Alpha-cluster Condensations in Nuclei and Experimental Approaches for their Studies

The formation of alpha-clusters in nuclei close to the decay thresholds is discussed. These states can be considered to be boson-condensates, which are formed in a second order phase transition in a mixture of nucleons and alpha-particles. The de Broglie wavelength of the alpha-particles is larger than the nuclear diameter, therefore the coherent properties of the alpha-particles give particular effects for the study of such states. The states are above the thresholds thus the enhanced emission of multiple-alphas into the same direction is observed. The probability for the emission of multiple-alphas is not described by Hauser-Feshbach theory for compound nucleus decay.Comment: 21 pages, 12 figures

Approaching the Gamow Window with Stored Ions : Direct Measurement of Xe 124 (p,γ) in the ESR Storage Ring

© 2019 American Physical Society. All rights reserved.We report the first measurement of low-energy proton-capture cross sections of Xe124 in a heavy-ion storage ring. Xe12454+ ions of five different beam energies between 5.5 and 8 AMeV were stored to collide with a windowless hydrogen target. The Cs125 reaction products were directly detected. The interaction energies are located on the high energy tail of the Gamow window for hot, explosive scenarios such as supernovae and x-ray binaries. The results serve as an important test of predicted astrophysical reaction rates in this mass range. Good agreement in the prediction of the astrophysically important proton width at low energy is found, with only a 30% difference between measurement and theory. Larger deviations are found above the neutron emission threshold, where also neutron and γ widths significantly impact the cross sections. The newly established experimental method is a very powerful tool to investigate nuclear reactions on rare ion beams at low center-of-mass energies.Peer reviewedFinal Published versio

New test of modulated electron capture decay of hydrogen-like 142Pm ions: Precision measurement of purely exponential decay

An experiment addressing electron capture (EC) decay of hydrogen-like 142Pm60+ions has been conducted at the experimental storage ring (ESR) at GSI. The decay appears to be purely exponential and no modulations were observed. Decay times for about 9000 individual EC decays have been measured by applying the single-ion decay spectroscopy method. Both visually and automatically analysed data can be described by a single exponential decay with decay constants of 0.0126(7)s−1for automatic analysis and 0.0141(7)s−1for manual analysis. If a modulation superimposed on the exponential decay curve is assumed, the best fit gives a modulation amplitude of merely 0.019(15), which is compatible with zero and by 4.9 standard deviations smaller than in the original observation which had an amplitude of 0.23(4)

Transition from collectivity to single-particle degrees of freedom from magnetic moment measurements on 38 82 Sr 44 and 38 90 Sr 52

International audienc

Proton and α capture studies for nuclear astrophysics at GSI storage rings

The 124Xe(p,γ) reaction has been measured for the first time at energies around the Gamow window by using stored ions at the ESR facility. The desired beam energies below 10 MeV/u introduce new experimental challenges like windowless ions detection under UHV conditions, extremely short beam lifetimes and efficient beam deceleration and cooling, all of which have been successfully met

Half-life measurements of highly charged radionuclides

16th International Conference on the Physics of Highly Charged Ions (HCI), Ruprecht Karls Univ, Heidelberg, GERMANY, SEP 02-07, 2012International audienceIn recent years several measurements of the orbital electron capture half-lives of few-electron ions have been carried out employing the storage ring ESR at GSI. Hydrogen-like and helium-like Pr-140 and Pm-142 as well as hydrogen-like I-122 were studied. Half-lives of the corresponding fully ionized nuclides provide the three-body beta(+) decay constants

Studies at the border between nuclear and atomic physics: Weak decays of highly charged ions

Present status of experimental studies of weak decays of highly charged ions is presented. The paper closely follows the progress-report presentation given at the conference. Due to the limited space an emphasis is given to an exhaustive bibliography