The Coulomb phase shift revisited

We investigate the Coulomb phase shift, and derive and analyze new and more precise analytical formulae. We consider next to leading order terms to the Stirling approximation, and show that they are important at small values of the angular momentum $l$ and other regimes. We employ the uniform approximation. The use of our expressions in low energy scattering of charged particles is discussed and some comparisons are made with other approximation methods.Comment: 13 pages, 5 figures, 1 tabl

Nuclear Structure Relevant to Neutrinoless Double Beta Decay: 76Ge and 76Se

The possibility of observing neutrinoless double beta decay offers the opportunity of determining the neutrino mass IF the nuclear matrix element were known. Theoretical calculations are uncertain and measurements of the occupations of valence orbits by nucleons active in the decay can be important. The occupation of valence neutron orbits in the ground states of 76Ge and 76Se were determined by precisely measuring cross sections for both neutron-adding and removing transfer reactions. Our results indicate that the Fermi surface is much more diffuse than in theoretical (QRPA) calculations. We find that the populations of at least three orbits change significantly between these two ground states while in the calculations the changes are confined primarily to one orbit.Comment: 4 pages, 3 figure

High-precision mass measurement of Sn103 restores smoothness of the mass surface

As a step towards the ultimate goal of a high-precision mass measurement of doubly magic Sn100, the mass of Sn103 was measured at the Low Energy Beam and Ion Trap (LEBIT) located at the Facility for Rare Isotope Beams (FRIB). Utilizing the time-of-flight ion cyclotron resonance technique, a mass uncertainty of 3.7 keV was achieved, an improvement by more than an order of magnitude compared to a recent measurement performed in 2023 at the Cooler Storage Ring (CSRe) in Lanzhou. Although the LEBIT and CSRe mass measurements of Sn103 are in agreement, they diverge from the experimental mass value reported in the 2016 version of the Atomic Mass Evaluation (AME2016), which was derived from the measured Qβ+ value and the mass of In103. In AME2020, this indirectly measured Sn103 mass was classified as a "seriously irregular mass"and replaced with an extrapolated value, which aligns with the most recent measured values from CSRe and LEBIT. As such, the smoothness of the mass surface is confidently reestablished for Sn103. Furthermore, LEBIT's mass measurement of Sn103 enabled a significant reduction in the mass uncertainties of five parent isotopes which are now dominated by uncertainties in their respective Q values

Nuclear structure relevant to neutrinoless double β decay: Ge76 and Se76

The possibility of observing neutrinoless double β decay offers the opportunity of determining the effective neutrino mass if the nuclear matrix element were known. Theoretical calculations are uncertain, and measurements of the occupations of valence orbits by nucleons active in the decay can be important. The occupation of valence neutron orbits in the ground states of Ge76 (a candidate for such decay) and Se76 (the daughter nucleus) were determined by precisely measuring cross sections for both neutron-adding and removing transfer reactions. Our results indicate that the Fermi surface is much more diffuse than in theoretical calculations. We find that the populations of at least three orbits change significantly between these two ground states while in the calculations, the changes are confined primarily to one orbit. © 2008 The American Physical Society

Atomic effects in heavy-ion elastic scattering

Angular distributions of a Pb-208 beam on Pb-208 thin targets at very small angles were measured. The shape of the experimental distribution is not Gaussian, indicating a plural scattering regime rather than multiple scattering. The distribution was well reproduced by a Monte Carlo simulation of the straggling process. For the first time we observed and quantified the influence of the production of electrons during the scattering. This effect was observed in the angular correlation of the scattered Pb-208 nuclei detected in kinematic coincidence and also in the limiting angle of the Pb-208 scattered in a Ag-107,Ag-109 target. This effect introduces a spread in the scattered angle which is of the same order of magnitude as the angular straggling

SEARCH FOR COLOR VAN-DER-WAALS FORCE IN PB-208+PB-208 MOTT SCATTERING

In a high precision experiment, Mott scattering of the Pb-208 + Pb-208 system was measured at E(lab) = 873.40 MeV and 1129.74 MeV with kinematic coincidences for angle pairs around theta(lab) = 30-degrees, 60-degrees and theta(lab) = 45-degrees, 45-degrees. The observed Mott oscillations exhibit an angular shift with respect to pure Mott scattering. A comparison with the angular shift produced by a color van der Waals force including nuclear polarizability, vacuum polarization, relativistic effects, and electronic screening provides a new upper limit for the strength of this force. Influence of atomic effects other than screening were identified for the first time