Comparison of 6Li(d, n1) 7Be AND 6Li(d, p1) 7Li mirror reactions at low energies

Cecil, F. E.; Peterson, R.J.; Kunz, P.D.

doi:10.1016/0375-9474(85)90157-5

Cited by 16 publications

(5 citation statements)

References 15 publications

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“…A similar trend was reported for the reaction ratio for the 6 Li + d reactions at very low energies; 14) the experimental ratio cannot be explained either. 3 He reaction to 5.4keV.…”

Section: §2 Experimental Proceduressupporting

confidence: 78%

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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“…A similar trend was reported for the reaction ratio for the 6 Li + d reactions at very low energies; 14) the experimental ratio cannot be explained either. 3 He reaction to 5.4keV.…”

Section: §2 Experimental Proceduressupporting

confidence: 78%

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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“…VBe and 6Li(d, pl)7Li at low energies (E<140keV) it was found [9] that R(E) decreased significantly at low energies. This decrease was interpreted to arise from the Oppenheimer-Phillips effect [10] caused by the polarisation of the incident deuteron in the Coulomb field of the target nucleus (prediction: R(E)<I at E~Ec=respective Coulomb barrier).…”

Section: From a Study Of The Cross Section Ratio R(e)= A(d N)/ A(dmentioning

confidence: 93%

Oppenheimer-Phillips effect and electron screening ind+ d fusion reactions

Greife

Gorris

Junker

et al. 1995

Z. Physik A - Hadrons and Nuclei

168

130

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Abstract. The d(d,n)3He and d(d,p)t fusion reactionshave been studied at center-of-mass energies E = 1.6 to 130 keV using intense beam currents from 30, 100, and 450 kV accelerators in combination with detectors in close and far geometry. The cross sesction ratio, (d,p), approaches unity (within 2%) at low energies; thus there is no experimental evidence for the Oppenheimer-Phillips effect at subcoulomb energies. R(E)=a(d,n)/cr The cross sections of d(d,p)t at E<10 keV show clearevidence for electron screening effects. However, the observed cross section enhancement is significantly larger than can be accounted for from available atomic physics models.

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“…Some decrease at low energies would be expected in a stripping model because the deuteron is polarized in the field of the 6 Li nucleus, so the proton is further from the nuclear center: the Oppenheimer-Phillips effect (OPE) [14]. An attempt to describe this effect phenomenologically [3] led to ambiguous results. Recent experiments [15,16] and more detailed but still simplified theoretical approaches indicate that these effects are too small to explain the (d, n )/(d, p ) data.…”

Section: A General Commentsmentioning

confidence: 99%

“…Measurements of (d, n )/(d, p ) by Cecil, et al [3] and Czerski, et al [4], found significant deviations from unity, but covered a very limited energy range: 0.06-0.18 MeV. An extensive set of measurements, comparing the 7 Li (p, p ) 7 Li, 7 Li (n, n ) 7 Li, and 7 Li (p, n ) 7 Be reactions was carried out by Presser and Bass [5].…”

Section: Introductionmentioning

confidence: 99%

Reactions leading to the first excited states ofLi7andBe7and isospin-mixed states in
Austin
¹
,
Paul
²
,
Brown
³

et al. 2019
Phys. Rev. C
1
0
0
0
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Background Ratios of cross sections for mirror reactions sometimes deviate from the values expected on the basis of charge symmetry. These deviations are attributed to smoothly varying charge dependent effects (proton charge, different Q values) and to the effects of isospin mixed states in the compound nucleus. The effects are large and well known for certain positive parity states in 8 Be, but information is lacking for negative parity states.Purpose To measure the excitation functions of angle integrated cross sections for two pairs of reactions that involve 8 Be as an intermediate state:(1) 6 Li (d, p ) 7 Li (0.478 MeV) and 6 Li (d, n ) 7 Be (0.429 MeV); (2) 7 Li (p, p ) 7 Li (0.478 MeV) and 7 Li (p, n ) 7 Be (0.429 MeV). To measure the ratios of the neutron emitting and proton emitting reactions. To examine the implications for the structure of 8 Be.Method The ratios were determined by observing the isotropically emitted gamma rays from the decay of 7 Li (0.478 MeV) and 7 Be (0.429 MeV). Shell model calculations were performed for both positive and negative parity states. Results were compared to existing information.Results Ratios, usually with an accuracy of ±2%, were obtained for deuteron energies from 0.15 to 7.2 MeV and proton energies from 3.0 to 10.0 MeV. There were relatively strong deviations from expectations based on charge symmetry at the lowest deuteron energies and smaller deviations between E d = 2 and 4 MeV. There were very strong deviations for proton energies near 3 and 5.5 MeV, with strong neutron strength near 3 MeV and strong proton strength near 5 MeV. The shell model calculations were generally in good agreement for the positive parity states, and, with some exceptions, for negative parity states. There is reasonable evidence for the lowest lying 2 − T = 1 state at Ex= 20.3 MeV and for two new isospin mixed pairs, one for 2 + states near 22 MeV and another for 2 − states near 24 MeV.Conclusions The results will constrain future calculations for isospin mixed states in 8 Be.PACS numbers: 26.20.Fj, 26.30.Jk, 26.50.+x

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Comparison of 6Li(d, n1) 7Be AND 6Li(d, p1) 7Li mirror reactions at low energies

Cited by 16 publications

References 15 publications

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

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

Oppenheimer-Phillips effect and electron screening ind+ d fusion reactions

Reactions leading to the first excited states ofLi7andBe7and isospin-mixed states in
Austin
¹
,
Paul
²
,
Brown
³

et al. 2019
Phys. Rev. C
1
0
0
0
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Comparison of 6Li(d, n1) 7Be AND 6Li(d, p1) 7Li mirror reactions at low energies

Cited by 16 publications

References 15 publications

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

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

Oppenheimer-Phillips effect and electron screening ind+ d fusion reactions

Reactions leading to the first excited states ofLi7andBe7and isospin-mixed states inAustin1, Paul2, Brown3 et al. 2019Phys. Rev. C1000View full textAdd to dashboardCite

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Reactions leading to the first excited states ofLi7andBe7and isospin-mixed states in
Austin
¹
,
Paul
²
,
Brown
³

et al. 2019
Phys. Rev. C
1
0
0
0
View full text Add to dashboard Cite