Coulomb excitation of the |Tz|=1/2, A=23 mirror pair

Background: Electric-quadrupole (E2) strengths relate to the underlying quadrupole deformation of a nucleus and present a challenge for many nuclear theories. Mirror nuclei in the vicinity of the line of N=Z represent a convenient laboratory for testing deficiencies in such models, making use of the isospin symmetry of the systems. Purpose: Uncertainties associated with literature E2 strengths in 23Mg are some of the largest in Tz=∣∣12∣∣ nuclei in the sd shell. The purpose of the present paper is to improve the precision with which these values are known, to enable better comparison with theoretical models. Methods: Coulomb-excitation measurements of 23Mg and 23Na were performed at the TRIU…

Decay studies in the A∼225 Po-Fr region from the DESPEC campaign at GSI in 2021

The HISPEC-DESPEC collaboration aims at investigating the struc-ture of exotic nuclei formed in fragmentation reactions with decay spectroscopymeasurements, as part of the FAIR Phase-0 campaign at GSI. This paper reportson first results of an experiment performed in spring 2021, with a focus on beta-decaystudies in the Po-Fr nuclei in the 220 < A <230 island of octupole deformationexploiting the DESPEC setup. Ion-beta correlations and fast-timing techniques arebeing employed, giving an insight into this difficult-to-reach region. peerReviewed

Isospin symmetry in $B(E2)$ values: Coulomb excitation study of ${}^{21}$Mg

The $T_z$~=~$-\frac{3}{2}$ nucleus ${}^{21}$Mg has been studied by Coulomb excitation on ${}^{196}$Pt and ${}^{110}$Pd targets. A 205.6(1)-keV $\gamma$-ray transition resulting from the Coulomb excitation of the $\frac{5}{2}^+$ ground state to the first excited $\frac{1}{2}^+$ state in ${}^{21}$Mg was observed for the first time. Coulomb excitation cross-section measurements with both targets and a measurement of the half-life of the $\frac{1}{2}^+$ state yield an adopted value of $B(E2;\frac{5}{2}^+\rightarrow\frac{1}{2}^+)$~=~13.3(4)~W.u. A new excited state at 1672(1)~keV with tentative $\frac{9}{2}^+$ assignment was also identified in ${}^{21}$Mg. This work demonstrates large difference…

Experimental investigation of the 0⁺₂ band in ¹⁵⁴Sm as a β-vibrational band

Determination of absolute internal conversion coefficients using the SAGE spectrometer

A non-reference based method to determine internal conversion coefficients using the SAGE spectrometer is carried out for transitions in the nuclei of 154Sm, 152Sm and 166Yb. The Normalised-Peak-to-Gamma method is in general an efficient tool to extract internal conversion coefficients. However, in many cases the required well-known reference transitions are not available. The data analysis steps required to determine absolute internal conversion coefficients with the SAGE spectrometer are presented. In addition, several background suppression methods are introduced and an example of how ancillary detectors can be used to select specific reaction products is given. The results obtained for …

Coulomb excitation of the $\left|T_z\right|=\frac{1}{2}$, $A=23$ mirror pair

Background: Electric-quadrupole ($E2$) strengths relate to the underlying quadrupole deformation of a nucleus and present a challenge for many nuclear theories. Mirror nuclei in the vicinity of the line of $N=Z$ represent a convenient laboratory for testing deficiencies in such models, making use of the isospin-symmetry of the systems. Purpose: Uncertainties associated with literature $E2$ strengths in \textsuperscript{23}Mg are some of the largest in $T_z=\left|\frac{1}{2}\right|$ nuclei in the $sd$-shell. The purpose of the present work is to improve the precision with which these values are known, to enable better comparison with theoretical models. Methods: Coulomb-excitation measuremen…

An innovative Superconducting Recoil Separator for HIE-ISOLDE

International audience; The ISOLDE Scientific Infrastructure at CERN offers a unique range of post-accelerated radioactive beams. The scientific program can be improved with the “Isolde Superconducting Recoil Separator” (ISRS), an innovative spectrometer able to deliver unprecedented (A, Z) resolution. In this paper we present an overview of the physics and ongoing technical developments.

Improved measurement of the 02+→01+ E0 transition strength for 72Se using the SPICE spectrometer

The selenium isotopes lie at the heart of a tumultuous region of the nuclear chart where shape coexistence effects grapple with neutron-proton pairing correlations, triaxiality, and the impending proton drip line. In this work, a study of 72Se by internal conversion electron and γ-ray spectroscopy was undertaken with the SPICE and TIGRESS arrays. New measurements of the branching ratio and lifetime of the 02+ state were performed, yielding a determination of ρ2(E0;02+→01+)=29(3) milliunits. Two-state mixing calculations were performed that highlighted the importance of interpretation of such E0 strength values in the context of shape coexistence. peerReviewed

Testing microscopically derived descriptions of nuclear collectivity: Coulomb excitation of Mg

Many-body nuclear theory utilizing microscopic or chiral potentials has developed to the point that collectivity might be studied within a microscopic or ab initio framework without the use of effective charges; for example with the proper evolution of the E2 operator, or alternatively, through the use of an appropriate and manageable subset of particle–hole excitations. We present a precise determination of E2 strength in 22Mg and its mirror 22Ne by Coulomb excitation, allowing for rigorous comparisons with theory. No-core symplectic shell-model calculations were performed and agree with the new B(E2) values while in-medium similarity-renormalization-group calculations consistently underpr…