Measurement of²⁵Mg(p, γ)²⁶Al resonance strengths via gamma spectrometry

Abstract

Abstract. The COMPTEL instrument performed the first mapping of the 1.809 MeV photons in the Galaxy, triggering considerable interest in determing the sources of interstellar 26 Al. The predicted 26 Al is too low compared to the observation, for a better understanding more accurate rates for the 25 Mg(p, γ) 26 Al reaction are required. The 25 Mg(p, γ) 26 Al reaction has been investigated at the resonances at Er ‡= 745, 418, 374, 304 keV at Ruhr-Universität-Bochum using a Tandem accelerator and a 4π NaI detector. In addition the resonance at Er = 189 keV has been measured deep underground laboratory at Laboratori Nazionali del Gran Sasso, exploiting the strong suppression of cosmic background. This low resonance has been studied with the 400 kV LUNA accelerator and a HPGe detector. The preliminary results of the resonance strengths will be reported. The

Direct measurement of the15N(p,γ)16O total cross section at novae energies

“…The experiment has been performed at LUNA in Italy's Gran Sasso underground laboratory (LNGS). The LUNA facility has been designed for measuring low nuclear cross sections for astrophysical purposes [13][14][15][16][17][18][19], benefiting from its ultra-low laboratory γ -ray background [20,21].…”

“…• the 4.4 MeV γ -ray from the decay of the first excited state of 12 C populated both in the 11 B(p,γ ) 12 C and in the 15 N(p,αγ ) 12 C reactions (well visible in all the nitrogen spectra, visible in some of the helium spectra), • the ∼5.5 MeV peak from the 2 H(p,γ ) 3 He reaction (visible only for E p 150 keV in both the nitrogen and helium spectra), • the 6.1 MeV γ -ray from the decay of the second excited state of 16 O populated in the 19 F(p,αγ ) 16 O reaction (visible only for E p 180 keV in the helium spectra), • the 6.2 MeV and 6.8 MeV secondary γ -rays and the ∼7.5 MeV summing peak from the 14 N(p,γ ) 15 O reaction (well visible in all the nitrogen spectra, not visible in the helium spectra), • the ∼7.7 MeV peak from the 13 C(p,γ ) 14 N reaction (well visible in the helium spectra, covered by the 14 N(p,γ ) 15 O lines in the nitrogen spectra) and • the 8.1 MeV summing peak from the 18 O(p,γ ) 19 F reaction (visible only in a few helium spectra).…”

Charged-particle thermonuclear reaction rates: II. Tables and graphs of reaction rates and probability density functions

“…[131] where an upper limit on the proton partial width was derived for a p-wave resonance). We disregarded the (ground state) resonance strengths measured by Arazi et al [9] using accelerator mass spectrometry since their strength of the 189 keV resonance in particular seems far too small (see also Formicola et al [92]). The direct capture S-factor is adopted from Endt and Rolfs [82].…”

Ultra-sensitive in-beam $ \gamma$ -ray spectroscopy for nuclear astrophysics at LUNA

“…The γ-rays with E γ > 3 MeV discussed in the previous study [12] are characteristic of radiative capture reactions with Q-values also above 3 MeV. In recent years, several such reactions have been studied at LUNA or are presently under study: -the 2 H(p,γ) 3 He reaction [13], Q-value 5.493 MeV, important for hydrogen burning by the proton-proton chain in the Sun [14], -the 14 N(p,γ) 15 O reaction [15,16,17,18,19], Q-value 7.297 MeV, bottleneck of the CNO cycle, important for solar neutrinos [20], globular cluster ages [21], and hydrogen shell burning in asymptotic giant branch stars [22,23], -the 25 Mg(p,γ) 26 Al reaction [24], Q-value 6.306 MeV, controlling the nucleosynthesis of radioactive 26 Al, a tracer of live nucleosynthesis [25], and the 15 N(p,γ) 16 O reaction, Q-value 12.127 MeV, important in nova nucleosynthesis [26]. Recently, the technique of underground in-beam γ-spectrometry has been extended to radiative capture reactions with Q-values below 3 MeV: -The 3 He(α,γ) 7 Be reaction has been studied at LUNA, both by activation [27,28,29] and by in-beam γ-spectro-metry [29,30].…”