Spectroscopy Of Neutron-rich Nuclei Research Articles

EXOGAM at the ILL: the EXILL campaign

Radiative capture reactions on rare targets and prompt spectroscopy of neutron-rich nuclei produced in the neutron-capture induced-fission of 235U and 241Pu have been performed at the Institut Laue-Langevin (ILL). The high efficiency germanium (Ge) EXOGAM array has been used, complemented with Ge detectors from GASP and the ILL. LaBr3 detectors from the FATIMA collaboration have also been coupled to EXOGAM to measure lifetimes of lowlying excited states. The measured characteristics indicate very good performances of the overall setup. Some recent results will be discussed.

The EXILL campaign

A combination of germanium detectors was installed at the PF1B neutron guide of the ILL to perform prompt spectroscopy of neutron-rich nuclei produced in the neutron-capture induced-fission of $^{235}$U and ^${241}$Pu. In addition, La$Br_3$ detectors from the FATIMA Collaboration were installed to complement with the EXOGAM clovers to measure lifetimes of low-lying excited states. The measured characteristics and online spectra indicate very good performances of the overall set-up.

$\gamma $ Spectroscopy of Neutron-rich Nuclei with $A\approx 100$ Produced by Cluster Transfer Reactions at REX-ISOLDE

In this work, we present an exploratory experiment performed at REX-ISOLDE to investigate neutron-rich Sr, Y and Zr nuclei around mass A = 100 by cluster transfer reactions of radioactive 98Rb/98Sr beams on a 7Li target. The goal of the experiment is to test the potential of clustertransfer mechanism to study the low-lying structure of neutron-rich nuclei, performing, as a first case, a -spectroscopy study of the structure in deformed nuclei beyond N = 60 populated, so far, only via β decay and spontaneous fission experiments.

Spectroscopy of neutron rich nuclei using cold neutron induced fission of actinide targets at the ILL: The EXILL campaign

One way to explore exotic nuclei is to study their structure by performing γ-ray spectroscopy. At the ILL, we exploit a high neutron flux reactor to induce the cold fission of actinide targets. In this process, fission products that cannot be accessed using standard spontaneous fission sources are produced with a yield allowing their detailed study using high resolution γ-ray spectroscopy. This is what was pursued at the ILL with the EXILL (for EXOGAM at the ILL) campaign. In the present work, the EXILL setup and performance will be presented.

Decay spectroscopy of neutron-rich nuclei with A ≃ 100

We review structure data obtained by decay spectroscopy of neutron-rich nuclei of mass close to 100. Emphasis is put on the contribution of experiments at IGISOL in the nineties. They confirmed the earlier postulated shape coexistence in the fast shape-transition region between N = 58 (spherical ground states and low collectivity) and N = 60 (strong axial deformation). A detailed spectroscopic study of the A = 99 chain established the upper-Z limit of the N = 56 shell closure region with 99Nb, owing to striking similarities with 97Y. A consequence of the N = 56 closure is that the s1/2 odd-neutron becomes the ground state of the most neutron-rich N = 57 isotones, starting with 99Mo, instead of the degenerated d5/2 and g7/2 subshells familiar in the tin region. Consequences on the change of spin on astrophysical r-process calculations are briefly discussed. Finally, we say a few words about neutron-rich rhodium and palladium isotopes near the neutron midshell where regular and intruder states coexist very close to each other.

Gamma spectroscopy of neutron-rich nuclei with the CLARA-PRISMA setup

The CLARA-PRISMA experimental set-up combines the large acceptance magnetic spectrometer for heavy ions PRISMA with the highly efficient CLARA array of 25 Clover detectors. Selected results on the structure of neutron-rich nuclei, populated in multinucleon transfer and deep-inelastic reactions, are presented here. Some technical developments of the setup are also discussed.

Spectroscopy of neutron-rich nuclei at REX-ISOLDE with MINIBALL

We report on “safe” Coulomb excitation of neutron-rich nuclei. The radioactive nuclei have been produced by ISOLDE at CERN and postaccelerated by the REX-ISOLDE facility. The γ rays emitted by the decay of excited states have been detected by the MINIBALL array. Recent results are presented and compared to theoretical models.

Two-quasiparticle bands in neutron-rich nuclei

The large multi-detector arrays such as EUROBALL and GAMMASPHERE have made possible the study of the spectroscopy of neutron-rich nuclei through the observation of discrete, prompt $\gamma$ -rays emitted following fission. Most of the information obtained has concerned yrast states and collective excitations. In the present work, a search has been made for excited bands based upon two-quasiparticle intrinsic structures. Such bands have been found in several even-even nuclei from 96Sr to 112Pd. Careful analysis of triple-coincidence spectra has been performed in order to determine branching ratios within the bands. These branching ratios are then used to establish the magnetic properties of the intrinsic structure, permitting, in most cases, the determination of which Nilsson orbits (and whether they are neutron or proton states) are contributing to the excitation. Some example results from this search are presented.

The yrast spectroscopy of neutron-rich nuclei produced in deep-inelastic processes

The highly sensitive GASP array at the INFN Legnaro Laboratory was used to study the \(\gamma\)-ray de-excitation of neutron-rich nuclei produced in the deep-inelastic processes which occur when 230 MeV 36S ions interact with a target of 176Yb. Yrast decay schemes were identified in over forty target-like fragments and in over twenty projectile-like fragments. Analysis of the data has resulted in extensions to the yrast decay sequences of the target-like species, 176Hf, 166Er, 172Yb, and 152Sm. New transitions have also been observed in a number of projectile-like species including 34P and 41Cl. Experimental results are compared with the results of shell model calculations.

The structure and spectroscopy of neutron-rich nuclei

Our knowledge of the structure and spectroscopy of neutron-rich nuclei has greatly increased due to two important developments in nuclear physics: the construction of large γ-ray arrays to investigate prompt γ-rays from fission and deep-inelastic reactions; and the availability of radioactive nuclei from fragmentation and spallation reactions. In this review examples will be given of the advances that have been made in our understanding of the properties of neutron-rich nuclei. The examples are necessarily selective, given the limitations of space and time.

High-spin states in neutron-rich nuclei explored with deep-inelastic HI reactions

The use of deep-inelastic heavy-ion reactions for the spectroscopy of neutron-rich nuclei is discussed. Conclusions from the N/Z equilibration process studies are outlined and examples of spectroscopic results obtained for the neutron-rich spdf shell nuclei, N = 82 isotones and nuclei from the 208Pb region are reviewed.

Microscopy of femtoscale structures

Advances in experimental techniques are discussed for the study of long-lived isomers using gammasphere. Spectroscopy of neutron-rich nuclei in the A ∼ 180 region is made possible for the first time via neutron transfer from heavy beams, and long-predicted high-K isomers are observed.

Conference Series 51: Nuclear Spectroscopy of Fission Products

T von Egidy (ed) 1980 Bristol: Institute of Physics x + 334 pp price £29 (IOP members' price £21.75) This volume in The Institute of Physics Conference Series is the product of a workshop on the nuclear spectroscopy of neutron rich nuclei produced in fission and spallation reactions, which was held at ILL, Grenoble. The 25 invited and 10 contributed papers fall into three main categories, namely the techniques used to separate and isolate the product nuclei, general properties of fission products such as delayed neutron spectra, and detailed studies of the properties of the product nuclei.

Spectroscopy of neutron-rich nuclei produced inC14induced reactions onCa48

Mass excess values and energies of excited states were determined for the neutron-rich nuclei $^{46}\mathrm{Ar}$ and $^{48}\mathrm{K}$ and tentatively for $^{51}\mathrm{Ca}$ by use of $^{14}\mathrm{C}$ induced transfer reactions on $^{48}\mathrm{Ca}$.NUCLEAR REACTIONS $^{42}\mathrm{Ca}$($^{14}\mathrm{C}$, $^{16}\mathrm{O}$)$^{40}\mathrm{Ar}$, $^{48}\mathrm{Ca}$($^{14}\mathrm{C}$, $^{16}\mathrm{O}$)$^{46}\mathrm{Ar}$, $^{42}\mathrm{Ca}$($^{14}\mathrm{C}$, $^{14}\mathrm{N}$)$^{42}\mathrm{K}$, $^{48}\mathrm{Ca}$($^{14}\mathrm{C}$, $^{14}\mathrm{N}$)$^{48}\mathrm{K}$, $^{48}\mathrm{Ca}$($^{14}\mathrm{C}$, $^{11}\mathrm{C}$)$^{51}\mathrm{Ca}$; $E=67, 75, \mathrm{and} 78$ MeV; measured mass excess values and excited states in $^{46}\mathrm{Ar}$, $^{48}\mathrm{K}$, $^{51}\mathrm{Ca}$; enriched targets.