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Title: {sup 12}C({alpha},{gamma}){sup 16}O E2 cross section: R-matrix fits combined with a microscopic cluster model

Abstract

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 notmore » 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.« less

Authors:
 [1];  [2]
  1. IPHC Bat27, IN2P3-CNRS/Universite Louis Pasteur BP28, F-67037 Strasbourg Cedex 2 (France)
  2. Physique Nucleaire Theorique et Physique Mathematique, C.P. 229, Universite Libre de Bruxelles (ULB), B-1050 Brussels (Belgium)
Publication Date:
OSTI Identifier:
21192073
Resource Type:
Journal Article
Journal Name:
Physical Review. C, Nuclear Physics
Additional Journal Information:
Journal Volume: 78; Journal Issue: 1; Other Information: DOI: 10.1103/PhysRevC.78.015808; (c) 2008 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0556-2813
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; ALPHA PARTICLES; ASYMPTOTIC SOLUTIONS; CAPTURE; CARBON 12 TARGET; CLUSTER MODEL; CROSS SECTIONS; E2-TRANSITIONS; EXCITED STATES; GAMMA DECAY; GENERATOR-COORDINATE METHOD; GROUND STATES; KEV RANGE; NUCLEON-NUCLEON INTERACTIONS; OXYGEN 16; PHASE SHIFT; R MATRIX; SIMULATION

Citation Formats

Dufour, M, and Descouvemont, P. {sup 12}C({alpha},{gamma}){sup 16}O E2 cross section: R-matrix fits combined with a microscopic cluster model. United States: N. p., 2008. Web. doi:10.1103/PHYSREVC.78.015808.
Dufour, M, & Descouvemont, P. {sup 12}C({alpha},{gamma}){sup 16}O E2 cross section: R-matrix fits combined with a microscopic cluster model. United States. https://doi.org/10.1103/PHYSREVC.78.015808
Dufour, M, and Descouvemont, P. Tue . "{sup 12}C({alpha},{gamma}){sup 16}O E2 cross section: R-matrix fits combined with a microscopic cluster model". United States. https://doi.org/10.1103/PHYSREVC.78.015808.
@article{osti_21192073,
title = {{sup 12}C({alpha},{gamma}){sup 16}O E2 cross section: R-matrix fits combined with a microscopic cluster model},
author = {Dufour, M and Descouvemont, P},
abstractNote = {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.},
doi = {10.1103/PHYSREVC.78.015808},
url = {https://www.osti.gov/biblio/21192073}, journal = {Physical Review. C, Nuclear Physics},
issn = {0556-2813},
number = 1,
volume = 78,
place = {United States},
year = {2008},
month = {7}
}