Test for isotopic dependence of electron screening in fusion reactions

Engstler, S.; Raimann, G.; Angulo, C.; Greife, U.; Rolfs, C.; Schröder, U.; Somorjai, E.; Kirch, B.; Langanke, K.

doi:10.1016/0370-2693(92)91833-u

Cited by 85 publications

(82 citation statements)

References 16 publications

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“…[81][82][83][84][85], and is determined over most of the energy interval of interest to us by the data of Rolfs et al [83]. We have kept the data of Engstler et al [84] below 50 keV in our fit, even though the slight rise in this data set FIG. 11.…”

Section: Li(p α) 4 Hementioning

confidence: 99%

Estimating reaction rates and uncertainties for primordial nucleosynthesis

2000

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We present a Monte Carlo method for direct incorporation of nuclear inputs in primordial nucleosynthesis calculations. This method is intended to remedy shortcomings of current error estimation, by eliminating intermediate data evaluations and working directly with experimental data, allowing error estimation based solely on published experimental uncertainties. This technique also allows simple incorporation of new data and reduction of errors with the introduction of more precise data. Application of our method indicates that previous error estimates on the calculated abundances were too large by as much as a factor of three. Since uncertainties in the BBN calculation currently dominate inferences drawn from light-element abundances, the re-estimated errors have important consequences for cosmic baryon density, neutrino physics, and lithium depletion in halo stars. Our direct method allows detailed discussion of the status of the nuclear inputs, by identifying clearly the places where improved cross section measurements would be most useful. 26.35.+c, 98.80.Ft

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Section: Li(p α) 4 Hementioning

confidence: 99%

Estimating reaction rates and uncertainties for primordial nucleosynthesis

2000

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“…Experimental data for the reaction are shown, along with our fit (solid line), "1σ" and "2σ" uncertainties in our fit (symmetrical dot-dash lines), and the standard fit of Harris et al [12] (long dash line). Data are those of > Gemeinhardt [13], Fiedler & Kunze [15], < Spinka et al [16], ✷ Kwon et al [14], ✸ Shinozuka et al [17], ⋆ Elwyn et al [18], △ Marion et al [19], × Várnagy et al [20], and ▽ Engstler et al [10].…”

Section: Figmentioning

confidence: 99%

“…The low-energy (100 keV < E <1000 keV) cross-section for this reaction is sufficiently well-known that recent work [10] has concentrated on determining the effects of electron screening in the experimental target at extremely low energies (E < 100 keV) via comparison with the higher-energy cross section. The energy range that concerns us here is the range in which the peaks of the Coulomb barrier penetration factor and of the Maxwell-Boltzmann thermal velocity distribution overlap significantly at BBN temperatures.…”

Section: Hementioning

confidence: 99%

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Nuclear reaction rates and primordial6Li

1997

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We examine the possibility that Big Bang Nucleosynthesis (BBN) may produce non-trivial amounts of 6 Li. If a primordial component of this isotope could be observed, it would provide a new fundamental test of Big-Bang cosmology, as well as new constraints on the baryon density of the universe. At present, however, theoretical predictions of the primordial 6 Li abundance are extremely uncertain due to difficulties in both theoretical estimates and experimental determinations of the 2 H(α, γ) 6 Li radiative capture reaction cross-section. We also argue that present observational capabilities do not yet allow the detection of primeval 6 Li in very metal-poor stars of the galactic halo. However, if the critical cross section is towards the upper end of its plausible range, then improvements in 6 Li detection capabilities may allow the establishment of 6 Li as another product of BBN. It is also noted that a primordial 6 Li detection could help resolve current concerns about the extragalactic D/H determination. 26.35.+c,26.44.+h,25.90.+k

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“…Recently, in several reactions with light nuclei, such as the 3 He + d, 6,7 Li + d and 6,7 Li + p reactions, the deduced astrophysical S-factors for very low energies were found to be larger than those extrapolated from higher energy data. 1,2) The deviation seems to occur below the incident energy of about 20 keV for the 3 He + d reaction and about 80 keV for the Li+p,d reactions; corresponding classical closest distances at theses energies are 140 and 70 fm, respectively. Therefore, nuclei which sit each other in the distance farther than about 100 fm might experience a weaker repulsive potential than the Coulomb potential between the two bare nuclei.…”

Section: §1 Introductionmentioning

confidence: 92%

Measurements of the D+D Reaction in Ti Metal with Incident Energies between 4.7 and 18 keV

Kasagi

Murakami²,

Yajima

et al. 1995

J. Phys. Soc. Jpn.

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The D+D reactions in Ti metal were investigated for the deuteron incident energies between 4.7 and 18 keV. Observed were protons, tritons and 3 He particles emitted in the deuteron bombardment on TiD x . Thick target yields for the D(d, p) T and D(d, n) 3 He reactions were measured at bombarding energies down to 4.7 and 5.4 keV, respectively, for the first time. They were well explained with the reported astrophysical S-factors which were deduced from gas target measurements at E d > 6 keV for the D(d, p)T reaction and E d > 13.3 keV for the D(d, n) 3 He reaction. The cross section ratio σ(d, p)/σ(d, n) was obtained down to 6.4 keV, and was found to be constant at around 1.0 for E d <20 keV. KEYWORDS: D+D reaction in Ti, D(d, p)T and D(d, n)3 He reactions, thick target yields, astrophysical S-factor, cross section ratios §1. Introduction At energies far below the Coulomb barrier, cross sections of nuclear reactions are essentially dominated by the Coulomb penetration factor. An astrophysical S-factor, which contains information on pure nuclear part, is deduced by dividing the reaction cross section by the Coulomb penetration factor of two nuclei. Recently, in several reactions with light nuclei, such as the 3 He + d, 6,7 Li + d and 6,7 Li + p reactions, the deduced astrophysical S-factors for very low energies were found to be larger than those extrapolated from higher energy data.1,2) The deviation seems to occur below the incident energy of about 20 keV for the 3 He + d reaction and about 80 keV for the Li+p,d reactions; corresponding classical closest distances at theses energies are 140 and 70 fm, respectively. Therefore, nuclei which sit each other in the distance farther than about 100 fm might experience a weaker repulsive potential than the Coulomb potential between the two bare nuclei. This behavior is associated with an effect of the screening caused by surrounding electrons, since the target nuclei are in the form of neutral atoms or molecules in the laboratory. However, the observed enhancement of the S-factors is not fully understood as the electron screening effect.3) Thus, measurements of reaction cross sections at very low energies under various circumstances are highly interested.

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Test for isotopic dependence of electron screening in fusion reactions

Cited by 85 publications

References 16 publications

Estimating reaction rates and uncertainties for primordial nucleosynthesis

Estimating reaction rates and uncertainties for primordial nucleosynthesis

Nuclear reaction rates and primordial6Li

Measurements of the D+D Reaction in Ti Metal with Incident Energies between 4.7 and 18 keV

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