0000000000951924
AUTHOR
D. L. Balabanski
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.
Simple Nuclear Structure inCd111–129from Atomic Isomer Shifts
Isomer shifts have been determined in ^{111-129}Cd by high-resolution laser spectroscopy at CERN-ISOLDE. The corresponding mean square charge-radii changes, from the 1/2^{+} and the 3/2^{+} ground states to the 11/2^{-} isomers, have been found to follow a distinct parabolic dependence as a function of the atomic mass number. Since the isomers have been previously associated with simplicity due to the linear mass dependence of their quadrupole moments, the regularity of the isomer shifts suggests a higher order of symmetry affecting the ground states in addition. A comprehensive description assuming nuclear deformation is found to accurately reproduce the radii differences in conjunction wi…
Production of Exotic Nuclei via MNT Reactions Using Gas Cells
The use of multi-nucleon transfer (MNT) reactions to produce neutron-rich nuclei in the heavy region has received an increased attention in the last decade. The feasibility of employing such reactions at the FRS Ion Catcher facility at GSI and the IGISOL facility at JYFL is studied using a combination of theoretical calculations and experiment simulations. The reactions are computed within a Langevin-type model, and the Geant program is used to simulate the transport of the resulting products within the experimental setups of the above-mentioned facilities. The angular distribution of ion release, possible target choices and target-to-beam-dump distances are discussed. peerReviewed
Laser Spectroscopy of Neutron-Rich Tin Isotopes: A Discontinuity in Charge Radii across the N=82 Shell Closure
Physical review letters 122(19), 192502 (2019). doi:10.1103/PhysRevLett.122.192502
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.
From Calcium to Cadmium: Testing the Pairing Functional through Charge Radii Measurements of Cd100−130
Differences in mean-square nuclear charge radii of $^{100--130}\mathrm{Cd}$ are extracted from high-resolution collinear laser spectroscopy of the $5s\text{ }{^{2}S}_{1/2}\ensuremath{\rightarrow}5p\text{ }{^{2}P}_{3/2}$ transition of the ion and from the $5s5p\text{ }{^{3}P}_{2}\ensuremath{\rightarrow}5s6s\text{ }{^{3}S}_{1}$ transition in atomic Cd. The radii show a smooth parabolic behavior on top of a linear trend and a regular odd-even staggering across the almost complete $sdgh$ shell. They serve as a first test for a recently established new Fayans functional and show a remarkably good agreement in the trend as well as in the total nuclear charge radius.
Evidence of octupole-phonons at high spin in 207Pb
A lifetime measurement of the 19/2 state in Pb has been performed using the Recoil Distance Doppler-Shift (RDDS) method. The nuclei of interest were produced in multi-nucleon transfer reactions induced by a Pb beam impinging on a Mo enriched target. The beam-like nuclei were detected and identified in terms of their atomic mass number in the VAMOS++ spectrometer while the prompt γ rays were detected by the AGATA tracking array. The measured large reduced transition probability B(E3,19/2→13/2)=40(8) W.u. is the first indication of the octupole phonon at high spin in Pb. An analysis in terms of a particle-octupole-vibration coupling model indicates that the measured B(E3) value in Pb is compa…
Coulomb Excitation ofCu68,70: First Use of Postaccelerated Isomeric Beams
We report on the first low-energy Coulomb excitation measurements with radioactive Ipi=6- beams of odd-odd nuclei 68,70Cu. The beams were produced at ISOLDE, CERN and were post-accelerated by REX-ISOLDE to 2.83 MeV/nucleon. gamma rays were detected with the MINIBALL spectrometer. The 6- beam was used to study the multiplet of states (3-, 4-, 5-, 6-) arising from the pi2p3/2nu1g9/2 configuration. The 4- state of the multiplet was populated via Coulomb excitation and the B(E2;6--->4-) value was determined in both nuclei. The results obtained illustrate the fragile stability of the Z=28 shell and N=40 subshell closures. A comparison with large-scale shell-model calculations using the 56Ni core…
97/37 Rb 60 : The Cornerstone of the Region of Deformation around A∼100
Excited states of the neutron-rich nuclei 97,99Rb were populated for the first time using the multistep Coulomb excitation of radioactive beams. Comparisons of the results with particle-rotor model calculations provide clear identification for the ground-state rotational band of 97Rb as being built on the πg9/2 [431] 3/2+ Nilsson-model configuration. The ground-state excitation spectra of the Rb isotopes show a marked distinction between single-particle-like structures below N=60 and rotational bands above. The present study defines the limits of the deformed region around A∼100 and indicates that the deformation of 97Rb is essentially the same as that observed well inside the deformed regi…
Cluster-transfer reactions with radioactive beams: A spectroscopic tool for neutron-rich nuclei
An exploratory experiment performed at REX-ISOLDE to investigate cluster-transfer reactions with radioactive beams in inverse kinematics is presented. The aim of the experiment was to test the potential of cluster-transfer reactions at the Coulomb barrier as a mechanism to explore the structure of exotic neutron-rich nuclei. The reactions Li7(Rb98,αxn) and Li7(Rb98,txn) were studied through particle-γ coincidence measurements, and the results are presented in terms of the observed excitation energies and spins. Moreover, the reaction mechanism is qualitatively discussed as a transfer of a clusterlike particle within a distorted-wave Born approximation framework. The results indicate that cl…
Mass measurements of As, Se, and Br nuclei, and their implication on the proton-neutron interaction strength toward the N=Z line
Mass measurements of the $^{69}$As, $^{70,71}$Se and $^{71}$Br isotopes, produced via fragmentation of a $^{124}$Xe primary beam at the FRS at GSI, have been performed with the multiple-reflection time-of-flight mass spectrometer (MR-TOF-MS) of the FRS Ion Catcher with an unprecedented mass resolving power of almost 1,000,000. For the $^{69}$As isotope, this is the first direct mass measurement. A mass uncertainty of 22 keV was achieved with only 10 events. For the $^{70}$Se isotope, a mass uncertainty of 2.6 keV was obtained, corresponding to a relative accuracy of $\delta$m/m = 4.0$\times 10^{-8}$, with less than 500 events. The masses of the $^{71}$Se and $^{71}$Br isotopes were measured…
g factors of $^{31,32,33}$Al: Indication for intruder configurations in the $^{33}$Al ground state
Abstract The g factors of 31,32,33 Al have been measured using the β -nuclear magnetic resonance ( β -NMR) technique on spin-polarized beams produced in the fragmentation of a 36 S (77.5 MeV/u) beam on a 9 Be target. Nearly pure beams of Al ( Z = 13 ) isotopes were selected with the high-resolution fragment separator LISE at GANIL. An asymmetry as high as 6% has been observed in the β -NMR curve for 32 Al implanted in a Si single crystal. The magnetic moment of the N = 20 nucleus 33 Al is obtained for the first time: μ ( Al 33 , I π = 5 / 2 + ) = 4.088 ( 5 ) μ N , while those of 31,32 Al are obtained with improved accuracy: μ ( Al 31 , I π = 5 / 2 + ) = 3.830 ( 5 ) μ N and μ ( Al 32 , I π =…
Spins and electromagnetic moments of Cd101–109
The neutron-deficient cadmium isotopes have been measured by high-resolution laser spectroscopy at CERN-ISOLDE. The electromagnetic moments of $^{101}\mathrm{Cd}$ have been determined for the first time and the quadrupole-moment precision of $^{103}\mathrm{Cd}$ has been vastly improved. The results on the sequence of $5/{2}^{+}$ ground states in $^{101--109}\mathrm{Cd}$ are tentatively discussed in the context of simple structure in complex nuclei as similarities are found with the $11/{2}^{\ensuremath{-}}$ states in the neutron-rich cases. Comparison with shell-model calculations reveals a prominent role of the two holes in the $Z=50$ core.
AGATA-Advanced GAmma Tracking Array
WOS: 000300864200005