Accelerator Experiments and Theoretical Models for the Electron Screening Effect in Metallic Environments

Huke, A.; Czerski, K.; Heide, P.

doi:10.1142/9789812774354_0014

Cited by 3 publications

(3 citation statements)

References 19 publications

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“…Thus, the small value of U e = 80 ± 20 eV obtained for Zr and some other metals [10], being significantly smaller than both our experimental and theoretical values, might be due to the re-oxidation process of the target. Since the main goal of the present paper is a theoretical one, we refer for a detailed discussion of experimental results to our forthcoming paper [28]. Certainly, future experiments performed under ultra-high vacuum conditions will allow to clear the discrepancy.…”

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“…From a theoretical point of view, the experiments performed with deuterized metals provide information about the electron screening not only due to bound electrons as is the case for gas-phase experiments, but also about a contribution arising from free metallic electrons. The latter gives us a possibility to test models of the electron screening based on the dielectric function theory which describes the electronic dynamics in solids [11] as well as in dense astrophysical plasmas [28]. Here, we compare our previously published [4] and some new experimental data with the results of an improved theoretical approach including the self-consistent correction of the dielectric function.…”

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confidence: 99%

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The ² H(d,p) ³ H reaction in metallic media at very low energies

Czerski

Huke²,

Heide³

et al. 2004

Europhys. Lett.

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Abstract. -Based on our experimental studies of the electron screening effect in the 2 H(d, p) 3 H reaction for five deuteron-implanted solid targets (C, Al, Zr, Pd, Ta), theoretical calculations have been performed within an improved dielectric function theory. The theory describes correctly the observed target material dependence of the screening energies, underestimating, however, the absolute values by about a factor of 2. Applying an effective screening energy approach, the theoretical cross-sections, thick-target yields as well as nuclear reaction rates have been calculated down to the energies corresponding to the conditions of so-called cold-fusion experiments. This allows for a comparison of the experimental results at higher energies with those achieved in the heavy-water electrolysis experiments.Introduction. -Nuclear reaction rates at very low projectile energies, far below the Coulomb barrier, are sensitive to the electronic properties of target materials. The electrons surrounding the reacting nuclei can increase the tunneling probability through the Coulomb barrier leading to an enhancement of nuclear reaction rates at low projectile energies. The electron screening effect was originally discussed due to its importance for dense astrophysical plasmas, where nuclear reaction rates can be increased by many orders of magnitudes [1]. Experimentally, the screening effect could be verified only fifteen years ago in gas target experiments [2] by an observation of an exponential-like increase of the measured cross-section for decreasing projectile energies compared to the cross-section expected for bare nuclei. Theoretically, this effect was described [3] by applying a conception of the electron screening energy resulting from the gain in the electron binding energy between the initially separated atoms and the finally united atom. In the experiments, the screening energy could be treated as an energy shift of the kinetic energy of the reacting nuclei causing an increase of the penetration probability through the Coulomb barrier.

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The ² H(d,p) ³ H reaction in metallic media at very low energies

Czerski

Huke²,

Heide³

et al. 2004

Europhys. Lett.

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“…The targets were pure metal disks becoming self-implanted deuterium targets under the deuteron irradiation. Four Si-detectors at the laboratory angles of 90¢ , 110¢ , 130¢ and 150¢ were used for the detection of all charged particles, p, t, 3 He, of the reactions 2 H(d,p)t and 2 H(d,n) 3 He [6,2]. The detectors needed to be shielded from the backscattered deuterons in order to prevent a congestion of them and the data acquisition system.…”

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EVIDENCE FOR A TARGET-MATERIAL DEPENDENCE OF THE NEUTRON–PROTON BRANCHING RATIO IN d + d REACTIONS FOR DEUTERON ENERGIES BELOW 20 keV

Huke

Czerski

Dorsch

et al. 2006

Condensed Matter Nuclear Science

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Angular distributions and the neutron-proton branching ratio of the mirror reactions 2 H(d,p) 3 H and 2 H(d,n) 3 He have been investigated using different deuterized metallic targets at projectile energies ranging from 5 to 60 keV. Whereas the experimental results obtained for Al, Zr, Pd and Ta targets do not differ from those known from gas-target experiments, an enhancement of the angular anisotropy in the neutron channel and a quenching of the neutron-proton branching ratio have been observed for Li and Sr targets at deuteron energies below 20 keV . Both effects can be explained assuming an induced adiabatic polarization of the reacting deuterons in the crystal lattice.

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