{sup 12}C({alpha},{gamma}){sup 16}O E2 cross section: R-matrix fits combined with a microscopic cluster model
- IPHC Bat27, IN2P3-CNRS/Universite Louis Pasteur BP28, F-67037 Strasbourg Cedex 2 (France)
- Physique Nucleaire Theorique et Physique Mathematique, C.P. 229, Universite Libre de Bruxelles (ULB), B-1050 Brussels (Belgium)
The E2 component of the {sup 12}C({alpha},{gamma}){sup 16}O cross section is investigated in two ways: by a microscopic cluster model, and by R-matrix fits. The {alpha}+{sup 12}C microscopic calculation is performed in the framework of the generator coordinate method (GCM) by including all {sup 12}C states (T=0) within the p shell. Using different nucleon-nucleon interactions we find S{sub E2}(300 keV){approx_equal}50 keV {center_dot} b for ground-state transitions. We also study cascade transitions to the 0{sub 2}{sup +} and 2{sub 1}{sup +} excited states of {sup 16}O. Then the S-factor is analyzed in the phenomenological R-matrix theory. We show that the background term plays a crucial role, and cannot be determined without ambiguity. Using the experimental phase shifts and capture cross sections, only an upper limit on the extrapolated S factor can be obtained [S{sub E2}(300 keV)<190 keV {center_dot} b]. To constrain the R-matrix analysis, we use the GCM asymptotic normalization constant (ANC) of the 2{sub 1}{sup +} level, well known to be a cluster state. This procedure strongly reduces the uncertainties on the R-matrix fit, and we end up with a recommended value of S{sub E2}(300 keV)=42{+-}2 keV {center_dot} b. We show that ANC values derived from indirect methods are not consistent with the {sup 12}C({alpha},{gamma}){sup 16}O cascade transitions to the 2{sub 1}{sup +} state, and suggest that a remeasurement of this cross section is desirable.
- OSTI ID:
- 21192073
- Journal Information:
- Physical Review. C, Nuclear Physics, Vol. 78, Issue 1; Other Information: DOI: 10.1103/PhysRevC.78.015808; (c) 2008 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 0556-2813
- Country of Publication:
- United States
- Language:
- English
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