F. J. Bergmeister

Bio: F. J. Bergmeister is an academic researcher from University of Göttingen. The author has contributed to research in topics: Resonance & Hyperfine structure. The author has an hindex of 3, co-authored 4 publications receiving 306 citations. Previous affiliations of F. J. Bergmeister include University of Cologne.

Energy calibration of the 500 kV heavy ion implanter ionas

Abstract: Gamma ray yield functions of (p, αγ) and (p, γ) resonance reactions on semi-thick 19F, 23Na, 24,26Mg and 27Al targets were measured and used to calibrate the accelerating voltage and energy resolution of the new 500 kV heavy ion implanter at Gottingen. The energy spread of the proton beam was found to vary linearly with the accelerating voltage from ΔE(200 keV) = 55 eV fwhm to ΔE(500 keV) = 105 eV; it is made up by a 0.012% high voltage ripple and the Doppler broadening of the resonances due to the thermal motion of the target nuclei. A long term stability of the proton energy of Applications of the accelerator for the remeasurement of some resonance energies and widths and for depth profiling of light implanted ions in metals by the resonance broadening method will be briefly discussed.

Note on stellar26Al production via the25Mg(p, γ) process

Abstract: Resonance energies and widths of four resonances in the reaction25Mg(p,γ)26Al were measured with the high resolution proton beam of the new 500 kV accelerator IONAS. The previously given large width of the 389 keV resonance, Γ= 460±70 eV. (1), used in the interpretation of stellar26A1 production was shown to be incorrect and probably caused by target oxidation effects and insufficient energy resolution of the beam. The new value is Γ<4 eV.

Magnetic hyperfine interaction of 41 Ca and 41 K nuclei implanted into iron

Abstract: Time integral and time differential measurements of the perturbed angular distribution of γ-ray transitions following the decays of the 3.83 MeV state in41Ca and the 1.29 MeV state in41K have been performed; the nuclei have been recoil implanted into magnetized iron foils after heavy ion reactions. A consistent description of the present and previous PAD and channeling data is obtained. In the system CaFe, the magnetic hyperfine field follows the bulk magnetization. In the system KFe, three fractions associated with different hyperfine fields are proposed which also account for the annealing behaviour and rapid loss of alignment observed.

Magnetic hyperfine interaction of swift43 K ions recoiling in helium and xenon

Abstract: The 738 keV 7/2− isomeric state in43K (Τ=292 ± 5 ns,g=1.266 ± 0.015) was produced in the reaction4He(40Ar,p) using the 185 MeV pulsed40Ar beam of VICKSI and a 2–7 bar helium target cell. The suitability of this isomeric state for hyperfine studies during recoil in gases and after implantation into solids was investigated via the TDPAD technique. The hyperfine deorientation of highly stripped43K ions in He and Xe was investigated and interpreted with the AbragamPound model. When adding up to 15% Xe to the He target gas, a near-exponential loss of alignment with the Xe partial pressure was observed. This effect can be explained by K-hole production in43K in the Xe-K collision for which a cross section ofσ=5 · 10−18 cm2 was estimated.

Superallowed 0 + →0 + nuclear β decays: A new survey with precision tests of the conserved vector current hypothesis and the standard model

Abstract: A new critical survey is presented of all half-life, decay-energy, and branching-ratio measurements related to 20 superallowed ${0}^{+}\ensuremath{\rightarrow}{0}^{+}\ensuremath{\beta}$ decays. Compared with our last review, there are numerous improvements: First, we have added 27 recently published measurements and eliminated 9 references, either because they have been superseded by much more precise modern results or because there are now reasons to consider them fatally flawed; of particular importance, the new data include a number of high-precision Penning-trap measurements of decay energies. Second, we have used the recently improved isospin symmetry-breaking corrections, which were motivated by these new Penning-trap results. Third, our calculation of the statistical rate function $f$ now accounts for possible excitation in the daughter atom, a small effect but one that merits inclusion at the present level of experimental precision. Finally, we have re-examined the systematic uncertainty associated with the isospin symmetry-breaking corrections by evaluating the radial-overlap correction using Hartree-Fock radial wave functions and comparing the results with our earlier calculations, which used Saxon-Woods wave functions; the provision for systematic uncertainty has been changed as a consequence. The new ``corrected'' $\mathcal{F}t$ values are impressively constant and their average, when combined with the muon lifetime, yields the up-down quark-mixing element of the Cabibbo-Kobayashi-Maskawa (CKM) matrix, ${V}_{\mathit{ud}}=0.97425\ifmmode\pm\else\textpm\fi{}0.00022$. The unitarity test on the top row of the matrix becomes $|{V}_{\mathit{ud}}|{}^{2}+|{V}_{\mathit{us}}|{}^{2}+|{V}_{\mathit{ub}}|{}^{2}=0.99995\ifmmode\pm\else\textpm\fi{}0.00061$. Both ${V}_{\mathit{ud}}$ and the unitarity sum have significantly reduced uncertainties compared with our previous survey, although the new value of ${V}_{\mathit{ud}}$ is statistically consistent with the old one. From these data we also set limits on the possible existence of scalar interactions, right-hand currents, and extra $Z$ bosons. Finally, we discuss the priorities for future theoretical and experimental work with the goal of making the CKM unitarity test even more definitive.

The LUNA II 400 kV accelerator

Abstract: A second high current accelerator of 400 kV has been installed at the underground laboratory of Gran Sasso, called LUNA II. We describe this new facility as well as measurements of the proton beam characteristics: absolute energy, energy spread, and long-term energy stability. The absolute energy was determined to a precision of 7300 eV at Ep ¼ 130–400 keV using the energy of the capture g-ray transition of 12 Cðp;gÞ 13 N as well as resonance energies at Ep ¼ 309–389 keV of 23 Naðp;gÞ 24 Mg; 26 Mgðp;gÞ 27 Al; and 25 Mgðp;gÞ 26 Al: The resonance studies led to a proton energy