New measurement of the astrophysically important<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msup><mml:mrow /><mml:mn>40</mml:mn></mml:msup></mml:math>Ca(<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msup><mml:mrow><mml:mrow><mml:mi mathvariant="bold-italic">α</mml:mi></mml:mrow><mml:mo>,</mml:mo><mml:mi>γ</mml:mi><mml:mo>)</mml:mo></mml:mrow><mml:mn>44</mml:mn></mml:msup></mml:math>Ti reaction

Robertson, Daniel; Collon, P.; Wiescher, M.; Becker, Hans‐Werner

doi:10.1103/physrevc.85.045810

Cited by 24 publications

(37 citation statements)

References 38 publications

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“…Moreover, even if the CC method should be involved for a rigorous treatment of reactions on deformed nuclei, it is considered not suited for large-scale calculations for astrophysics [20] and fusion technology as well. Thus, an effective spherical optical potential is yet concerned in this respect, to obtain SM reliable predictions for nuclei heavier than A∼40 and close to the valley of stability [81]. Nevertheless, beyond the present revision of a global OMP, both the involved α-particle OMP and the crosssection predictions will benefit from further CC analysis of specific α-particle induced reactions.…”

Section: Discussionmentioning

confidence: 99%

Further explorations of theα-particle optical model potential at low energies for the mass rangeA≈45–209

2014

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The recent high-precision measurements of α-particle induced reaction data below the Coulomb barrier (B) make possible the understanding of limits and possible improvement of a previous optical model potential (OMP) for α-particles on nuclei within the mass number range 45≤A≤209 [M. Avrigeanu et al., Phys. Rev. C 82, 014606 (2010)]. An updated version of this potential is given in the present work concerning mainly an increased surface imaginary potential depth well below B for A>130. Moreover, underestimation of reaction cross sections for well-deformed nuclei is removed by using ∼7% larger radius for the surface imaginary part of this spherical OMP. Improved input parameters based on recent independent data, particularly γ-ray strength functions, but no empirical rescaling factor of the γ and/or neutron widths have been involved within statistical model calculation of the corresponding (α, x) reaction cross sections.

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Section: Discussionmentioning

confidence: 99%

Further explorations of theα-particle optical model potential at low energies for the mass rangeA≈45–209

2014

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“…Again similar to 42 Ca, at very low energies close above the (α,p) threshold, the (α,p) reaction is further suppressed by the Coulomb barrier in the exit channel, and consequently the total reaction cross section is significantly affected by the (α,γ) cross section. However, average cross sections for the 40 Ca(α,γ) 44 Ti reaction are very rare in literature, and the focus of recent (α,γ) experiments was the astrophysically very important resonance triplet around 4.5 MeV and the properties of resonances [79,80,81,82,83,84,85]. The thick-target data point of Nassar et al [81] leads to an average cross section of 8.0 ± 1.1 µb for the broad energy range from about 2.1 to 4.2 MeV in the center-of-mass system.…”

Section: Camentioning

confidence: 99%

Cross sections of α-induced reactions for targets with masses A ≈ 20–50 at low energies

Mohr

2015

Eur. Phys. J. A

100

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Abstract. A simple reduction scheme using so-called reduced energies E red and reduced cross sections σ red allows the comparison of heavy-ion induced reaction cross sections for a broad range of masses of projectile and target and over a wide energy range. A global behavior has been found for strongly bound projectiles whereas much larger reduced cross sections have been observed for weakly bound and halo projectiles. It has been shown that this simple reduction scheme works also well for α-particle induced reactions on heavy target nuclei, but very recently significant deviations have been seen for α+ 33 S and α+ 23 Na. Motivated by these unexpected discrepancies, the present study analyses α-induced reaction cross sections for targets with masses A ≈ 20 − 50. The study shows that the experimental data for α-induced reactions on nuclei with A ≈ 20 − 50 deviate slightly from the global behavior of reduced cross sections. However, in general the deviations evolve smoothly towards lower masses. The only significant outliers are the recent data for 33 S and 23 Na which are far above the general systematics, and some very old data may indicate that 36 Ar and 40 Ar are below the general trend. As expected, also the doubly-magic 40 Ca nucleus lies slightly below the results for its neighboring nuclei. Overall, the experimental data are nicely reproduced by a statistical model calculation utilizing the simple α-nucleus potential by McFadden and Satchler. Simultaneously with the deviation of reduced cross sections σ red from the general behavior, the outliers 23 Na, 33 S, 36 Ar, and 40 Ar also show significant disagreement between experiment and statistical model calculation.PACS. 25.55.-e 3H-, 3He-, and 4He-induced reactions -24.10.Pa Thermal and statistical models

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“…For example, the thick (thin) black lines indicate the high and low Monte Carlo rates for a coverage probability of 68% (95%). The blue and green lines show the rates obtained using conventional (i.e., pre-Monte Carlo) methods: (blue) previous rates, 55 where the unobserved lowenergy resonances were disregarded; (green) upper limit obtained if the maximum contribution of the unobserved resonance at E c.m. α = 2373 keV is adopted.…”

Section: B Upper Limits Of Nuclear Physics Input Parametersmentioning

confidence: 99%

Nuclear astrophysics in the laboratory and in the universe

2014

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Nuclear processes drive stellar evolution and so nuclear physics, stellar models and observations together allow us to describe the inner workings of stars and their life stories. This Information on nuclear reaction rates and nuclear properties are critical ingredients in addressing most questions in astrophysics and often the nuclear database is incomplete or lacking the needed precision. Direct measurements of astrophysically-interesting reactions are necessary and the experimental focus is on improving both sensitivity and precision. In the following, we review recent results and approaches taken at the Laboratory for Experimental Nuclear Astrophysics (LENA, http://research.physics.unc.edu/project/nuclearastro/Welcome.html).

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New measurement of the astrophysically important40Ca(α,γ)44Ti reaction

Cited by 24 publications

References 38 publications

Further explorations of theα-particle optical model potential at low energies for the mass rangeA≈45–209

Further explorations of theα-particle optical model potential at low energies for the mass rangeA≈45–209

Cross sections of α-induced reactions for targets with masses A ≈ 20–50 at low energies

Nuclear astrophysics in the laboratory and in the universe

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