The known I^{π}=8_{1}^{+}, E_{x}=2129-keV isomer in the semimagic nucleus ^{130}Cd_{82} was populated in the projectile fission of a ^{238}U beam at the Radioactive Isotope Beam Factory at RIKEN. The high counting statistics of the accumulated data allowed us to determine the excitation energy, E_{x}=2001.2(7)  keV, and half-life, T_{1/2}=57(3)  ns, of the I^{π}=6_{1}^{+} state based on γγ coincidence information. Furthermore, the half-life of the 8_{1}^{+} state, T_{1/2}=224(4)  ns, was remeasured with high precision. The new experimental information, combined with available data for ^{134}Sn and large-scale shell model calculations, allowed us to extract proton and neutron effective charges for ^{132}Sn, a doubly magic nucleus far-off stability. A comparison to analogous information for ^{100}Sn provides first reliable information regarding the isospin dependence of the isoscalar and isovector effective charges in heavy nuclei.

The change of the shell structure in atomic nuclei, so-called “nuclear shell evolution”, occurs due to changes of major configurations through particle-hole excitations inside one nucleus, as well as due to variation of the number of constituent protons or neutrons. We have investigated how the shell evolution affects Gamow-Teller (GT) transitions that dominate the β decay in the region below 132Sn using the newly obtained experimental data on a long-lived isomer in 127Ag. The T1/2=67.5(9) ms isomer has been identified with a spin and parity of (27/2+) at an excitation energy of 1942−20+14 keV, and found to decay via an internal transition of an E3 character, which competes with the dominant β-decay branches towards the high-spin states in 127Cd. The underlying mechanism of a strong GT transition from the 127Ag isomer is discussed in terms of configuration-dependent optimization of the effective single-particle energies in the framework of a shell-model approach.

Newly observed decay schemes of the nuclei Sb-137 and Sb-138 are reported. The neutron-rich Sb isotopes were produced by the in-flight fragmentation of a U-238 primary beam with an energy of 345 MeV/nucleon. Several new excited states of Te-137 with tentatively assigned spin-parities of (5/2(-)), (9/2(-)), and (7/2) have been established which play an important role in the evolution of neutron levels beyond N = 82. The study of the beta decay of Sb-138 led to a considerable extension of the level scheme of Te-138 including the identification of several nonyrast states. The structure of Te-137 and Te-138 is discussed on the basis of large-scale shell-model calculations performed using two different effective interactions.

In a high-energy fragmentation experiment at GSI an I=π(6+) isomer and its γ-decay are identified in 102Sn, the two-neutron neighbour of the doubly-magic 100Sn. Its half-life is measured to be T=1/2367(11) ns. The possible existence of further isomers is discussed in the framework of large-scale shell model (LSSM) calculations including up to five particle-hole excitations of the 100Sn core. From the precise B(E2; 6+→4+) strength and the recently remeasured value for B(E2; 8+→6+) in the two-proton hole neighbour 98Cd effective E2 polarization charges for protons and neutrons were inferred including LSSM corrections within the full N=4 0ħω space. The results are discussed in comparison to predicted and empirically determined effective operators.

We report on new gamma-ray spectroscopy results from beta decays of In-99 and Sn-101. 30 new gamma rays were observed following the beta decay of In-99, and inconsistencies in the literature with respect to the gamma rays following the beta decay of Sn-101 were addressed with two confirmed cases and two new transitions. The experimental gamma-ray energies, intensities, and coincidence relationships are discussed with shell model calculations, where theoretical beta-decay branching ratios from the parent nuclei and gamma-ray cascades of excited states from the daughter nuclei were combined to generate hypothetical beta gamma spectra and beta gamma gamma coincidence matrices. The most intense beta-delayed gamma-ray branches in both Cd-99 and In-101 were well reproduced with this approach, and several gamma rays were assigned to new excited states based on their good agreement with shell model predictions.

Jungclaus, A.; Keatings, J. M.; Simpson, G. S.; Naïdja, H.; Gargano, A.; Nishimura, S.; Doornenbal, P.; Gey, G.; Lorusso, G.; Soderstrom, P.-A.; Sumikama, T.; Taprogge, J.; Xu, Z. Y.; Baba, H.; Browne, F.; Fukuda, N.; Inabe, N.; Isobe, T.; Jung, H. S.; Kameda, D.; Kim, G. D.; Kim, Y.-K.; Kojouharov, I.; Kubo, T.; Kurz, N.; Kwon, Y. K.; Li, Z.; Sakurai, H.; Schaffner, H.; Shimizu, Y.; Suzuki, H.; Takeda, H.; Vajta, Z.; Watanabe, H.; Wu, J.; Yagi, A.; Yoshinaga, K.; Bönig, S.; Daugas, J.-M.; Gernhauser, R.; Ilieva, S.; Kröll, T.; Montaner-Piza, A.; Moschner, K.; Mücher, D.; Nishibata, H.; Odahara, A.; Orlandi, R.; Scheck, M.; Steiger, K.

The decay of five neutron-heavy rhodium isotopes were studied at the Radioactive Isotope Beam Factory (RIBF) Facility at the RIKEN Nishina Center after relativistic fission of 238 U beam on a thick beryllium target. Previously unknown associated gamma-ray decay energies are reported for each nuclide, and through evaluating the intensity of the 2 + → 0 + E2 transition in the even-even palladium daughter nuclei, 120,122,124 Pd, from the beta-tagged gamma-ray spectra an upper or lower limit of beta-delayed neutron emission is deduced for each nuclei. A general, expected trend of increasing P n is observed in the direction of the neutron drip line.

A record number of ^{100}Sn nuclei was detected and new isotopic species toward the proton dripline were discovered at the RIKEN Nishina Center. Decay spectroscopy was performed with the high-efficiency detector arrays WAS3ABi and EURICA. Both the half-life and the β-decay end point energy of ^{100}Sn were measured more precisely than the literature values. The value and the uncertainty of the resulting strength for the pure 0^{+}→1^{+} Gamow-Teller decay was improved to B_{GT}=4.4_{-0.7}^{+0.9}. A discrimination between different model calculations was possible for the first time, and the level scheme of ^{100}In is investigated further.

The study of nuclei in the region around the N = Z doubly-magic nucleus Sn-100 has been of long standing interest for the nuclear structure and nuclear astrophysics. Recently, Park et al. have reported on properties of gamma-decaying isomers and isomeric ratios in the vicinity of Sn-100. That experiment was performed at the Radioactive Ion Beam Factory (RIBF) of the RIKEN Nishina Center in Japan as a part of the EURICA campaign. Neutron-deficient nuclei were produced in a fragmentation reaction of a Xe-124 primary beam on a 9 Be target at an energy of 345 MeV/A. Secondary ions were separated and identified in the BigRIPS fragment separator and implanted in the silicon detector array WAS3ABi. The data presented here were obtained in another experiment performed at the RIBF using the same reaction but slightly different separator settings. New results of ratios of isomeric population and half-lives of gamma-decaying isomers populated in the experiment are presented.

A gamma -decaying isomeric state (tau(1/2) = 197(-17)(+19) ns) has been identified in Cd-96, which is one alpha particle away from the last known bound N = Z nucleus, Sn-100. Comparison of the results with shell-model calculations has allowed a tentative experimental level scheme to be deduced and the isomer to be interpreted as a medium-spin negative-parity spin trap based on the coupling of isoscalar (T = 0) and isovector (T = 1) neutron-proton pairs. The data also suggest evidence for the population of a 9(+) T = 1 state, which is predicted by shell-model calculations to be yrast. Such a low-lying T = 1 state, which is unknown in lighter mass even-even self-conjugate nuclei, can also be interpreted in terms of the coupling of T = 0 and T = 1 neutron-proton pairs.

A systematic study was performed of microsecond gamma-decaying isomers around Sn-100 produced in a fragmentation reaction of a Xe-124 beam at 345 MeV/u at the Radioactive Ion Beam Factory of the RIKEN Nishina Center in Saitama, Japan. Half-lives of isomeric states in that region were remeasured allowing us to improve the currently available experimental information. Reduced transition probabilities were deduced and compared to shell-model calculations in various model spaces. The recently reported low-energy transitions in Rh-92 and Ag-96 were remeasured with improved precision. Additionally, experimental information on isomeric ratios, including five new ones, were extracted and compared to a previous experimental study and the sharp cutoff model of fragmentation reaction.

The neutron-rich isotopes of palladium have attracted considerable interest in terms of the evolution of the N=82 neutron shell closure and its influence on the r-process nucleosynthesis. In this Letter, we present the first spectroscopic information on the excited states in 125Pd79 and 127Pd81 studied using the EURICA γ-ray spectrometer, following production via in-flight fission of a high-intensity 238U beam at the RIBF facility. New isomeric states with half-lives of 144(4) ns and 39(6) μs have been assigned spins and parities of (23/2+) and (19/2+) in 125Pd and 127Pd, respectively. The observed level properties are compared to a shell-model calculation, suggesting the competition between proton excitations and neutron excitations in the proton-hole and neutron-hole systems in the vicinity of the doubly magic nucleus 132Sn.

A decay spectroscopy experiment on proton-rich nuclei in the vicinity of the doubly magic $^{100}\mathrm{Sn}$ was carried out at RIKEN Nishina Center. More than 20 nuclei with $43\ensuremath{\le}Z\ensuremath{\le}50$ and $N\ensuremath{\le}51$, produced by fragmentation reactions were investigated via analyses of $\ensuremath{\beta}$-decay, $\ensuremath{\beta}p$-decay, and subsequent $\ensuremath{\gamma}$-ray data. Owing to higher statistics, the precision on the half-lives of many of the ground states and isomers was improved. $\ensuremath{\beta}$-decay endpoint energies of 11 states in 8 nuclei were measured for the first time, and the corresponding ${Q}_{\text{EC}}$ and excitation energies were generally consistent with various mass models. Many $\ensuremath{\beta}$-delayed proton emission branching ratios were measured either for the first time or with higher precision compared to literature values, and some of them differed by more than $2\ensuremath{\sigma}$. Many of the large discrepancies were associated with nuclei with long-lived isomeric states, highlighting large systematic uncertainties involved in these measurements. Twenty-five new $\ensuremath{\gamma}$ rays were observed, and ten new states are proposed with unambiguous excitation energies, spins, and parities. Most of the energies of the excited states were consistent within 300 keV or 20%, whichever was greater, compared to shell model predictions in the proton/neutron $({p}_{1/2},{g}_{9/2})$ model space assuming a $^{76}\mathrm{Sr}$ core. A signature of a new $(1/{2}^{\ensuremath{-}})$ isomer in $^{97}\mathrm{Cd}$ with ${T}_{1/2}=0.73(7)$ s was found, in good agreement with shell model predictions.

Gottardo, A.; Valiente-Dobón, J. J.; Benzoni, G.; Morales, A. I.; Gadea, A.; Lunardi, S.; Boutachkov, P.; Bruce, A. M.; Górska, M.; Grebosz, J.; Pietri, S.; Podolyák, Zs; Pfützner, M.; Regan, P. H.; Rudolph, D.; Weick, H.; Alcántara Núñez, J.; Algora, A.; Al-Dahan, N.; De Angelis, G.; Ayyad, Y.; Alkhomashi, N.; Allegro, P. R.P.; Bazzacco, D.; Benlliure, J.; Bowry, M.; Bracco, A.; Bunce, M.; Camera, F.; Casarejos, E.; Cortes, M. L.; Crespi, F. C.L.; Corsi, A.; Denis Bacelar, A. M.; Deo, A. Y.; Domingo-Pardo, C.; Doncel, M.; Dombradi, Zs; Engert, T.; Eppinger, K.; Farrelly, G. F.; Farinon, F.; Geissel, H.; Gerl, J.; Goel, N.; Gregor, E.; Habermann, T.; Hoischen, R.; Janik, R.; Klupp, S.

The β-delayed γ-ray spectroscopy of neutron-rich ^{123,125}Ag isotopes is investigated at the Radioactive Isotope Beam Factory of RIKEN, and the long-predicted 1/2^{-} β-emitting isomers in ^{123,125}Ag are identified for the first time. With the new experimental results, the systematic trend of energy spacing between the lowest 9/2^{+} and 1/2^{-} levels is extended in Ag isotopes up to N=78, providing a clear signal for the reduction of the Z=40 subshell gap in Ag towards N=82. Shell-model calculations with the state-of-the-art V_{MU} plus M3Y spin-orbit interaction give a satisfactory description of the low-lying states in ^{123,125}Ag. The tensor force is found to play a crucial role in the evolution of the size of the Z=40 subshell gap. The observed inversion of the single-particle levels around ^{123}Ag can be well interpreted in terms of the monopole shift of the π1g_{9/2} orbitals mainly caused by the increasing occupation of ν1h_{11/2} orbitals.

The neutron-rich isotopes Tl-211,Tl-213, beyond the N = 126 shell closure, have been studied for the first time in isomer gamma-ray decay, exploiting the fragmentation of a primary uranium beam at the Fragment Separator-Rare Isotopes Investigation at GSI setup. The observed isomeric states in Tl-211,Tl-213 show a deviation from the seniority-like scheme of Tl-209. The possible interpretation of the data is discussed on the basis of energy-level systematics and shell-model calculations.

A decay spectroscopy experiment on proton-rich nuclei in the vicinity of the doubly magic Sn-100 was carried out at RIKEN Nishina Center. More than 20 nuclei with 43 <= Z <= 50 and N <= 51, produced by fragmentation reactions were investigated via analyses of beta-decay, beta p-decay, and subsequent gamma-ray data. Owing to higher statistics, the precision on the half-lives of many of the ground states and isomers was improved. beta-decay endpoint energies of 11 states in 8 nuclei were measured for the first time, and the corresponding Q(EC) and excitation energies were generally consistent with various mass models. Many beta-delayed proton emission branching ratios were measured either for the first time or with higher precision compared to literature values, and some of them differed by more than 2 sigma. Many of the large discrepancies were associated with nuclei with long-lived isomeric states, highlighting large systematic uncertainties involved in these measurements. Twenty-five new gamma rays were observed, and ten new states are proposed with unambiguous excitation energies, spins, and parities. Most of the energies of the excited states were consistent within 300 keV or 20%, whichever was greater, compared to shell model predictions in the proton/neutron (P-1/2, g(9/2)) model space assuming a Sr-76 core. A signature of a new (1/2(-)) isomer in Cd-97 with T-1/2 = 0.73(7) s was found, in good agreement with shell model predictions.

We report on new or more precise half-lives, beta-decay endpoint energies, and beta-delayed proton emission branching ratios of(91) Pd, Cd-95,In-97, and Sn-99. The measured values are consistent with known mirror transitions in lighter T-z = -1/2 nuclei, shell-model calculations, and various mass models. In addition to the beta -decaying (9/2(+)) ground state, circumstantial evidence for a short-lived, proton-emitting isomer with spin (1 /2(-)) was found in(97)In. Based on the experimental data, a semiempirical theory on proton emission, and shell-model calculations, the proton separation energy of the In-97 ground state was determined to be -0.10 +/- 0.19 MeV. The existence of the short-lived, proton-unstable (1 /2(-)) isomer in In-97 establishes Cd-9S as an rp-process waiting point.