G. Gyürky

Enhanced electron screening in d(d, p)t for deuterated Ta

Abstract:The recent observation of a large electron screening effect in the d(d, p)t reaction using a deuterated Ta target has been confirmed using somewhat different experimental approaches: Ue = 309±12 eV for the electron screening potential energy. The high Ue value arises from the environment of the deuterons in the Ta matrix, but a quantitative explanation is missing.

First measurement of the 14N(p,γ)15O cross section down to 70 keV

Abstract In stars with temperatures above 20 × 10 6 K , hydrogen burning is dominated by the CNO cycle. Its rate is determined by the slowest process, the 14N(p, γ)15O reaction. Deep underground in Italys Gran Sasso laboratory, at the LUNA 400 kV accelerator, the cross section of this reaction has been measured at energies much lower than ever achieved before. Using a windowless gas target and a 4π BGO summing detector, direct cross section data has been obtained down to 70 keV, reaching a value of 0.24 picobarn. The Gamow peak has been covered by experimental data for several scenarios of stable and explosive hydrogen burning. In addition, the strength of the 259 keV resonance has been remeasured. The thermonuclear reaction rate has been calculated for temperatures 90 – 300 × 10 6 K , for the first time with negligible impact from extrapolations.

Electron screening in d(d, p)t for deuterated metals and the periodic table ✩

The electron screening effect in the d(d, p)t reaction has been studied for 29 deuterated metals and 5 deuterated insulators/semiconductors. As compared to measurements performed with a gaseous D2 target, a large effect has been observed in the metals V, Nb, and Ta, which belong to group 5 of the periodic table, as well as in Cr, Mo, and W (group 6), Mn and Re (group 7), Fe and Ru (group 8), Co, Rh, and Ir (group 9), Ni, Pd, and Pt (group 10), Zn and Cd (group 12), and Sn and Pb (group 14). In contrast, a comparatively small effect is found in group 4 (Ti, Zr, Hf), group 11 (Cu, Ag, Au), group 13 (B, Al), for the insulator BeO, and for the semiconductors C, Si, and Ge. An explanation of this apparently novel feature of the periodic table is missing.  2002 Elsevier Science B.V. All rights reserved.

Electron screening effect in the reactions 3 He(d, p) 4 He and d( 3 He, p) 4 He ☆ ☆ Supported in part by INFN, BMBF (06BO812), DFG (436UNG113-146) and OTKA (T025465).

The cross section of the reactions 3He(d, p)4He and d(3He, p)4He has been measured at the center-of-mass energies E=5 to 60 keV and 10 to 40 keV, respectively. The experiments were performed to determine the magnitude of the electron screening effect leading to the respective electron-screening potential energy Ue=219±7 and 109±9 eV, which are both significantly higher than the respective values from atomic physics models, Ue=120 and 65 eV.

A new setup for the underground study of capture reactions

For the study of astrophysically relevant capture reactions in the underground laboratory LUNA a newsetup of high sensitivity has been implemented. The setup includes a windowless gas target, a 4p BGO summing crystal, and beam calorimeters. The setup has been recently used to measure the d(p,g) 3 He cross-section for the first time within its solar Gamowpeak, i.e. dow n to 2.5 keV c.m. energy. The features of the optimized setup are described. r 2002 Elsevier Science B.V. All rights reserved.

IMPACT OF A REVISED 25Mg(p, γ)26Al REACTION RATE ON THE OPERATION OF THE Mg-Al CYCLE

Proton captures on Mg isotopes play an important role in the Mg-Al cycle active in stellar H-burning regions. In particular, low-energy nuclear resonances in the

The 25Mg(p, γ) 26Al reaction at low astrophysical energies

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Enhanced electron screening in d(d, p)t for deuterated metals: a possible classical explanation

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Electron screening in d(d, p)t for deuterated metals: temperature effects

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Precision study of ground state capture in the N-14(p, gamma)O-15 reaction

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