Niveaux excités du 19F par l'étude de la réaction 18O (p, α0) 15N

Gorodetzky, S.; Port, M.P.J. van de; Graff, J.; Thirion, J.

doi:10.1051/jphys:019630024011097801

Cited by 2 publications

(38 citation statements)

References 4 publications

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“…Therefore, if the partial width in the entrance channel to a state using a particular reaction is relatively weak the state may drop below the limit-of-detection. A related effect can be observed comparing the study of Sellin et al [19] with those of Gorodetzky et al [15,16] or Carlson et al [14]: the number of levels observed in the latter two experiments far exceeds the number of those claimed in the former. Careful visual inspection of the spectra of Sellin et al [19] would suggest that some of the states claimed by Gorodetzky and Carlson are, in fact, observed in that experiment but are not treated as such.…”

Section: Ex [Mev]mentioning

confidence: 81%

“…Some direct reactions have been performed populating states in 19 F via a number of different routes, e.g. 18 F(d, p) 19 F [11], 16 O( 6 Li,t) 19 F [12] etc. ; these direct reactions tend to have much poorer energy resolution than the resonance reactions and it is sometimes difficult to firmly identify which states populated in the direct reactions correspond to those observed in resonance reactions.…”

Section: Existing 19 F Nuclear Datamentioning

confidence: 99%

“…The resonance reactions involving 18 O+p have been performed with alumina targets enriched in 18 O [15,16] or thin gas targets [14,19]. Two of the older studies of 18 O+p reactions, those of Carlson et al [14] and Gorodetzky et al [15,16] use the then-current value for the proton threshold of 19 F, a value which is around 30 keV lower than the present, more accurate value [18]. This results in the excitation energies of levels determined in those experiments being around 30 keV below the correct value.…”

Section: Existing 19 F Nuclear Datamentioning

confidence: 99%

“…The excitation-energy values listed in Table I are re-calculated from the available data in Refs. [14][15][16]19] using updated mass measurements [18]. The uncertainties in the excitation energies are also recalculated -in these cases, they are dominated by the uncertainties in the proton bombarding energies.…”

Section: Existing 19 F Nuclear Datamentioning

confidence: 99%

“…[13] [15,16], T = 3/2 10.676 (9) gies may be correlated and that the relative uncertainties in the bombarding energies is smaller.…”

Section: Ex [Mev]mentioning

confidence: 99%

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Charged-particle branching ratios above the neutron threshold in F19 : Constraining N15 production in core-collapse supern

Adsley¹,

Hammache²,

Séréville³

et al. 2021

Phys. Rev. C

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Background: Spatially-correlated overabundances of 15 N and 18 O observed in some low-density graphite meteoritic grains have been connected to nucleosynthesis taking place in the helium-burning shell during core-collapse supernovae. Two of the reactions which have been identified as important to the final abundances of 15 N and 18 O are 18 F(n, α) 15 N and 18 F(n, p) 18 O.Purpose: The relative strengths of the 18 F(n, α) 15 N and 18 F(n, p) 18 O reactions depend sensitively on the relative α0 and p0 decay branches from states above the neutron threshold in 19 F in addition to other properties such as the spins and parities, and the neutron widths. However, experimental data on the charged-particle decays from these highly excited states are lacking or inconsistent.Method: Two experiments were performed using proton inelastic scattering from LiF targets and magnetic spectrographs. The first experiment used the high-resolution Q3D spectrograph at Munich to constrain the properties of levels in 19 F. A second experiment using the Orsay Split-Pole spectrograph and an array of silicon detectors was performed in order to measure the charged-particle decays of neutron-unbound levels in 19 F.Results: A number of levels in 19 F have been identified along with their corresponding charged-particle decays. The first state above the neutron threshold which has an observed proton-decay branch to the ground state of 18 O lies 68 keV (Ex = 10.5 MeV) above the neutron threshold. The α-particle decays from the neutron-unbound levels are generally observed to be much stronger than the proton decays. Conclusion:Neutron-unbound levels in 19 F are observed to decay predominantly by α-particle emission, supporting the role of 18 F(n, α) 15 N in the production of 15 N in the helium-burning shell of supernovae. Improved resonant-scattering reaction data are required in order to be able to determine the reaction rates accurately. I. ASTROPHYSICAL BACKGROUND *

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Section: Ex [Mev]mentioning

confidence: 81%

Section: Existing 19 F Nuclear Datamentioning

confidence: 99%

Section: Existing 19 F Nuclear Datamentioning

confidence: 99%

Section: Existing 19 F Nuclear Datamentioning

confidence: 99%

“…[13] [15,16], T = 3/2 10.676 (9) gies may be correlated and that the relative uncertainties in the bombarding energies is smaller.…”

Section: Ex [Mev]mentioning

confidence: 99%

See 3 more Smart Citations

Charged-particle branching ratios above the neutron threshold in F19 : Constraining N15 production in core-collapse supern

Adsley¹,

Hammache²,

Séréville³

et al. 2021

Phys. Rev. C

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Charged-Particle Decays of Highly Excited States in $$^{19}$$ F

Adsley¹,

Hammache²,

Séréville³

et al. 2019

Springer Proceedings in Physics

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Neutron-capture reactions on 18 F in the helium-burning shell play an important role in the production of 15 N during core-collapse supernovae. The competition between the 18 F(n, p/α) 18 O/ 15 N reactions controls the amount of 15 N produced. The strengths of these reactions depend on the decay branching ratios of states in 19 F above the neutron threshold. We report on an experiment investigating the decay branching ratios of these states in order to better constrain the strengths of the reactions.

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Niveaux excités du 19F par l'étude de la réaction 18O (p, α0) 15N

Cited by 2 publications

References 4 publications

Charged-particle branching ratios above the neutron threshold in F19 : Constraining N15 production in core-collapse supern

Charged-particle branching ratios above the neutron threshold in F19 : Constraining N15 production in core-collapse supern

Charged-Particle Decays of Highly Excited States in $$^{19}$$ F

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