P. Adrich

Application of the time-of-flight technique for lifetime measurements with relativistic beams of heavy nuclei

Abstract A novel method for picosecond lifetime measurements of excited γ -ray emitting nuclear states has been developed for fast beams from fragmentation reactions. A test measurement was carried out with a beam of 124Xe at an energy of ∼ 55 MeV / u . The beam ions were Coulomb excited to the 2 1 + state on a movable target. Excited nuclei emerged from the target and decayed in flight after a distance related to the lifetime. A stationary degrader positioned downstream with respect to the target was used to further reduce the velocity of the excited nuclei. As a consequence, the γ -ray decays from the 2 1 + excited state that occurred before or after traversing the degrader were measured at a different Doppler shift. The γ -ray spectra were analyzed from the forward ring of the Segmented Germanium Array; this ring positioned at 37 ∘ simultaneously provides the largest sensitivity to changes in β and the best-energy resolution. The ratio of intensities in the peaks at different Doppler shifts gives information about the lifetime if the velocity β is measured. The results and range of the application of the method are discussed.

In-beam gamma-ray spectroscopy of very neutron-rich nuclei: excited states in 46S and 48Ar.

We report on the first in-beam gamma-ray spectroscopy study of the very neutron-rich nucleus 46S. The N=30 isotones 46S and 48Ar were produced in a novel way in two steps that both necessarily involve nucleon exchange and neutron pickup reactions 9Be(48Ca,48K)X followed by 9Be(48K,48Ar+gamma)X at 85.7 MeV/u midtarget energy and 9Be(48Ca,46Cl)X followed by 9Be(46Cl,46S+gamma)X at 87.0 MeV/u midtarget energy, respectively. The results are compared to large-scale shell-model calculations in the sd-pf shell using the SDPF-NR effective interaction and Z-dependent modifications.

Isobaric Analogue States Studied in Mirrored Fragmentation and Knockout Reactions

A Gamma-ray spectroscopic study of excited states of isobaric multiplets has been performed in recent years, with a view to gaining a quantitative understanding of energy differences between excited states in terms of a range of Coulomb and other isospin breaking phenomena. Recently, the experimental programme has been augmented by a study of isobaric analogue states of mirror nuclei populated in mirrored fragmentation reactions. In this presentation, recent results on the

Plunger lifetime measurements after Coulomb excitation at intermediate beam energies

T =\frac{3}{2}

In-beam gamma-ray spectroscopy and inclusive two-proton knockout cross section measurements at N approximate to 40

analogue states in the

Inverse-kinematics one-proton pickup with intermediate-energy beams: The {sup 9}Be ({sup 20}Ne,{sup 21}Na+{gamma})X reaction

T_z =\pm \frac{3}{2}

Reduction of spectroscopic strength: Weakly-bound and strongly-bound single-particle states studied using one-nucleon knockout reactions

mirror pair 53Ni/53Mn will be summarised. In this work, further strong evidence is found for the need to include an anomalous isospin-breaking two-body matrix element for angular-momentum couplings of J = 2, in addition the expected Coulomb contribution, in order to account for the experimental data.

Collectivity of neutron-rich palladium isotopes and the valence proton symmetry

Absolute transition probabilities of the first 2{sup +} state in {sup 110,114}Pd were remeasured using the recoil distance Doppler shift technique following projectile Coulomb excitation at intermediate beam energies for the first time. The {sup 110}Pd experiment served to check the novel technique as well as the method used for the data analysis which is based on the examination of {gamma}-ray lineshapes. Whereas the measured B(E2) value for {sup 110}Pd agrees very well with the literature, the value obtained for {sup 114}Pd differs considerably. The data is also used to test a novel concept, called the valence proton symmetry, which allows one to extrapolate nuclear properties to very neutron rich nuclei.

CAESAR—A high-efficiency CsI(Na) scintillator array for in-beam γ‐ray spectroscopy with fast rare-isotope beams

In-beam {gamma}-ray spectroscopy of {sup 66,68}Fe following intermediate-energy one- and two-proton knockout from cobalt and nickel secondary beams has been performed at the National Superconducting Cyclotron Laboratory. New transitions have been observed in {sup 66}Fe and {sup 68}Fe. This is the first observation of {gamma}-ray transitions in {sup 68}Fe. In addition, {sup 64}Cr was produced using the {sup 9}Be({sup 66}Fe,{sup 64}Cr)X two-proton knockout reaction. An unexpectedly low inclusive cross section is observed for this reaction, an order of magnitude smaller than for the {sup 9}Be({sup 68}Ni,{sup 66}Fe)X reaction. This observation is discussed in terms of a significant structural difference between {sup 66}Fe and {sup 64}Cr and considerable admixtures of {nu}(pf){sup n-2}(g{sub 9/2}){sup +2} configurations in the ground and excited states of {sup 64}Cr at N=40.

Shape and structure of N=Z 64Ge: electromagnetic transition rates from the application of the recoil distance method to a knockout reaction.

The possibility of studying particle-like states near the Fermi surfaces of exotic nuclei by using measurements of heavy-ion-induced single-nucleon pickup reactions with in-flight separated rare-isotope beams is discussed. The analysis of an exploratory data set for the intermediate-energy {sup 9}Be({sup 20}Ne,{sup 21}Na)X proton pickup reaction measured using a {sup 20}Ne beam at 63 MeV per nucleon is reported. The data are compared with expectations based on model calculations of the transfer reaction cross sections and the {sup 21}Na residue spectroscopy prediction by the sd-shell model. The measured cross sections are broadly consistent with these expectations.