Cadmium mass measurements between the neutron shell closures at N=50 and 82
International audience; The mass values of the neutron-deficient cadmium isotopes 99−109Cd and of the neutronrich isotopes 114,120,122−124,126,128Cd have been measured using ISOLTRAP. The behavior of the separation energies of the cadmium isotopes from N = 50 to 82 is discussed.
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…
Development of a new Recoil Distance Technique using Coulomb Excitation in Inverse Kinematics
We report on an experiment using Coulomb excitation in inverse kinematics in combination with the plunger technique for measuring lifetimes of excited states of the projectiles. Aside from the investigation of E(5) features in 128Xe, the aim was to explore the special features of such experiments which are also suited to be used with radioactive beams. The measurement was performed at the JYFL with the Koln coincidence plunger device and the JUROGAM spectrometer using a 128Xe beam impinging on a natFe target at a beam energy of 525 MeV. Recoils were detected by means of 32 solar cells placed at extreme forward angles. Particle‐gated γ‐singles and γγ‐coincidences were measured at different t…
High accuracy [sup 18]O(p,α)[sup 15]N reaction rate in the 8⋅10[sup 6]–5⋅10[sup 9] K temperature range
The 18O(p,α)15N reaction is of great importance in several astrophysical scenarios, as it influences the production of key isotopes such as 19F, 18O and 15N. In this work, a high accuracy 18O(p,α)15N reaction rate is proposed, based on the simultaneous fit of direct measurements and of the results of a new Trojan Horse experiment. In particular, we have focused on the study of the broad 660 keV 1/2+ resonance. Since Γ∼100–300 keV, it strongly influences the nearly‐zero‐energy region of the cross section by means of the low‐energy tail of the resonant contribution and dominates the cross section at higher energies. Here we provide a factor of 2 larger reaction rate above T∼0.5 109 K based ov…
A Recoil-Beta Tagging Study of N = Z nucleus [sup 66]As
A Recoil‐Beta Tagging (RBT) experiment was recently performed at the accelerator laboratory at the University of Jyvaskyla in order to identify T = 1 excited states in the medium‐heavy N = Z = 33 nucleus 66As. The fusion‐evaporation reaction 28Si(40Ca,pn)66As was employed at a beam energy of 75 MeV. The experiment was carried out utilising the JUROGAM II γ‐ray spectrometer in conjunction with the gas‐filled recoil separator RITU and the GREAT focal plane spectrometer system. The half‐lives and ordering of the two known isomeric states in 66As have been determined. In addition, several new prompt γ‐ray transitions from excited states both bypassing and decaying to the isomeric states in 66As…
A new recoil distance technique using low energy coulomb excitation in inverse kinematics
Abstract We report on the first experiment combining the Recoil Distance Doppler Shift technique and multistep Coulomb excitation in inverse kinematics at beam energies of 3–10 A MeV. The setup involves a standard plunger device equipped with a degrader foil instead of the normally used stopper foil. An array of particle detectors is positioned at forward angles to detect target-like recoil nuclei which are used as a trigger to discriminate against excitations in the degrader foil. The method has been successfully applied to measure lifetimes in 128Xe and is suited to be a useful tool for experiments with radioactive ion beams.
Gamow-Teller Transitions Starting from T[sub z] = +3∕2 Nucleus [sup 47]Ti
Gamow‐Teller (GT) transitions are mediated by the στ operator. Owing to its simplicity and also its spin‐isospin nature, GT transitions play key roles in the studies of nuclear structure as well as astro‐nuclear processes. In violent neutrino‐induced reactions at the core‐collapse stage of type II supernovae, Gamow‐Teller (GT) transitions starting from stable as well as unstable pf‐shell nuclei play important roles. We study GT transitions starting from 47Ti in a high‐resolution (3He,t) charge‐exchange reactions at 0° and at an intermediate incident energy of 140 MeV/nucleon at Research Center for Nuclear Physics (RCNP), Osaka. Individual GT transitions up to high excitations were observed.…
A systematic study of proton capture reactions in the SeSb region at energies relevant to the p process
Abstract A systematic investigation of (p,γ) cross sections of nuclei from Se to Sb is presented. In-beam cross section measurements were carried out at E p = 1.4–5 MeV by using an array of 4 HPGe detectors of 100% relative efficiency shielded with BGO crystals. The S factors obtained are compared with the predictions of the statistical model code MOST.
Plunger Lifetime Measurements in 102Pd
Recently, an intense experimental effort has been devoted to the search of empirical proofs of critical‐point symmetries in nuclear structure. These symmetries describe shape‐phase transitions and provide parameter‐free predictions (up to over‐all scale factors) for excitation spectra and B(E2) values. This contribution reports on recent plunger‐lifetime measurements ON 102Pd carried out at LNL, Legnaro, with the Cologne plunger apparatus coupled to the GASP spectrometer and using the 92Zr(13C,3n)102Pd reaction at 48 MeV. According to the results of our measurements, 102Pd is so far the best known paradigm of the E(5) critical‐point symmetry.
FINITE-RANGE SEPARABLE PAIRING INTERACTION WITHIN NEW N[sup 3]LO DFT APPROACH
For over four decades, the Skyrme functional within various parametrizations has been used to calculate nuclear properties. In the last few years there was a number of attempts to improve its performance and introduce generalized forms. In particular, the most general phenomenologi‐cal quasi‐local energy density functional, which contains all combinations of density, spin‐density, and their derivatives up to the sixth order (N3LO), was proposed in reference [1]. Since in the phe‐nomenological functional approaches the particle‐particle (pp) interaction channel is treated independently from the particle‐hole (ph) channel, there remains a question of what pairing interaction is suitable to us…
The key reactions in Stellar helium burning: 12C(α,γ)16O and 22Ne(α,n)25Mg
Abstract The excitation functions of 12C(α,γ)16O and 22Ne(α,n)25Mg have been determined with a yet unequaled experimental sensitivity of 10−11 b. From γ-angular distributions the SE1-and SE2-factors for 12C(α,γ)16O have been deduced and extrapolated into the range of helium burning temperatures using the R-matrix method. An improved reaction rate has been calculated: NA〈σν〉=(7.9±2.5)x10−15cm3(mols)−1 at T9 = 0.2. For a more precise extrapolation the excitation function has to be measured with better statistics. Therefore a new experiment on 12C(α,γ)16O with a better suited setup has been started recently. The accuracy of the 22Ne(α,n)25Mg reaction rate could be improved considerably compare…
Systematic measurements of proton- and alpha-capture cross sections relevant to the modelling of the p process
Several in-beam cross section measurements of proton- as well as α -capture reactions in the Se-Sb region have been carried out to obtain global input parameters for Hauser-Feshbach (HF) calculations. In total, 20 (p, γ ) and 7 ( α , γ ) reactions were measured. We compare some of these results with Hauser-Feshbach calculations using various optical model potentials and nuclear level densities.
TAS measurements for reactor physics and nuclear structure
In this contribution we will present recent total absorption measurements of the beta decay of neutron‐rich nuclei performed at the IGISOL facility of the Univ. of Jyvaskyla. In the measurements the JYFL Penning Trap was used as a high resolution isobaric separator. The total absorption technique will be described and the impact of recent results in the fields of reactor physics (decay heat calculations) and nuclear structure will be discussed.
Proton and alpha-particle capture reactions at sub-Coulomb energies relevant to the p process
Several cross-section measurements of proton as well as α-particle capture reactions in the Se–Sb region have been carried out at sub-Coulomb energies with the aim to obtain global input parameters for Hauser–Feshbach (HF) calculations. Some of the results are compared with HF calculations using various optical model potentials and nuclear level densities.