Resonance strengths in the N14 ( p,γ)O15

Abstract

Background: The 14 N(p, γ) 15 O reaction plays a vital role in various astrophysical scenarios. Its reaction rate must be accurately known in the present era of high precision astrophysics. The cross section of the reaction is often measured relative to a low energy resonance, the strength of which must therefore be determined precisely. Purpose: The activation method, based on the measurement of 15 O decay, has not been used in modern measurements of the 14 N(p, γ) 15 O reaction. The aim of the present work is to provide strength data for two resonances in the 14 N(p, γ) 15 O reaction using the activation method. The obtained values are largely independent from previous data measured by in-beam γ spectroscopy and are free from some of their systematic uncertainties. Method: Solid state TiN targets were irradiated with a proton beam provided by the Tandetron accelerator of Atomki using a cyclic activation. The decay of the produced 15 O isotopes was measured by detecting the 511 keV positron annihilation γ rays. Results: The strength of the E p = 278 keV resonance was measured to be ωγ 278 = (13.4 ± 0.8) meV while for the E p = 1058 keV resonance ωγ 1058 = (442 ± 27) meV. Conclusions: The obtained E p = 278 keV resonance strength is in fair agreement with the values recommended by two recent works. However, the E p = 1058 keV resonance strength is about 20% higher than the previous value. The discrepancy may be caused in part by a previously neglected finite target thickness correction. As only the low energy resonance is used as a normalization point for cross section measurements, the calculated astrophysical reaction rate of the 14 N(p, γ) 15 O reaction and therefore the astrophysical consequences are not changed by the present results.

Stable beam experiments in wide energy ranges serving low energy nuclear astrophysics

“…The strengths of two strong narrow resonances in 14 N(p,γ) 15 O have already been measured and the results published [11]. The lower one at E p = 278 keV is especially important as it serves as a normalization point in several experiments.…”

“…For example, the most uncertain input parameter for alpha-induced reactions is the alpha-nucleus 15 O from the literature and from the present work. For the references see the bibliography in [11]. optical potential.…”

“…Strengths of the two measured resonances in 14 N(p,γ)15 O from the literature and from the present work. For the references see the bibliography in[11].…”

Setup commissioning for an improved measurement of the D(p,$$\gamma $$)$$^3$$He cross section at Big Bang Nucleosynthesis energies

“…The 14 N(p,γ 1 γ 2 ) 15 O reaction has been studied extensively by the LUNA collaboration [30; 31]. At the resonant energy E r = 259 keV [32] (in the centre of mass system; Γ = 0.99 keV [22]) this reaction mainly proceeds through three exit channels with known branching ratios (BR), each producing two prompt γ rays in cascade: 1) 765 + 6792 keV (BR=23.0%), 2) 1384 + 6172 keV (BR=58.3%) and 3) 2375 + 5181 keV (BR=16.9%) [33]. In order to measure the photo-peak efficiency (z, E γ ) of Ge1 as a function of γ-ray emission position z along the beam axis (with z = 0 corresponding to the centre of the target chamber) and for all γ-ray energies above, we used the following procedure.…”

Setup commissioning for an improved measurement of the D(p,gamma)3He cross section at Big Bang Nucleosynthesis energies

“…The 14 N(p,γ 1 γ 2 ) 15 O reaction has been studied extensively by the LUNA collaboration Formicola et al, 2004]. At the resonant energy E r = 259 keV [Gyürky et al, 2019] (in the centre of mass system; Γ = 0.99 keV [Daigle et al, 2016]) this reaction mainly proceeds through three exit channels with known branching ratios (BR), each producing two prompt γ rays in cascade: 1) 765 + 6792 keV (BR=23.0%), 2) 1384 + 6172 keV (BR=58.3%) and 3) 2375 + 5181 keV (BR=16.9%) [Marta et al, 2011]. In order to measure the photo-peak efficiency (z, E γ ) of Ge1 as a function of γ-ray emission position z along the beam axis (with z = 0 corresponding to the centre of the target chamber) and for all γ-ray energies above, we used the following procedure.…”