Level Assignments inO17fromC13(α

Abstract

C 13 («,a)C 13 cross sections at center-of-mass angles 54.7°, 107.9°, 142.6°, and 169.6° and C 13 (a,#)0 16 cross sections at 0° have been measured at a-particle energies from 2 to 3.5 MeV. From dispersion-theory analysis, a consistent set of J* and partial-width values has been obtained for eleven states of the compound nucleus O 17 with excitation energies between 8 and 9 MeV. I. INTRODUCTIONT HE C 13 (a,w)0 16 reaction has been extensively investigated 1-5 at a-particle bombarding energies below 5 MeV. Resonances from sharp energy states of the compound nucleus O 17 are observed. We have measured 6 the C 13 (a,a)C 13 differential elastic-scattering cross sections for a-particle bombarding energies from 2.0 to 3.5 MeV at center-of-mass angles 54.7, 107.9,142.6, and 169.6°. C ls (a,n)O u differential reaction cross sections at 0° were measured simultaneously. Elastic-scattering and reaction data were analyzed to determine the J T and the a-particle and neutron partial widths of the states of O 17 corresponding to the observed resonances.The range 2 to 3.5 MeV of a-particle bombarding energies corresponds to the range 7.9 to 9 MeV of excitation energies in the compound nucleus O 17 . Values of / and of neutron and a-particle partial widths for many of the states at these excitation energies were known from C 13 (a,w)0 16 differential cross sections 2-5 and from total cross sections of O 16 for neutrons. 2 -5 » 7 From interference terms in C 13 (a,w)0 16 angular distributions, 4 -5 relative parities of a number of states were known. To determine parities and to make complete determinations of J and partial-width values, C 13 -(a,a)C 13 and O u (n y n)O u elastic-scattering experiments are necessary. The parameters of two states at the low end of the energy interval have recently been determined from analysis of 0 16 (^,w)0 16 angular distributions. 8

Study of the excitation function for the 13C + 4He elastic scattering with the thick-target inverse kinematics method

“…There were several attempts to measure the exci tation function of the 13 C(α, α) 13 C reaction at low energies [11][12][13]. These works were mainly stimu lated by interest in the properties of resonance states in 17 O in astrophysical studies.…”

“…These works were mainly stimu lated by interest in the properties of resonance states in 17 O in astrophysical studies. The first two studies [11,12] gave important information on dominant groups in the spectrum, but the corresponding experiments were performed with targets with com paratively low enrichment in the 13 C isotope (~50%) and analysis was performed within the simplified (single level) R matrix approach, which could not ensure the accuracy necessary for astrophysics. The extensive work with more complete experimental data was recently performed at the University of Notre Dame (United States) [13].…”

Testing Compound Nucleus Hypothesis Across the 17O Nucleus Excitation

“…The study of reactions that refer to the excited compound nucleus 17 O* is of strong concern for reactors physics nuclear data evaluators. 16 O is the most predominant isotope of oxygen in nature and contributes to 4 He gaz production observed in reactor through 16 O(n,α) 13 C conversion. On this point of view, the 16 O constitutes an important safety issue in the operation of reactors.…”

“…Existing nuclear data discrepancies between measured and evaluated data according to the 16 O(n,α) 13 C and reciprocal 13 C(α,n) 16 O reactions, have been the subject of strong * Corresponding author, e-mail : aloys.nizigama@cea.fr ,…”

Development of a non-destructive micro-analytical method for stable carbon isotope analysis of transmission electron microscope (TEM) samples

“…When alpha particles accelerated to 2.751 MeV encounter a carbon-bearing sample, 13 C displays a resonant behavior that significantly increases its effective cross section relative to its Rutherford cross section (Fig. 1), whereas the cross section of 12 C simultaneously decreases [4][5][6]. Thus, if the resonance effect is utilized, and at least 250.000 counts of 13 C nuclei-ion interactions (assuming a normal Poisson distribution) are obtained, it is possible to separate distinct 12 C and 13 C peaks and achieve a ±2 per mil accuracy in the 13 C analysis.…”