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Newton, Joseph; Iliadis, Christian; Champagne, Arthur E; Cesaratto, J. M.; Daigle, S.; Longland, R.

doi:10.1103/physrevc.81.045801

Cited by 33 publications

(60 citation statements)

References 25 publications

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“…In-beam γ -spectroscopy measurement of Newton et al [10] provided a total cross section at 500 keV proton energy which again coincides with our data point, taking into account the energy uncertainties. The value is taken from Table I of [10]. Kontos et al [11] do not provide total cross section data directly at (E) p = 500 keV.…”

Section: Discussionsupporting

confidence: 91%

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Cross section measurement of the astrophysically important O17(p,γ)F18
Gyürky
¹
,
Ornelas
²
,
Fülöp
³

et al. 2017
Phys. Rev. C
12
0
6
0
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Background:The 17 O(p,γ ) 18 F reaction plays an important role in hydrogen burning processes in several different stages of stellar evolution. The rate of this reaction must therefore be known with high accuracy at the relevant temperatures in order to provide the necessary input for astrophysical models. Purpose: The cross section of 17 O(p,γ ) 18 F is characterized by a complicated resonance structure at low energies which needs to be reproduced by theoretical models if a reliable extrapolation to astrophysical energies is required. Experimental data, however, are scarce in a wide energy range, which increases the uncertainty of the extrapolations. The purpose of the present work is therefore to provide consistent and precise cross section values in a wide energy range for the 17 O(p,γ ) 18 F reaction. Method: The cross section is measured using the activation method. This method provides directly the total cross section which can be compared with model calculations. With this technique some typical systematic uncertainties encountered in in-beam γ -spectroscopy experiments can be avoided. Results: The cross section was measured between 500 keV and 1.8 MeV proton energies with a total uncertainty of typically 10%. The results are compared with earlier measurements and it is found that the gross features of the 17 O(p,γ ) 18 F excitation function are relatively well reproduced by the present data. Deviation of roughly a factor of 1.5 is found in the case of the total cross section when compared with the only high energy dataset. At the lowest measured energy our result is in agreement with two recent datasets within one standard deviation and deviates by roughly two standard deviations from a third one. An R-matrix analysis of the present and previous data strengthens the reliability of the extrapolated zero energy astrophysical S factor. Conclusions: Using an independent experimental technique, the literature cross section data of 17 O(p,γ ) 18 F is confirmed in the energy region of the resonances while a lower direct capture cross section is recommended at higher energies. The present dataset provides a constraint for the theoretical cross sections.

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Section: Discussionsupporting

confidence: 91%

“…After the turn of the century, several experimental studies were carried out, mostly concentrating on the low energy region below about 500 keV [4,[6][7][8][9][10][11][12][13][14]. (The only exception was the work of Kontos et al [11] which extended up to 1.6 MeV.)…”

Section: Introductionmentioning

confidence: 99%

Cross section measurement of the astrophysically important O17(p,γ)F18
Gyürky
¹
,
Ornelas
²
,
Fülöp
³

et al. 2017
Phys. Rev. C
12
0
6
0
View full text Add to dashboard Cite

show abstract

“…17 O(p,α) 14 N. Several experiments (Chafa et al 2007;Newton et al 2010;Moazen et al 2007) have determined the magnitude of most of the several resonances that influence the rate of this reaction. As for the 17 O(p,γ) 18 F, the E cm = 65 keV resonance, directly at the astrophysically relevant energy, makes the reaction rate determination difficult, and the uncertainty is correspondingly large.…”

Section: Reaction Rate Uncertaintiesmentioning

confidence: 99%

“…After the pioneering work of Rolfs (1973) in the seventies, several studies (Fox et al 2005;Chafa et al 2007;Newton et al 2010;Hager et al 2012;Kontos et al 2012;Scott et al 2012) have determined the reaction rate with improving precision in the past decade. Nevertheless, at the temperatures relevant for AGB nucleosynthesis, the reaction rate is dominated by the lowest energy resonance, E cm = 65 keV, which is too weak to be directly measured with the current experiment possibilities.…”

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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“…The ratio between the reaction rates of 17 O(p,α) 14 N (Q = 1.2 MeV) and 17 O(p,γ) 18 F (Q = 5.6 MeV) channels is one of the most important parameters for the galactic synthesis of 17 O, the stellar production of radioactive 18 F, and for predicted O isotopic ratios in premolar grains [37,38].…”

Section: The Other Cno Cyclesmentioning

confidence: 99%

Nuclear Astrophysics in underground laboratories: the LUNA experiment

Simpson¹,

Simenel²,

Cook³

et al. 2017

EPJ Web Conf.

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Abstract. One of the main ingredients of nuclear astrophysics is the knowledge of the thermonuclear reactions responsible for powering the stellar engine and for the synthesis of the chemical elements. At astrophysical energies the cross section of nuclear processes is extremely reduced by the effect of the Coulomb barrier. The low value of cross sections prevents their measurement at stellar energies on Earth surface and often extrapolations are needed. The Laboratory for Underground Nuclear Astrophysics (LUNA) is placed under the Gran Sasso mountain and thanks to the cosmic-ray background reduction provided by its position can investigate cross sections at energies close to the Gamow peak in stellar scenarios. Many crucial reactions involved in hydrogen burning has been measured directly at astrophysical energies with both the LUNA-50kV and the LUNA-400kV accelerators, and this intense work will continue with the installation of a MV machine able to explore helium and carbon burnings. Based on this progress, currently there are efforts in several countries to construct new underground accelerators. In this talk, the typical techniques adopted in underground nuclear astrophysics will be described and the most relevant results achieved by LUNA will be reviewed. The exciting science that can be probed with the new facilities will be highlighted.

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Measurement ofO17(p,γ)

Cited by 33 publications

References 25 publications

Cross section measurement of the astrophysically important O17(p,γ)F18
Gyürky
¹
,
Ornelas
²
,
Fülöp
³

et al. 2017
Phys. Rev. C
12
0
6
0
View full text Add to dashboard Cite

Cross section measurement of the astrophysically important O17(p,γ)F18
Gyürky
¹
,
Ornelas
²
,
Fülöp
³

et al. 2017
Phys. Rev. C
12
0
6
0
View full text Add to dashboard Cite

Effects of nuclear cross sections on¹⁹F nucleosynthesis at low metallicities

Nuclear Astrophysics in underground laboratories: the LUNA experiment

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Measurement ofO17(p,γ)

Cited by 33 publications

References 25 publications

Cross section measurement of the astrophysically important O17(p,γ)F18Gyürky1, Ornelas2, Fülöp3 et al. 2017Phys. Rev. C12060View full textAdd to dashboardCite

Cross section measurement of the astrophysically important O17(p,γ)F18Gyürky1, Ornelas2, Fülöp3 et al. 2017Phys. Rev. C12060View full textAdd to dashboardCite

Effects of nuclear cross sections on19F nucleosynthesis at low metallicities

Nuclear Astrophysics in underground laboratories: the LUNA experiment

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Cross section measurement of the astrophysically important O17(p,γ)F18
Gyürky
¹
,
Ornelas
²
,
Fülöp
³

et al. 2017
Phys. Rev. C
12
0
6
0
View full text Add to dashboard Cite

Cross section measurement of the astrophysically important O17(p,γ)F18
Gyürky
¹
,
Ornelas
²
,
Fülöp
³

et al. 2017
Phys. Rev. C
12
0
6
0
View full text Add to dashboard Cite

Effects of nuclear cross sections on¹⁹F nucleosynthesis at low metallicities