0000000000185597
AUTHOR
Andreas Stolz
New developments on the recoil distance doppler-shift method
Absolute transition probabilities are fundamental observables for nuclear structure. The recoil-distance-Doppler-shift (RDDS) technique, also called plunger technique, is a well established tool for the determination of these important experimental quantities via the measurement of lifetimes of excited nuclear states. Nowadays nuclear structure investigations are concentrated on exotic nuclei which are often produced with extremely small cross sections or with very low beam intensities. In order to use the RDDS technique also for the investigation of very exotic nuclei this method has to be adapted to the specific needs of these special reactions. This article gives an overview on recent RD…
β-decay measurements ofA≃ 70 − 110 r-process nuclei at the National Superconducting Cyclotron Laboratory
The present paper reports on several r-process motivated β-decay experiments undertaken at the National Superconducting Cyclotron Laboratory. β-decay half-lives and β-delayed neutron-emission probabilities were measured for nuclei around the r-process A = 70–80 and A = 90 – 110 mass regions. The data are discussed on the basis of quasi-random phase approximation calculations. The emphasis is made on the impact of these data upon calculations of r-process abundances.
Radioactive ion beams in the region of 100Sn and 78Ni at the NSCL
The regions around the doubly magic nuclei 100 Sn and 78 Ni are of great interest from a nuclear structure standpoint. These nuclei also play a key role in the astrophysical rp- and r-processes, respectively. Recently, nuclei in these regions were studied at the Coupled Cyclotron Facility at the National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University.
β-decay half-lives andβ-delayed neutron emission probabilities of nuclei in the regionA≲110, relevant for the r process
Measurements of $\ensuremath{\beta}$-decay properties of $A\ensuremath{\lesssim}110$ r-process nuclei have been completed at the National Superconducting Cyclotron Laboratory at Michigan State University. $\ensuremath{\beta}$-decay half-lives for $^{105}\mathrm{Y}$, $^{106,107}\mathrm{Zr}$, and $^{111}\mathrm{Mo}$, along with $\ensuremath{\beta}$-delayed neutron emission probabilities of $^{104}\mathrm{Y}$, $^{109,110}\mathrm{Mo}$ and upper limits for $^{105}\mathrm{Y}$, $^{103\ensuremath{-}107}\mathrm{Zr}$, and $^{108,111}\mathrm{Mo}$ have been measured for the first time. Studies on the basis of the quasi-random-phase approximation are used to analyze the ground-state deformation of these…
β-Decay Studies Close to the N=82 r-process Path
New half-lives for neutron-rich ruthenium, rhodium and palladium isotopes close to the r-process path along the N=82 closed shell have been measured at the National Superconducting Cyclotron Laboratory at Michigan State University. The studied isotopes are close to the critical A=118-126 mass region in the astrophysical r-process, where incorrect nuclear structure development towards the shell closure may have the most pronounced effect on the abundances of elements produced. Neutron-rich nuclei were produced by fragmentation of a 120-MeV per nucleon 136 Xe beam on Be and were separated by the A1900 fragment separator. The nuclei of interest were implanted into a double-sided Si strip detec…
Superallowed Gamow-Teller decay of the doubly magic nucleus $^{100}$Sn
Expérience au GSI; The shell structure of atomic nuclei is associated with 'magic numbers' and originates in the nearly independent motion of neutrons and protons in a mean potential generated by all nucleons. During b1-decay, a proton transforms into a neutron in a previously not fully occupied orbital, emitting a positron-neutrino pair with either parallel or antiparallel spins, in a Gamow-Teller or Fermi transition, respectively. The transition probability, or strength, of a Gamow-Teller transition depends sensitively on the underlying shell structure and is usually distributed among many states in the neighbouring nucleus. Here we report measurements of the half-life and decay energy fo…
Nucleosynthesis of proton-rich nuclei. Experimental results on the rp-process
Experience NSCL; International audience; We report in this study the nuclear properties of proton-rich isotopes located along the rp-process path. The experiments have recently been performed at the National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University. The level properties above the proton separation energy of the nuclei 30S, 36K and 37Ca were measured with precision of < 10 keV. This will allow a reduction in the determination of the astrophysical (p, ) reaction rate under rp-process conditions.
Half-Life of the Doubly Magicr-Process NucleusN78i
Nuclei with magic numbers serve as important benchmarks in nuclear theory. In addition, neutron-rich nuclei play an important role in the astrophysical rapid neutron-capture process (r process). 78Ni is the only doubly magic nucleus that is also an important waiting point in the r process, and serves as a major bottleneck in the synthesis of heavier elements. The half-life of 78Ni has been experimentally deduced for the first time at the Coupled Cyclotron Facility of the National Superconducting Cyclotron Laboratory at Michigan State University, and was found to be 110(+100)(-60) ms. In the same experiment, a first half-life was deduced for 77Ni of 128(+27)(-33) ms, and more precise half-li…