volume 266, Issue 2, 9 August 1976, Pages 461-493, ISSN 0375-9474, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:60138
Deposited By: Ruth Sustaita
Deposited On:11 Sep 2015 17:15
Last Modified:10 Nov 2021 22:30

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