He3(α, γ)Be7Reaction

Abstract

The He 3 (a,y)Be 7 reaction has been investigated using gaseous helium targets behind thin nickel foils and using monoenergetic alpha-particle beams with energies from 0.42 to 5.80 MeV. The prompt gamma rays were detected using Nal(Tl) scintillation spectrometers, and the resulting pulse-height spectra were analyzed to determine both the total capture cross section and the branching ratio between the cascade and the crossover transitions as functions of energy. These cross-section measurements have been used to obtain a new value for the zero-energy intercept of the cross-section factor S{E) for this reaction: ^0 = 0.47^0.05 keV-b, and (dS/dE) 0 = -2.8X10" 4 b.

Constraining the Astrophysical S Factor of the 3He(α,γ)7Be Reaction

“…∼700-2800 keV by using the activation method. Three data points obtained with low statistical error contribution [15] particularly show a good agreement with the ERNA data [11] and disagree with those from Parker et al [10]. A good agreement of our results and those from the ERNA collaboration is also seen when comparing with the recent measurements obtained by the ATOMKI collaboration using the activation technique [16].…”

“…The brown filled circle shows the value obtained using the activation technique at TRIUMF. The S factors from Parker et al [10] and LUNA [22,23], ERNA [11], ATOMKI [16], Weizmann [21], Notre Dame [24] and Seattle [25] collaborations are also shown for comparison.…”

“…Large discrepancies are observed in the region 1000-3000 keV, where only data from Parker et al [10] and the ERNA collaboration [11] were available before the measurements performed by our collaboration. Also, discrepancies are seen in the same energy region when comparing different calculations, e.g.…”

Estimating reaction rates and uncertainties for primordial nucleosynthesis

“…The apparent discrepancy at 2σ between experiments that observe capture gamma rays from this process (Refs. [64][65][66][67][68][69]) and those that observe photons from the 7 Be decay (Refs. [69][70][71]) is well-known from discussions of the solar neutrino problem [72].…”

Comparison of the LUNA3He(α, γ)7Be activation results with earlier measurements and model calculations

“…Until the 1980's the 3 He(α, γ) 7 Be cross section has been measured seven times [10,11,12,13,14,15,16] with the on-line method and three times with activation [14,17,18]. The experiments have been carried out in a wide range of energies and using very different experimental techniques.…”