Mirror energy differences above the 0f7/2 shell: First γ-ray spectroscopy of the Tz = −2 nucleus 56Zn

Excited states in 56Zn were populated following one-neutron removal from a 57Zn beam impinging on a Be target at intermediate energies in an experiment conducted at the Radioactive Isotope Beam Factory at RIKEN. Three γ rays were observed and tentatively assigned to the 6+→4+→2+→0+ yrast sequence. This turns 56Zn into the heaviest Tz=−2 nucleus in which excited states are known. The excitation-energy differences between these levels and the isobaric analogue states in the Tz=+2 mirror partner, 56Fe, are compared with large-scale shell-model calculations considering the full pf valence space and various isospin-breaking contributions. This comparison, together with an analysis of the mirror energy differences in the A=58, Tz=±1 pair 58Zn and 58Ni, provides valuable information with respect to the size of the monopole radial and the isovector multipole isospin-breaking terms in the region above doubly-magic 56Ni

Spectroscopy of the T = 2 mirror nuclei 48Fe/48Ti using mirrored knockout reactions

A sequence of excited states has been established for the first time in the proton-rich nucleus 48Fe (Z=26, N=22). The technique of mirrored (i.e. analogue) one-nucleon knockout reactions was applied, in which the Tz= ±2 mirror pair, 48Fe/48Ti were populated via one-neutron/one-proton knockout from the secondary beams 49Fe/49V, respectively. The analogue properties of the reactions were used to help establish the new level scheme of 48Fe. The inclusive and exclusive cross sections were determined for the populated states. Large differences between the cross sections for the two mirrored reactions were observed and have been interpreted in terms of different degrees of binding of the mirror nuclei and in the context of the recent observations of suppression of spectroscopic strength as a function of nuclear binding, for knockout reactions on light solid targets. Mirror energy differences (MED) have been determined between the analogue T=2 states and compared with the shell model predictions. MED for this mirror pair, due to their location in the shell, are especially sensitive to excitations out of the f7/2 shell, and present a stringent test of the shell-model prescription

Mirror energy differences above the 0f7/2 shell: First γ-ray spectroscopy of the Tz = −2 nucleus 56Zn

Excited states in 56Zn were populated following one-neutron removal from a 57Zn beam impinging on a Be target at intermediate energies in an experiment conducted at the Radioactive Isotope Beam Factory at RIKEN. Three γ rays were observed and tentatively assigned to the 6+→4+→2+→0+ yrast sequence. This turns 56Zn into the heaviest Tz=−2 nucleus in which excited states are known. The excitation-energy differences between these levels and the isobaric analogue states in the Tz=+2 mirror partner, 56Fe, are compared with large-scale shell-model calculations considering the full pf valence space and various isospin-breaking contributions. This comparison, together with an analysis of the mirror energy differences in the A=58, Tz=±1 pair 58Zn and 58Ni, provides valuable information with respect to the size of the monopole radial and the isovector multipole isospin-breaking terms in the region above doubly-magic 56Ni

Analog B(M1) strengths in the Tz=± 32 mirror nuclei Mn 47 and Ti 47

The lifetimes of the first excited 72- states in the Tz=±32 mirror nuclei Mn47 and Ti47 have been extracted utilizing the γ-ray line shape method, giving τ=687(36) ps and τ=331(15) ps respectively. Since these transitions are essentially pure M1 transitions, these results allow for a high-precision comparison of analog M1 strengths in mirror nuclei. The two analog B(M1)s are observed to be identical to a precision of about 10%. The expected dependence of the transition matrix element with Tz has been used to extract the separate isoscalar and isovector components of the transition strength, and the results are discussed in the context of predictions, based on the isospin formalism, regarding analog B(M1) strengths

Spectroscopy of the T= 32 A=47 and A=45 mirror nuclei via one- and two-nucleon knockout reactions

© 2022 authors. Published by the American Physical Society.Level schemes of the proton-rich nuclei, Mn47 (Z=25,N=22) and Cr45 (Z=24,N=21), have been established for the first time. The technique of mirrored one- and two-nucleon knockout reactions was applied to the secondary beams of V48/Mn48 and V47/Cr47 to populate states in Ti47/Mn47 and Sc45/Cr45, respectively. Mirror energy differences (MED) have been studied between the mirrored T=32 states for both mirror pairs and interpreted using both a shell-model approach and a density-functional-theory approach using the no-core configuration-interaction method. MED in this mass region provide a stringent test of the model prescriptions since both fp- and sd-shell orbitals are active and, in Cr45, spherical and well-deformed structures coexist near the ground state. The inclusive and exclusive one-nucleon removal cross sections have been determined for the populated states in Ti47/Mn47 and compared with results from reaction-model calculations.11Nsciescopu

Spectroscopy of the T = 3 2 A = 47 and A = 45 mirror nuclei via one- and two- nucleon knockout reactions

Level schemes of the proton-rich nuclei, 47 Mn (Z = 25, N = 22) and 45 Cr (Z = 24, N = 21), have been established for the first time. The technique of mirrored one-and two-nucleon knockout reactions was applied to the secondary beams of 48 V/ 48 Mn and 47 V/ 47 Cr to populate states in 47 Ti/ 47 Mn and 45 Sc/ 45 Cr, respectively. Mirror energy differences (MED) have been studied between the mirrored T = 3 2 states for both mirror pairs, and interpreted using both a shell-model approach and a density-functional approach using the No-Core Configuration-Interaction (DFT-NCCI) method. MED in this mass region provide a stringent test of the model prescriptions since both fp-and sd-shell orbitals are active and, in 45 Cr, spherical and well-deformed structures co-exist near the ground-state. The inclusive and exclusive one-nucleon removal cross sections have been determined for the populated states in 47 Ti/ 47 Mn and compared with results from reaction-model calculations

Isospin symmetry in the T=1,A=62T = 1, A = 62 triplet

International audienceExcited states in the $T_z = 0, -1$ nuclei $^{62}$Ga and $^{62}$Ge were populated in direct reactions of relativistic radioactive ion beams at the RIBF. Coincident \grays were measured with the DALI2$^+$ array and uniquely assigned to the $A=62$ isobars. In addition, $^{62}$Ge was also studied independently at JYFL-ACCLAB using the ${}^{24}$Mg(${}^{40}$Ca,$2n$)${}^{62}$Ge fusion-evaporation reaction. The first excited $T=1, J^\pi =2^+$ states in $^{62}$Ga and $^{62}$Ge were identified at $979(1)$ and $965(1)$~keV, respectively, resolving discrepant interpretations in the literature. States beyond the first $2^+$ state in $^{62}$Ge were also identified for the first time in the present work. The results are compared with shell-model calculations in the $fp$ model space. Mirror and triplet energy differences are analyzed in terms of individual charge-symmetry and charge-independence breaking contributions. The MED results confirm the shrinkage of the $p$-orbits' radii when they are occupied by at least one nucleon on average