The -decay fine structure of ^179 Hg and ^177 Au was studied by means of decay spectroscopy. Two experiments were performed at the Accelerator Laboratory of the University of Jyväskylä (JYFL), Finland, utilizing the recoil separator RITU and a digital data acquisition system. The heavy-ion induced fusion-evaporation reactions ^82_36 Kr + ^100_44 Ru and ^88_38 Kr + ^92_42 Mo were used to produce the ^179 Hg and ^177 Au nuclei, respectively. Studying the evaporation residues (ER, recoils)- α _1 - α _2 correlations and - γ coincidences, a new decay with E _α = 6156(10) keV was observed from ^179 Hg. This decay populates the (9/2 ^- ) excited state at an excitation energy of 131.3(5) keV in ^175 Pt. The internal conversion coefficient for the 131.3(5) keV transition de-exciting this state was measured for the first time. Regarding the ^177 Au nucleus, a new decay with E _α = 5998(9) keV was observed to populate the 156.1(6) keV excited state in ^173 Ir. Two de-excitation paths were observed from this excited state. Moreover, a new 215.7(13) keV transition was observed to depopulate the 424.4(13) keV excited state in ^173 Ir. Properties of the ^179 Hg and ^177 Au decays were examined in a framework of reduced widths and hindrance factors. For clarity and simplicity, the spin and parity assignments (e.g. J^π ) are presented without brackets throughout the text.

The complex low-spin structure of the proton-rich 114 53I61 nucleus has been investigated with the JUROGAM 3 germanium array coupled with the MARA mass separator using the 58 Ni( 64 Zn , alpha 3pn) fusion-evaporation reaction. The depopulation of the previously known high-spin bands to low-spin states is firmly established, fixing the excitation energies, spins and parities of the states. The present results combined with fragmentary communications and results published from the decay of separated mass-114 beams measured long time ago at ORNL and GSI, led to the conclusion that the previously known 6 s, 266 keV, I = (7) isomer has to be repositioned at 134 keV and its spin-parity changed to 4+. Three new isomers are identified from intensity imbalance of the populating and depopulating transitions, one at 204 keV with I = 6+ and a half-life longer than several nanoseconds, and two at 635 and 966 keV with I = 5- and I = 7-, respectively, with half-lives of a few nanoseconds. The spins of one high-spin band are changed from odd to even and a new interpretation of the two resulting bands with even spins is proposed based on cranked Nilsson-Strutinsky calculations. From the comparison of the observed low-spin states with shell-model calculations it is suggested that the states of the ground-state cascade are oblate, while the other positive-parity states and the high-spin negative-parity bands are prolate.

High-spin states of the odd-odd Pr-136 nucleus have been investigated using the Mo-100(Ar-40, 1p3n) reaction with the JUROGAM II gamma-ray spectrometer. Many new transitions and levels were identified in addition to the confirmation of most previously known transitions and levels. The high statistics of the present data set allowed the multipolarity assignments for many transitions to be established, which were previously assigned tentatively. Possible configuration assignments for the bands above the I-pi = 6(+) isomer are analyzed within the tilted axis cranking covariant density functional theory framework, and the experimental energy spectra and ratios of reduced transition probabilities are reproduced fairly well. A complete picture of the band structure of this nucleus is established. In particular, the effect of the neutron h(9/2) and f(7/2) intruder orbitals involved in the configurations of the decoupled bands is discussed in detail.

The very neutron-deficient strongly deformed 117Cs nucleus has been studied using the 58Ni(64Zn, 1 alpha 1p) reaction and JUROGAM 3 gamma -ray detector array coupled to the MARA recoil-mass separator. Three previously known and three newly identified rotational bands were observed up to very high spin and excitation energy. All bands are firmly assigned to 117Cs based on measured mass spectra and interconnecting transitions. The ground-state spin and parity are suggested based on the systematics of low-lying states in odd-even cesium nuclei. The systematics of bandheads in cesium nuclei reveal maximum collectivity and deformation is reached for neutron numbers 64-66, corresponding to the middle of the N = 50-82 magic shell. The rotational frequencies of the first and second crossings in the different bands are similar to those observed in the corresponding bands in the neighboring 119Cs nucleus, suggesting similar deformations of the two nuclei, but enhanced softness in 117Cs. Particle number conserving cranked shell model calculations describe the observed band structures well.

Excited states in the neutron-deficient nuclide Hf155 have been investigated in experiments performed at the Accelerator Laboratory of the University of Jyväskylä. The Hf155 nuclei were produced in fusion-evaporation reactions induced by beams of 295 and 315 MeV Ni58 ions bombarding an isotopically enriched Pd102 target and separated using the recoil mass separator MARA. An isomeric state having a half-life of 510(30) ns was discovered and is interpreted as a seniority υ=3, (πh11/22⊗νf7/2)27/2− configuration. The γ-ray transitions emitted in the deexcitation of the isomeric state to the ground state were identified and a level scheme was constructed, from which the excitation energy of the isomer was determined to be 2581.5(10) keV. A B(E2) value of 0.45(3) W.u. was deduced for the 105.4 keV transition depopulating the isomeric state. The deduced level scheme and B(E2) value are compared with systematics and shell-model calculations. Published by the American Physical Society 2024

Excited states have been observed for the first time in the very neutron-deficient odd-odd nucleus 57120La63. The observed γ rays have been assigned based on coincidences with lanthanum X rays measured with the JUROGAM 3 array and with A=120 fusion-evaporation residues measured with the MARA separator. The observed γ rays form a rotational band which decays to the ground state via a cascade of four low-energy transitions. Based on the systematic comparisons with the heavier odd-odd La isotopes we assign spin-parity 4+ to the ground state and a πh11/2⊗νh11/2 configuration to the rotational band. The nuclear shape has been investigated by the cranked Nilsson-Strutinsky model. Two quasiparticle plus triaxial rotor model calculations including the np interaction nicely reproduce the spin of the inversion between the even- and odd-spin cascades of E2 transitions, giving credit to the np interaction as an important parameter responsible for the mechanism inducing the inversion. The position of the Fermi levels, in particular for neutrons, also has a strong impact on the observed inversion in the chain of lanthanum nuclei.

The changes in mean-squared charge radii of neutron-deficient gold nuclei have been determined using the in-source, resonance-ionization laser spectroscopy technique, at the ISOLDE facility (CERN). From these new data, nuclear deformations are inferred, revealing a competition between deformed and spherical configurations. The isotopes ^{180,181,182}Au are observed to possess well-deformed ground states and, when moving to lighter masses, a sudden transition to near-spherical shapes is seen in the extremely neutron-deficient nuclides, ^{176,177,179}Au. A case of shape coexistence and shape staggering is identified in ^{178}Au which has a ground and isomeric state with different deformations. These new data reveal a pattern in ground-state deformation unique to the gold isotopes, whereby, when moving from the heavy to light masses, a plateau of well-deformed isotopes exists around the neutron midshell, flanked by near-spherical shapes in the heavier and lighter isotopes-a trend hitherto unseen elsewhere in the nuclear chart. The experimental charge radii are compared to those from Hartree-Fock-Bogoliubov calculations using the D1M Gogny interaction and configuration mixing between states of different deformation. The calculations are constrained by the known spins, parities, and magnetic moments of the ground states in gold nuclei and show a good agreement with the experimental results.

Three three-quasiparticle isomers, one at an excitation energy of 2.3 MeV with T1/2 = 0.48(4) & mu;s, and two shorter-lived with unknown half-lives at slightly lower energies have been identified in 129Nd using the MARA + JUROGAM 3 setup and the recoil tagging technique. All three isomers present decay patterns characteristic of high -K isomers. The known 6.7 s ⠂-decaying isomer previously assigned to the 5/2+ level is now assigned to the new 7/2- ground state. A new low-spin 5/2+ isomeric state with a half-life of a few tens of nanoseconds has been identified, while a previously known 2.6 s ⠂-decay activity was assigned to the band head of the ⠃1/2+[411] band. The transitions depopulating the high -K isomers to low-lying states also establish the relative energies of three low-lying one-quasiparticle bands, leading to a new spin-parity assignment of 7/2- to the ground state of 129Nd. The partial half-lives of the depopulating transitions suggest spin-parities 21/2+, 19/2+, and 17/2+ for the three high -K isomers. The properties of the band built on the 21/2+ isomeric state suggest a one neutron-two proton configuration. Based on the results of extensive calculations with different models, we also assign one neutron-two proton configurations to the 19/2+ and 17/2+ isomeric states. The assigned configurations of the 17/2+ and 21/2+ isomeric states involve the ⠄9/2+[404] orbital, which is identified in three-quasiparticle bands of proton-rich A ti 130 nuclei.

The level structure of 158Er has been studied using the Gammasphere spectrometer via the 114Cd(48Ca, 4n) reaction at 215 MeV with both thin (self-supporting) and thick (backed) targets. The level scheme has been con-siderably extended with more than 200 new transitions and six new rotational structures, including two strongly coupled high -K bands. Configuration assignments for the new structures are based on their observed alignments, B(M1)/B(E2) ratios of reduced transition probabilities, excitation energies, and comparisons with neighboring nuclei and theoretical calculations. With increasing angular momentum, this nucleus exhibits Coriolis-induced alignments of both neutrons and protons before it then undergoes a rotation-induced transition from near-prolate collective rotation to a noncollective oblate configuration. This transition occurs via the mechanism of band termination around spin 45 h over bar in three rotational structures. Two distinct lifetime branches, consistent with the crossing of a collective "fast" rotational structure by an energetically favored "slow" terminating sequence, are confirmed for the positive-parity states, and similar behavior is established in the negative-parity states. Weak-intensity, high-energy transitions are observed to feed into the terminating states. At the highest spins,

Two triaxial states of the proton-decaying nucleus 147Tm were studied via a comparison of experimental data to results obtained through nonadiabatic quasiparticle calculations. The experimental data were collected in a recoil-decay tagging study using the vacuum-mode recoil separator MARA coupled with the JUROGAM3 & gamma;-ray spectrometer. The previously proposed level scheme above the triaxial 11/2- (& pi;h11/2) ground state was confirmed, and the level structure was expanded to cover the states above the weakly populated proton-emitting 5/2+ (& pi;d5/2) isomeric state. It was found that the isomeric state is also triaxial, and possibly more deformed than the ground state.

The radioactivity of 76160Os84 and 74156W82 that lie at the two-proton drip line has been measured in an experiment performed at the Accelerator Laboratory of the University of Jyväskylä. The 160Os nuclei were produced using fusion-evaporation reactions induced by a beam of 310 MeV 58Ni ions bombarding a 106Cd target. The 160Os ions were separated in flight using the recoil separator MARA and implanted into a double-sided silicon strip detector, which was used to measure their decays. The α decays of the ground state of 160Os (Eα = 7092(15) keV, t1/2 = 97−32+97 μs) and its isomeric state (Eα = 8890(10) keV, t1/2 = 41−9+15 μs) were measured, allowing the excitation energy of the isomer to be determined as 1844(18) keV. These α-decay properties and the excitation energy of the isomer are compared with systematics. The α decays were correlated with subsequent decays to investigate the β decays of the ground state of 156W, revealing that unlike its isotones, both low-lying isomers were populated in its daughter nuclide, 156Ta. An improved value for the half-life of the proton-decaying high-spin isomeric state in 73156Ta83 of 333−22+25 ms was obtained in a separate experiment using the same experimental systems with a 102Pd target. This result was employed to improve the precision of the half-life determined for 156W, which was measured as 157−34+57 ms.

Three new negative-parity bands have been identified in 120Ba, two of them forming a strongly coupled band. The previously known negative-parity band is significantly extended to high spin, while the lower part of the yrare positive-parity band has been modified. From the analysis of the band properties and comparison with the neighboring nuclei a coherent description of all bands is achieved. In particular, a simple explanation of the evolution of the positive-parity bands at high spin is proposed, including the possible occupation of the ??f7/2[541]1/2??? intruder orbital. Cranked Nilsson-Strutinsky calculations reveal similar quadrupole deformations but different triaxiality of the bands, while particle number conserving cranked shell model calculations qualitatively reproduce the experimental data and support the assigned configurations. The new measured ratios of reduced transition probabilities B(E1)/B(E2) complete the systematics in the 118???124Ba nuclei, exhibiting a decrease with decreasing neutron number, and are compared with the known values in the 116???120Xe nuclei, which are larger. Extended calculations with the quadrupole and octupole collective Hamiltonian based on the relativistic Hartree-Bogoliubov model employing the relativistic DD-PC1 density functional nicely reproduce the decreasing trend towards lower neutron numbers for Ba and Xe nuclei, as well as the larger values in Xe nuclei, but are much larger in amplitude than the experimental values. On the other hand, particle number conserving cranked shell model calculations without octupole deformation overestimate the low-spin values, while those with octupole deformation included reproduce the experimental values in 120Ba, suggesting the possible existence of moderate octupole collectivity in the negative-parity bands of nuclei in this mass region.

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.

The extremely neutron-deficient isotope $^{179}\mathrm{Au}$ has been studied by a combination of in-beam $\ensuremath{\gamma}$-ray and isomeric-decay spectroscopy. For in-beam spectroscopy, the recoil-isomer tagging technique was employed, using the known 3/${2}^{\ensuremath{-}}, {T}_{1/2}=328$ ns isomer. A new rotational band, associated with the unfavored signature band of the $1{h}_{9/2}\ensuremath{\bigoplus}2{f}_{7/2}$ proton-intruder configuration, was revealed. A previously unknown, high-spin isomeric state with an excitation energy of 1743(17) keV and ${T}_{1/2}=2.16(8)\phantom{\rule{4pt}{0ex}}\mathrm{\textmu{}s}$ was discovered. Five decay paths were identified, some of them feeding previously unknown non-yrast excited states, associated with the $1{i}_{13/2}$ proton-intruder configuration. Calculations based on the particle-plus-triaxial-rotor model were performed to interpret the data. On the basis of these calculations, the new $1{h}_{9/2}\ensuremath{\bigoplus}2{f}_{7/2}$ rotational band is interpreted as due to triaxial deformation of the underlying configuration with ${\ensuremath{\beta}}_{2}\ensuremath{\approx}0.26$ and $\ensuremath{\gamma}\ensuremath{\approx}{27}^{\ensuremath{\circ}}$. Observed non-yrast states of the positive-parity $1{i}_{13/2}$ intruder configuration are interpreted as due to triaxial deformation with ${\ensuremath{\beta}}_{2}\ensuremath{\approx}0.26$ and $\ensuremath{\gamma}\ensuremath{\approx}{20}^{\ensuremath{\circ}}$.

Using the fusion-evaporation reaction ^{96}Ru(^{58}Ni,p4n)^{149}Lu and the MARA vacuum-mode recoil separator, a new proton-emitting isotope ^{149}Lu has been identified. The measured decay Q value of 1920(20) keV is the highest measured for a ground-state proton decay, and it naturally leads to the shortest directly measured half-life of 450_{-100}^{+170} ns for a ground-state proton emitter. The decay rate is consistent with l_{p}=5 emission, suggesting a dominant πh_{11/2} component for the wave function of the proton-emitting state. Through nonadiabatic quasiparticle calculations it was concluded that ^{149}Lu is the most oblate deformed proton emitter observed to date.

Two rotational bands are identified in ^119 Cs, one of which having very similar pattern to that of the strongly-coupled π g_9/2[404]9/2^+ band. The properties of the bands with similar patterns extracted from the experimental data are in agreement with a chiral interpretation. Tilted axis cranking covariant density functional theory with pairing correlations and particle-number conserving cranked shell model calculations are employed to determine the deformation and to investigate the band configurations, respectively. It results that the backbending is induced by the rotational alignment of two h_11/2 protons, whose angular momenta reorient from the short to the intermediate axis, in a plane orthogonal to the angular momentum of the strongly-coupled g_9/2 proton which keeps aligned along the long axis. The total spin points in 3D, inducing the breaking of the chiral symmetry. This is the first observation of candidate chiral bands built on a configuration with three protons, one in the strongly coupled [404]9/2^+ orbital which does not change orientation with increasing rotational frequency, and two in the h_11/2 orbital which reorients to the rotation axis. The bands are observed in the transient backbending regime, showing that the chirality in nuclei is a general phenomenon, being robust and present not only in nuclei with nearly maximal triaxiality and pure configurations, but also in nuclei with moderate triaxiality and mixed configurations which gradually evolve from one to three-quasiparticle configurations, like in the backbending region.

The nature of quadrupole and octupole collectivity in 222 Rn was investigated by determining the electric-quadrupole ( E 2) and octupole ( E 3) matrix elements using subbarrier, multistep Coulomb excitation. The radioactive 222 Rn beam, accelerated to 4.23 MeV / u, was provided by the HIE-ISOLDE facility at CERN. Data were collected in the Miniball γ -ray spectrometer following the bombardment of two targets, 120 Sn and 60 Ni. Transition E 2 matrix elements within the ground-state and octupole bands were measured up to 10¯ h and the results were consistent with a constant intrinsic electric-quadrupole moment, 518(11) e fm 2 . The values of the intrinsic electric-octupole moment for the 0 + → 3 − and 2 + → 5 − transitions were found to be respectively 2360 + 300 − 210 e fm 3 and 2300 + 300 − 500 e fm 3 while a smaller value, 1200 + 500 − 900 e fm 3 , was found for the 2 + → 1 − transition. In addition, four excited non-yrast states were identified in this work via γ - γ coincidences. 10.1103/PhysRevC.105.024323

Using the fusion-evaporation reaction ^{96}Ru(^{58}Ni,p4n)^{149}Lu and the MARA vacuum-mode recoil separator, a new proton-emitting isotope ^{149}Lu has been identified. The measured decay Q value of 1920(20) keV is the highest measured for a ground-state proton decay, and it naturally leads to the shortest directly measured half-life of 450_{-100}^{+170}  ns for a ground-state proton emitter. The decay rate is consistent with l_{p}=5 emission, suggesting a dominant πh_{11/2} component for the wave function of the proton-emitting state. Through nonadiabatic quasiparticle calculations it was concluded that ^{149}Lu is the most oblate deformed proton emitter observed to date.

The extremely neutron-deficient isotope Au-179 has been studied by a combination of in-beam gamma-ray and isomeric-decay spectroscopy. For in-beam spectroscopy, the recoil-isomer tagging technique was employed, using the known 3/2(-), T-1/2 = 328 ns isomer. A new rotational band, associated with the unfavored signature band of the 1h(9/2) (R) 2 f(7/2) proton-intruder configuration, was revealed. A previously unknown, high-spin isomeric state with an excitation energy of 1743(17) keV and T-1/2 = 2.16(8) mu s was discovered. Five decay paths were identified, some of them feeding previously unknown non-yrast excited states, associated with the 1i(13/2) proton-intruder configuration. Calculations based on the particle-plus-triaxial-rotor model were performed to interpret the data. On the basis of these calculations, the new 1h(9/2) (R) 2 f(7/2) rotational band is interpreted as due to triaxial deformation of the underlying configuration with 132 ti 0.26 and gamma approximate to 27 degrees. Observed non-yrast states of the positive-parity 1i(13/2) intruder configuration are interpreted as due to triaxial deformation with beta(2) approximate to 0.26 and gamma approximate to 20 degrees.

Prolate-oblate shape coexistence close to the ground state in the strongly-deformed proton-rich A≈120 nuclei is reported for the first time. One of the four reported bands in 119Cs, built on a 11/2− state at 670 keV, consists of nearly degenerate signature partners, and has properties which unequivocally indicate the strongly-coupled πh11/2[505]11/2− configuration associated with oblate shape. Together with the decoupled πh11/2[541]3/2− band built on the 11/2− prolate state at 110 keV, for which a half-life of T1/2=55(5)μs has been measured, the new bands bring evidence of shape coexistence at low spin in the proton-rich strongly deformed A≈120 nuclei, a phenomenon predicted since long time, but not yet observed. Calculations using the particle-number conserving cranked shell model and two dimensional tilted axis cranking covariant density functional theory support and well reproduce the observed oblate and prolate coexisting low-energy states in 119Cs.