Energy loss, electron screening and the astrophysical 3He(d, p)4He cross section

Langanke, K.; Shoppa, T. D.; Barnes, C. A.; Rolfs, C.

doi:10.1016/0370-2693(96)00066-4

Cited by 52 publications

(51 citation statements)

References 11 publications

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“…The experimental investigations of the last decade were focused on gas target studies [3] which, however, can include only the bound electron contribution to the screening energy. The experimental and theoretical values for U e were found to be in reasonable agreement; discrepancies in some cases could be removed by means of corrections of the projectile stopping power values [4] or a better understanding of the reaction mechanism in the vicinity of the reaction threshold [5]. From both d+d fusion reactions…”

Section: E S(e)e −2πη(e)mentioning

confidence: 70%

Enhancement of the electron screening effect for d + d fusion reactions in metallic environments

et al. 2001

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Abstract. -To study the electron screening of nuclear reactions in metallic environments, angular distributions and thick target yields of the fusion reactions 2 H(d,p) 3 H and 2 H(d,n) 3 He have been measured on deuterons implanted in three different metal targets (Al, Zr and Ta) for beam energies ranging from 5 to 60 keV. The experimentally determined values of the screening energy are about one order of magnitude larger than the value achieved in a gas target experiment and significantly larger than the theoretical predictions. A clear target material dependence of the screening energy has been established.Introduction. -At sufficiently low projectile energies an enhancement of the cross-section for charged-particle-induced nuclear reactions can be observed. This is due to the shielding of the charges of reacting nuclei by surrounding electrons which leads to an increase of the Coulomb barrier penetrability and enhances the measured cross-section in comparison to the bare nuclei case. This effect, known as electron screening, was originally discussed for the dense plasma in the interior of stars [1], where, due to screening, the nuclear-reaction rates can be increased by many orders of magnitude. For laboratory thermonuclear reactions, the screening effect was predicted [2] and experimentally verified for several light nuclear systems [3].In the simplest picture, the enhancement of the cross-section results from the gain of electronic binding energy (called screening energy U e ) which can be transferred to the relative motion of the colliding nuclei. In an adiabatic limit, i.e. with velocities v nuclear v electron , this energy shift can be treated as constant. Consequently, the enhancement factor f defined as the ratio between the cross-sections for screened and bare nuclei can be calculated as follows [2]:

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Section: E S(e)e −2πη(e)mentioning

confidence: 70%

Enhancement of the electron screening effect for d + d fusion reactions in metallic environments

et al. 2001

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“…A possible solution of the laboratory screening problem was proposed [14,15]. Experimentalists often use the extrapolation of stopping power tables [16] to obtain the average value of the projectile energy due to stopping in the target material.…”

Section: Nuclear Reactionsmentioning

confidence: 99%

“…The reaction studied is 9 Be( 15 C, 14 C gs ). The total cross sections as a function of the bombarding energy are shown in figures 7.…”

Section: Knock-out Reactionsmentioning

confidence: 99%

Theory of the Coulomb Dissociation

Bertulani¹

2013

Proceedings of VI European Summer School on Experimental Nuclear Astrophysics — PoS(ENAS 6)

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We observe photons and neutrinos from stars. Based on these observations, complemented by measurements of cosmic rays energies and composition, we have been able to constrain several models for the Big Bang and for stellar evolution. But that is not enough. We also need to help this effort with laboratory experiments. We are still far from being able to reproduce stellar environments in a terrestrial laboratory. But in many cases we can obtain accurate nuclear reaction rates needed for modeling primordial nucleosynthesis and hydrostatic burning in stars. The relevant reactions are difficult to measure directly in the laboratory at the small astrophysical energies. In recent years indirect reaction methods have been developed and applied to extract low-energy astrophysical S-factors. These methods require a combination of new experimental techniques and theoretical efforts, which are the subject of this short review.

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“…It has also been recently observed that in the reactions of light nuclei at very low energies, e.g. d + 3 He, the cross section depends on whether one uses an atomic deuteron beam or a molecular deuterium target (Broggini et al 1994;Langanke et al 1996). The reason for this is that at very low energies the screening effects of the electrons have a major effect on the tunnelling probability.…”

Section: Recent Developmentsmentioning

confidence: 99%

Tunnelling in the Presence of an Environment: Insights from the Fusion of Heavy Nuclei

Rowley

1997

Aust. J. Phys.

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A great many physical processes are mediated by the penetration or surmounting of a potential barrier. Some notable examples are the thermionic emission of electrons, chemical reactions, tunnelling of Cooper pairs through Josephson junctions, nuclear ‘burning’ in stars etc. Often the potential in question is not simply a function of the position of the intruding particle, but is a complicated landscape determined by the static structure of the physical objects concerned as well as by their dynamical response to their mutual interactions. For example, in a Josephson junction, the penetration of the barrier is strongly influenced by the excitation of lattice vibrations while catalysed chemical reactions proceed via complex routes which present a series of lower activation energies. In a physical system with a well-defined temperature, the details of the potential landscape may be obscured by the Maxwell-Boltzmann distribution of energies. The fusion of heavy nuclei can, however, be achieved over a controlled range of well-defined beam energies to reveal fine details of some of these effects. To date the major new experimental work in this area has been performed at the ANU, Canberra and at the INFN, Legnaro. As well as yielding valuable information on nuclear structure (detailed information on nuclear shapes etc.) and some totally unexpected reaction dynamics (complexity of the induced surface oscillations, neutron flow), these experiments and their theoretical analysis give considerable insights into the general problem of ‘tunnelling in the presence of an environment’.

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Energy loss, electron screening and the astrophysical 3He(d, p)4He cross section

Cited by 52 publications

References 11 publications

Enhancement of the electron screening effect for d + d fusion reactions in metallic environments

Enhancement of the electron screening effect for d + d fusion reactions in metallic environments

Theory of the Coulomb Dissociation

Tunnelling in the Presence of an Environment: Insights from the Fusion of Heavy Nuclei

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