Lifetime measurement of the 6792 keV state in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mmultiscripts><mml:mi mathvariant="normal">O</mml:mi><mml:mprescripts /><mml:none /><mml:mrow><mml:mn>15</mml:mn></mml:mrow></mml:mmultiscripts></mml:math>, important for the astrophysical<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>S</mml:mi></mml:mrow></mml:math>factor extrapolation in<mml:math xmlns:mml="http://www.w3.org/1998/Math/Mat

Schürmann, D.; Kunz, R.; Lingner, I.; Rolfs, C.; Schümann, F.; Strieder, F.; Trautvetter, H. P.

doi:10.1103/physrevc.77.055803

Cited by 31 publications

(26 citation statements)

References 19 publications

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“…The value of the ground state width from the fit is Γ γ (6.79) = 2.7±0.2(stat) eV and is in agreement with the lower limit lifetime measurement by Ref. [34] of >0.85 eV, but is considerably larger than the values of 0.41 +34 −13 eV (90% C.L.) of Ref.…”

supporting

confidence: 74%

Cross section measurement ofN14(p,γ)O15in the CNO cycle

Görres

deBoer

et al. 2016

Phys. Rev. C

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Background The CNO cycle is the main energy source in stars more massive than our sun, it defines the energy production and the cycle time that lead to the lifetime of massive stars, and it is an important tool for the determination of the age of globular clusters. In our sun about 1.6% of the total solar neutrino flux comes from the CNO cycle. The largest uncertainty in the prediction of this CNO flux from the standard solar model comes from the uncertainty in the 14 N(p, γ) 15 O reaction rate, thus the determination of the cross section at astrophysical temperatures is of great interest.Purpose The total cross section of the 14 N(p, γ) 15 O reaction has large contributions from the transitions to the Ex = 6.79 MeV excited state and the ground state of 15 O. The Ex = 6.79 MeV transition is dominated by radiative direct capture, while the ground state is a complex mixture of direct and resonance capture components and the interferences between them. Recent studies have concentrated on cross section measurements at very low energies, but broad resonances at higher energy may also play a role. A single measurement has been made that covers a broad higher energy range but it has large uncertainties stemming from uncorrected summing effects. Further, the extrapolations of the cross section vary significantly depending on the data sets considered. Thus new direct measurements have been made to improve the previous high energy studies and to better constrain the extrapolation.Methods Measurements were performed at the low energy accelerator facilities of the nuclear science laboratory at the University of Notre Dame. The cross section was measured over the proton energy range from Ep = 0.7 to 3.6 MeV for both the ground state and the Ex = 6.79 MeV transitions at θ lab = 0• , 135• and 150• . Both TiN and implanted 14 N targets were utilized. γ-rays were detected using an array of high purity germanium detectors.Results The excitation function as well as angular distributions of the two transitions were measured. A multi-channel Rmatrix analysis was performed with the present data and is compared with previous measurements. The analysis covers a wide energy range so that the contributions from broad resonances and direct capture can be better constrained. ConclusionThe astrophysical S-factors of the Ex = 6.79 MeV and the ground state transitions were extrapolated to low energies with the newly measured differential cross section data. Based on the present work, the extrapolations yield

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supporting

confidence: 74%

Cross section measurement ofN14(p,γ)O15in the CNO cycle

Görres

deBoer

et al. 2016

Phys. Rev. C

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“…In addition to the direct measurement of cross sections, the lifetime of the important 6.792 MeV state was measured using the Doppler-shift attenuation method [46,47] and via Coulomb excitation [48]. The strong external capture components in several transitions led to measurements of the asymptotic normalization coefficients using the 14 N( 3 He,d) 15 O transfer reaction [35,49,50].…”

Section: Experimental Reaction Datamentioning

confidence: 99%

AZURE: AnR-matrix code for nuclear astrophysics

et al. 2010

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The paper describes a multilevel, multichannel R-matrix code, AZURE, for applications in nuclear astrophysics. The code allows simultaneous analysis and extrapolation of low-energy particle scattering, capture, and reaction cross sections of relevance to stellar hydrogen, helium, and carbon burning. The paper presents a summary of R-matrix theory, code description, and a number of applications to demonstrate the applicability and versatility of AZURE.

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“…It is worth noting that a reliable extrapolation of the LUNA data to the solar Gamow peak requires combining low-energy with high-energy data, namely the results of the LENA experiment at TUNL (Runkle et al 2005). Additional information is provided by experiments that used indirect methods, such as the Doppler shift attenuation method (Bertone et al 2001;Schürmann et al 2008), Coulomb excitation (Yamada et al 2004), and asymptotic normalization coefficients (ANC; Mukhamedzhanov et al 2003). It is worth noting that the uncertainty on data at high energy affects the low energy extrapolation.…”

Section: Reaction Rate Uncertaintiesmentioning

confidence: 99%

Effects of nuclear cross sections on¹⁹F nucleosynthesis at low metallicities

Cristallo

Leva

Imbriani

et al. 2014

A&A

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Context. The origin of fluorine is a longstanding problem in nuclear astrophysics. It is widely recognized that asymptotic giant branch (AGB) stars are among the most important contributors to the Galactic fluorine production. Aims. In general, extant nucleosynthesis models overestimate the fluorine production by AGB stars with respect to observations. Although those differences are rather small at solar metallicity, low metallicity AGB stellar models predict fluorine surface abundances up to one order of magnitude larger than the observed ones. Methods. As part of a project devoted to reducing the uncertainties in the nuclear physics that affect the nucleosynthesis in AGB stellar models, we review the relevant nuclear reaction rates involved in the fluorine production or destruction. We perform this analysis on a model with initial mass M = 2 M and Z = 0.001. Results. We found that the major uncertainties are due to the 13 C(α,n) 16 O, the 19 F(α,p) 22 Ne, and the 14 N(p,γ) 15 O reactions. A change in the corresponding reaction rates within the present experimental uncertainties implies surface 19 F variations at the AGB tip lower than 10%, thus much smaller than observational uncertainties. For some α capture reactions, however, cross sections at astrophysically relevant energies are determined on the basis of nuclear models, in which some low-energy resonance parameters are very poorly known. Thus, larger variations in the rates of those processes cannot be excluded. That being so, we explore the effects of the variation in some α capture rates well beyond the current published uncertainties. The largest 19 F variations are obtained by varying the 15 N(α,γ) 19 F and the 19 F(α,p) 22 Ne reactions. Conclusions. The currently estimated uncertainties of the nuclear reaction rates involved in the production and destruction of fluorine produce minor 19 F variations in the ejecta of AGB stars. Analysis of some α capture processes that assume a wider uncertainty range determines 19 F abundances in better agreement with recent spectroscopic fluorine measurements at low metallicity. In the framework of this scenario, the 15 N(α,γ) 19 F and the 19 F(α,p) 22 Ne reactions show the strongest effects on fluorine nucleosynthesis. The presence of poorly known low-energy resonances make such a scenario possible, even if it is unlikely. We plan to measure these resonances directly.

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Lifetime measurement of the 6792 keV state inO15, important for the astrophysicalSfactor extrapolation in
D. Schürmann
¹
,
R. Kunz
²
,
I. Lingner
³

et al.

Cited by 31 publications

References 19 publications

Cross section measurement ofN14(p,γ)O15in the CNO cycle

Cross section measurement ofN14(p,γ)O15in the CNO cycle

AZURE: AnR-matrix code for nuclear astrophysics

Effects of nuclear cross sections on¹⁹F nucleosynthesis at low metallicities

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Lifetime measurement of the 6792 keV state inO15, important for the astrophysicalSfactor extrapolation inD. Schürmann1, R. Kunz2, I. Lingner3 et al.

Cited by 31 publications

References 19 publications

Cross section measurement ofN14(p,γ)O15in the CNO cycle

Cross section measurement ofN14(p,γ)O15in the CNO cycle

AZURE: AnR-matrix code for nuclear astrophysics

Effects of nuclear cross sections on19F nucleosynthesis at low metallicities

Contact Info

Product

Resources

About

Lifetime measurement of the 6792 keV state inO15, important for the astrophysicalSfactor extrapolation in
D. Schürmann
¹
,
R. Kunz
²
,
I. Lingner
³

et al.

Effects of nuclear cross sections on¹⁹F nucleosynthesis at low metallicities