Niveaux excités du F19 par l'étude de la réaction O18(p, α0)N15 entre 2.2 et 6 MeV

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

doi:10.1016/0029-5582(63)90749-1

Cited by 9 publications

(36 citation statements)

References 6 publications

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“…2). In addition, they were observed [3,12] in the reaction 180(p, :q+zV)lSN, and the lower resonance in the ~SO(p, 7.0)15N reaction. From the decay into these channels one has to conclude that the wave functions of the two states contain considerable T= 1/2 admixtures.…”

Section: Discussionmentioning

confidence: 82%

Investigation of two resonances in the18O(p, n)18F reaction

Fritsch¹,

Büchs²,

Finckh³

et al. 1973

Z. Physik

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Excitation functions for the 180(p, n)lSF reaction were measured at bombarding energies Ep=4.6 to 6.6 MeV. In and near two resonances of the yield curves at Ep-----5.622 and 6.061 MeV, angular distributions were measured with neutron timeof-flight techniques. The strong neutron decay to the T= 1 state in 18F and the similarity of the 1SO(p, n) and 180(n, n) yield curves give good evidence that the structures in the 180(p, n) yield curve arise from the formation of T= 3/2 states in 19F. A twolevel-analysis does not give satisfactory fits to the strongly asymmetric angular distributions.

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Section: Discussionmentioning

confidence: 82%

Investigation of two resonances in the18O(p, n)18F reaction

Fritsch¹,

Büchs²,

Finckh³

et al. 1973

Z. Physik

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“…Recent analysis [1] of low-density graphite grains from the Orgueil meteorite show spatially-correlated excesses of 15 N and 18 O, suggesting a contribution of material originating from the inner part of the helium-rich zone of an exploding massive star [2]. In this helium-rich layer, helium was being burnt into carbon and oxygen when the supernova occurred, causing a shockwave to pass through the outer layers of the star.…”

mentioning

confidence: 99%

“…Under normal pre-supernova conditions, during which the mass fraction of neutrons is very low, this 18 F undergoes β + decays into 18 O. During the supernova explosion the 18 O(α, n) 21 Ne reaction begins to operate, supplying neutrons which can react with 18 F, resulting in 18 F(n, α) 15 N and 18 F(n, p) 18 O reactions. The temperatures in the helium-rich zone reach peak post-shock temperatures of 0.4 − 0.7 GK, corresponding to a range of thermal energies of kT = 35 − 60 keV.…”

mentioning

confidence: 99%

“…The recommendation of the sensitivity study of Bojazi and Meyer [2] is that the focus of future evaluations of the 18 F+n reaction rates should attempt to de-scribe the competition between the proton and α-particle exit channels. This is particularly important because of the interplay between the two reactions: greater proton production from 18 F(n, p) 18 O produces 15 N via the 18 F(n, p) 18 O(p, α) 15 N reaction chain whilst also destroying it via proton absorption in the 15 N(p, α) 12 C reaction. An increased production of 15 N through the 18 F(n, α) 15 N reaction also results in a decreased destruction of 15 N through the 15 N(p, α) 12 C reaction enabled by the protons produced in the competing 18 F(n, p) 18 O reaction.…”

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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“…The increasingly demanding requirements imposed on calorimeters in both xed target and collider mode for existing and future heavy{ion and hadron accelerators has lead to the relatively recent development of the quartz ber calorimetry (QCal) technique [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. The primary characteristics of interest for such calorimeters are the impressive potential for the radiation hardness of amorphous silica [3,15,21] (SiO 2 , often referred to simply as \quartz"), the intrinsic speed of a device which relies on Cherenkov{eect light for information and the small eective shower radius [15,6,19].…”

Section: Introductionmentioning

confidence: 99%

On the electromagnetic energy resolution of Cherenkov-fiber calorimeters

Lundin

Contin

Dellacasa

et al. 1996

Nuclear Instruments and Methods in Physics Research Section A:

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Electromagnetic calorimeters which sample the Cherenkov radiation of shower particles in optical bers operate in a markedly dierent manner from calorimeters which rely on the dE/dx of shower particles. The well-understood physics of electromagnetic shower development is applied to the case of Cherenkov-ber calorimetry (also known as quartz ber calorimetry) and the results of systematically performed studies are considered in detail to derive an understanding of the critical parameters involved in energy measurement using such calorimeters. A quantitative parameterization of Cherenkov-ber calorimetry electromagnetic energy resolution is proposed and compared with existing experimental results.

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Niveaux excités du F19 par l'étude de la réaction O18(p, α0)N15 entre 2.2 et 6 MeV

Cited by 9 publications

References 6 publications

Investigation of two resonances in the18O(p, n)18F reaction

Investigation of two resonances in the18O(p, n)18F reaction

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

On the electromagnetic energy resolution of Cherenkov-fiber calorimeters

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