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.

Fission barrier heights of short-lived nuclei away from line of beta stability are not known reliably. Low-energy fission of 210Fr and 210Ra, produced by (d, p) and (d, n) transfer reaction on the re-accelerated unstable beam 209Fr was investigated at HIE-ISOLDE. Four Timepix3 pixel detectors were installed on the body of the ACTAR TPC demonstrator chamber. Polyethylene converters were used for the detection of fast neutrons. Since no significant background was observed, it was possible to measure the spatial distribution of emitted neutrons reflecting the fission excitation function. Subsequent simulations employing the results of the TALYS code and available data on fission fragment distributions allowed to estimate directly the value of the fission barrier height for the neutron-deficient nucleus 210Fr. This first direct measurement confirmed the reduction of the fission barrier compared to available theoretical calculations by 15-30%.

Fission barrier heights of short-lived nuclei away from line of β stability are not known reliably. Low-energy fission of Fr210 and Ra210, produced by (d,p) and (d,n) transfer reaction on the re-accelerated unstable beam Fr209 was investigated at HIE-ISOLDE. Four Timepix3 pixel detectors were installed on the body of the ACTAR TPC demonstrator chamber. Polyethylene converters were used for the detection of fast neutrons. Since no significant background was observed, it was possible to measure the spatial distribution of emitted neutrons reflecting the fission excitation function. Subsequent simulations employing the results of the code and available data on fission fragment distributions allowed to estimate directly the value of the fission barrier height for the neutron-deficient nucleus Fr210. This first direct measurement confirmed the reduction of the fission barrier compared to available theoretical calculations by 15–30%. Published by the American Physical Society 2024

The excited structure of the single-hole nucleus Sn131 populated by the β− decay of In131 was investigated in detail at the ISOLDE facility at CERN. This new experiment took advantage of isomeric purification capabilities provided by resonant ionization, making it possible to independently study the decay of each isomer for the first time. The position of the first-excited νh11/2 neutron-hole state was confirmed via an independent mass spectroscopy experiment performed at the Ion Guide Isotope Separator On-Line facility at the University of Jyväskylä. The level scheme of Sn131 was notably expanded with the addition of 31 new γ-ray transitions and 22 new excited levels. The γ-emitting excited levels above the neutron separation energy in Sn131 were investigated, revealing a large number of states, which in some cases decay by transitions to other neutron-unbound states. Our analysis showed the dependence between the population of these states in Sn131 and the β-decaying In131 state feeding them. Profiting from the isomer selectivity, it was possible to estimate the direct β feeding to the 3/2+ ground and 11/2− isomeric states, disentangling the contributions from the three indium parent states. This made possible to resolve the discrepancies in logft for first-forbidden transitions observed in previous studies, and to determine the β-delayed neutron decay probability (Pn) values of each indium isomers independently. The first measurement of subnanosecond lifetimes in Sn131 was performed in this work. A short T1/2=18(4)−ps value was measured for the 1/2+ neutron single-hole 332-keV state, which indicates an enhanced l-forbidden M1 behavior for the ν3s1/2−1→ν3d3/2−1 transition. The measured half-lives of high-energy states populated in the β decay of the (21/2+) second isomeric state (In131m2) provided valuable information on transition rates, supporting the interpretation of these levels as core-excited states analogous to those observed in the doubly-magic Sn132. Published by the American Physical Society 2024

Competing configurations, assigned with three different shapes, are mixed at low angular momentum in the neutron-deficient 188Pb nucleus. Here, we present a simultaneous conversion electron and γ-ray in-beam spectroscopic precision measurement employing the sage spectrometer. The level energy of the first excited state, 02+, has been determined at 591(1)keV through direct measurement of conversion electrons. By using the intensity of the observed 02+→01+ transition to the ground state, the feeding of the 02+ state has been determined for the first time, which suggests the 02+ state is the head of the predominantly prolate band. The compositions of the 42+→41+ and 22+→21+ inter-band transitions have been determined, indicating configuration mixing between the bands.

Production of the 55-57Co Co nuclei on nat Ni in photonuclear reactions using bremsstrahlung gamma photon irradiation with end-point energy E gamma max between 35 and 94 MeV has been studied. The experiment was performed at the electron linear accelerator LUE-40 NSC KIPT using the methods of gamma activation and off-line gamma-ray spectroscopy. The obtained experimental flux-averaged cross-sections (a ( E gamma max ) ) agree with the data found in the literature. The theoretical flux-averaged cross- sections (a ( E gamma max ) ) th for the production of 55-57Co Co and 55-57Ni Ni were estimated using the cross-section values a ( E ) from the TALYS1.95 code and bremsstrahlung spectra of gamma photons calculated by GEANT4.9.2. The experimental results for 56,57Co , 57 Co agree with the cumulative (a ( E gamma max ) ) th . For the reactions with the production of 55 Co nuclei, the theoretical values differ from experimental ones.

Bratislava is the capital and largest city of the Slovak Republic. In the Middle Ages, as a part of the Hungarian Empire, it became one of its centers of politics, culture, education and science. In 1467, the first university in the territory of the present Slovakia, named the Academia Istropolitana, was founded in the city of Bratislava. The name of the university was derived from the ancient name of the Danube River, Istros. In 1825 the Hungarian National Learned Society, which is the present Hungarian Academy of Sciences, was founded in Bra ti slava using a donation from count István Széchenyi. After the First World War, Slovakia became a part of Czechoslovakia. Czechoslovakia, as a common state of Czechs and Slovaks needs to be considered as a successful historical project, although it was not democratic during most of its existence. One of the most significant scientific and technological achievements was the design and construction of a nuclear reactor, which was operational at the Jaslovské Bohunice Power Plant. The Slovak Academy of Sciences is the main scientific and research institution in Slovakia, pursuing funda­ mental and applied research. It was founded in 1942, closed after the Second World War, and then re­ established in 1953. In 1955, physical chemist Dionýz Ilkovič, a close colla­ borator of Nobel Prize laureate Jaroslav Heyrovský, founded the Cabinet of Physics at the Slovak Academy of Sciences, which later evolved into the Institute of Physics. Since the begin­ ning, nuclear physics was one of the leading focuses of the Institute. It is worthwhile to mention contributions to the theory of pre­equilibrium nuclear reactions [1], which was developing rapidly in 70’s and 80’s. An important part of experimental program was rel­ ated to neutron physics. Several neutron generators, based on the d + T reaction, were constructed and operated [2]. Ex­ periments were focused on neutron scat­ tering, fast­neutron induced reac tions and national security appli cations. The positron annihilation spectro scopy group has been engaged in research at the inter­ face of several scientific fields, e.g., ma­ terials research, physical chemi stry and applications in biology [3–9]. Important societal changes during the last decade of the 20th century dra­ matically changed the nature of research in Slovakia. First was the Velvet revol­ ution in 1989 that transformed Czecho­ slovakia from communism with a planned economy to democracy with a free market economy. It was followed by a peaceful separation of the federation into two independent states in 1993. Such major changes in a short period of time, had many negative socio­economic consequences. One of these was the ext­ reme reduction of fundamental science funding, leading, e.g., to exodus of many of the best researchers, that mostly never returned. On the other hand, the change in the political system has made travel­ ling abroad much simpler, which opened new collaboration possibilities for Slo­ vak scientists. Slovakia became a member of the European Union in 2004. As a direct consequence, funding through struc­ tural funds of the EU became possible. This allowed significant improvement of scientific infrastructure in the coun­ try. This included also infra struc ture for nuclear physics. Presently, the nuclear physics group at the Institute of Physics has ten permanent staff, complemented with many students. It has extensive international collaboration with CERN, University of Jyväskylä, University of Liverpool, and iThemba Labs and op­ erates its own laboratory, equipped with a Tandetron® accelerator. The ISOLDE facility allows a unique possibility for small groups to run their own experimental program. Although first informal contacts emerged earlier, in 2016 Slovakia became a member of the ISOLDE collaboration. Another im­ portant mile stone was in 2019 when, following the strong suggestion of RECFA, Slovakia joined NuPECC as a full member. Strong efforts of the group from the Institute of Physics were cru­ cial for the establishment of these member ships.

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 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 $\ensuremath{\gamma}\ensuremath{\approx}{20}^{\ensuremath{\circ}}$.

Low-lying states in the odd-Z isotopes Ac-221(89)132 and Pa-225(91)134 have been studied using alpha-particle and alpha gamma-coincidence spectroscopy in the Pa-225 -> Ac-221 -> Fr-217 decay chain. Ground-state spin and parity assignments of I-pi = 5/2(-) are proposed for both Ac-221 and Pa-225, with the odd proton occupying the Omega = 5/2 orbital of the quadrupole-octupole deformed shell model in both nuclei. In Ac-221, excited states in the bands based on the Omega = 5/2 and Omega = 3/2 orbitals have been identified, including proposed parity-doublet states. The results suggest that reflection-asymmetric deformation of the ground state persists in the odd-A members of the isotope chains down to N = 132 for Ac and N = 134 for Pa, before reaching the transitional region at N = 130.

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.

Low-lying states in the odd-$Z$ isotopes $_{\phantom{\rule{3.33333pt}{0ex}}89}^{221}\mathrm{Ac}_{132}$ and $_{\phantom{\rule{3.33333pt}{0ex}}91}^{225}\mathrm{Pa}_{134}$ have been studied using $\ensuremath{\alpha}$-particle and $\ensuremath{\alpha}\ensuremath{\gamma}$-coincidence spectroscopy in the $^{225}\mathrm{Pa}\ensuremath{\rightarrow}^{221}\mathrm{Ac}\ensuremath{\rightarrow}^{217}\mathrm{Fr}$ decay chain. Ground-state spin and parity assignments of ${I}^{\ensuremath{\pi}}$ = ${5/2}^{\ensuremath{-}}$ are proposed for both $^{221}\mathrm{Ac}$ and $^{225}\mathrm{Pa}$, with the odd proton occupying the $\mathrm{\ensuremath{\Omega}}$ = 5/2 orbital of the quadrupole-octupole deformed shell model in both nuclei. In $^{221}\mathrm{Ac}$, excited states in the bands based on the $\mathrm{\ensuremath{\Omega}}$ = 5/2 and $\mathrm{\ensuremath{\Omega}}$ = 3/2 orbitals have been identified, including proposed parity-doublet states. The results suggest that reflection-asymmetric deformation of the ground state persists in the odd-$A$ members of the isotope chains down to $N$ = 132 for Ac and $N$ = 134 for Pa, before reaching the transitional region at $N$ = 130.

oss the physics disciplines, the 186 Pb nucleus is the only known system, where the two first excited states, together with the ground state, form a triplet of zero-spin states assigned with prolate, oblate and spherical shapes. Here we report on a precision measurement where the properties of collective transitions in 186 Pb were determined in a simultaneous in-beam γ -ray and electron spectroscopy experiment employing the recoil-decay tagging technique. The feeding of the 0_2^+ state and the interband 2_2^+→2_1^+ transition have been observed. We also present direct measurement of the energies of the electric monopole transitions from the excited 0 + states to the 0 + ground state. In contrast to the earlier understanding, the obtained reduced transition probability B(E2;2_1^+→0_2^+) value of 190(80) W.u., the transitional quadrupole moment | Q_t(2_1^+→0_2^+)| =7.7 (33) eb and intensity balance arguments provide evidence to reassign the 0_2^+ and 0_3^+ states with predominantly prolate and oblate shape, respectively. Our work demonstrates a step-up in experimental sensitivity and paves the way for systematic studies of electric monopole transitions in this region. These electric monopole transitions probe the nuclear volume in a unique manner and provide unexploited input for development of the next-generation energy density functional models.

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.

Decay spectroscopy of the odd-proton nuclei $$^{249}$$ Md and $$^{251}$$ Md has been performed. High-K isomeric states were identified for the first time in these two nuclei through the measurement of their electromagnetic decay. An isomeric state with a half-life of 2.8(5) ms and an excitation energy $$\ge 910$$ keV was found in $$^{249}$$ Md. In $$^{251}$$ Md, an isomeric state with a half-life of 1.4(3) s and an excitation energy $$\ge 844$$ keV was found. Similarly to the neighbouring $$^{255}$$ Lr, these two isomeric states are interpreted as 3 quasi-particle high-K states and compared to new theoretical calculations. Excited nuclear configurations were calculated within two scenarios: via blocking nuclear states located in proximity to the Fermi surface or/and using the quasiparticle Bardeen–Cooper–Schrieffer method. Relevant states were selected on the basis of the microscopic-macroscopic model with a deformed Woods–Saxon potential. The most probable candidates for the configurations of K-isomeric states in Md nuclei are proposed.

The mean lifetimes of the lowest energy 2(+), 8(+) and 9(-) states in Os-166 have been measured using the recoil distance Doppler-shift method in conjunction with a selective recoil-decay tagging technique. These measurements extend studies into the most neutron-deficient mass region accessible to current experimental methods. The B(E2; 2(+) -> 0(+)) = 7(2) W.u. extracted from these measurements is markedly lower than those observed in the heavier even-mass Os isotopes. The 8(+) and 9(-) states yield reduced transition probabilities that are consistent with single-particle transitions. While these values may indicate a departure from collective structure, the level scheme and the underlying nuclear configurations can also be interpreted in terms of a simple collective picture. This contrasting behaviour suggests an intriguing dichotomy in the description of heavy transitional nuclei.

Using a fusion-evaporation reaction and a gas-filled recoil separator, an isomeric state [T-1/2 = 83(8) mu s] with a most likely spin and parity of 13(+)/2 has been identified in Th-211. The isomeric state is mainly depopulated via a hindered internal M2 transition [B(M2) = 0.0025(5) W.u.], but also a weak alpha-decay branch of 4(3)% was observed. The present observations fit well to the systematic pattern set by the previously identified states of the same spin and parity in this region of the nuclear chart.