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The nuclear structure of the stable nucleus 18476Os has been studied including five newly identified rotational bands built on 2-quasiparticle Kπ=0+, 6−, 8− couplings. The excitation energies of the proposed multi-quasiparticle excitations are in good agreement with predictions of blocked BCS calculations. The interaction responsible for the first band crossing, caused by a high-K tilted 2-neutron configuration, is calculated and a new interpretation presented for the yrast states after the interaction. A second crossing with an aligned s–β band is also reported. The yrast behaviour at high spins is dominated by a wealth of short-lived (nanoseconds and shorter) high-K levels. The low reduced hindrances for intrinsic state decays are discussed, and attributed to the triaxial shapes and fluctuations predicted by configuration-constrained potential-energy-surface calculations. Comparisons with neighbouring nuclei are made. [Copyright &y& Elsevier]

• New 125 I atomic decay emission data from MCDHF calculations are presented. • Simulated Auger electron emission spectra using the new data and the EADL are compared with experiment. • Dose point kernels are simulated with Geant4 using the new atomic data and compared with those obtained from EADL. New 125 I atomic decay emission data of medical interest are presented. The calculations are based on two atomic structure codes that implement the multi-configuration Dirac-Hartree-Fock method. Radiative and non-radiative ransition rates are calculated in this method and then used to generate the atomic deexcitation cascade. Subshell transition rates, level widths and fluorescence yields are compared to the Evaluated Atomic Data Library. Coster-Kronig and Auger electron emission yields are also compared with results from other authors. The comparison with the experimental electron emission spectrum shows that the new calculations can reproduce very well the structure of the K-LL Auger electron peaks and improve the description of the M Auger peaks below 300 eV. The 125 I dose-point kernel is also simulated using the new data, resulting in higher values below 10 nm when compared those obtained with the Evaluated Atomic Data Library. [ABSTRACT FROM AUTHOR]

Excited-state lifetimes were measured by direct fast-timing methods in three N = 125 isotones — 209Po, 211Rn, and 213Ra — near doubly magic 208Pb. These nuclei have a single neutron hole and successively add pairs of protons relative to 208Pb. The first-excited state to ground-state transition, 5 / 2 1 − → 1 / 2 1 − , has almost identical energy in each isotone and can be associated with the single neutron-hole transition ν f 5 / 2 − 1 → ν p 1 / 2 − 1. The extent to which the protons act as spectators is assessed based on the measured transition rates, which show a systematic increase along the isotone chain, and by comparisons with large-basis shell-model calculations. The shell model accounts for some of the increased transition strength but consistently underestimates the experimental values. It also fails to explain the near-constant transition energies. These results suggest emerging collectivity beyond the shell-model valence space and show that the near-constant transition energies are not a consequence of a pure neutron-hole transition, but rather the outcome of complex nucleon-nucleon correlations that increase quadrupole collectivity. [ABSTRACT FROM AUTHOR]

The study of electric monopole (E 0) transitions between two 0 + states is important because the monopole strength carries vital information about the nuclear structure due to its direct link with the mean squared charge radius r 2 and quadrupole deformation parameter β. Therefore, the measurement of internal conversion electrons (ICE) or internal pair formation (IPF) is crucial for E 0 transition studies. Transitions between 0 + states do not change angular momentum. Hence, single-photon emission is forbidden, but can decay by conversion electrons or pair formation and two-photon emission which is mostly negligible. In order to implement E 0 studies at iThemba LABS, an electron spectrometer that uses a solenoidal magnetic field acting as a lens and a Si(Li) detector has been refurbished and characterized using calibration sources of ICE. Figures of merit have been extracted and compared with simulations. The spectrometer coupled with an array of LaBr 3 :Ce detectors and Low Energy Photon Spectrometers (LEPS) was successfully implemented for in-beam experiments. Measurements of internal conversion coefficients (ICC) and monopole strengths extracted from in-beam measurements of 72As, 72Ge, and 72Se are presented. [ABSTRACT FROM AUTHOR]

A new detector array, Solenogam, has been developed at the Australian National University Heavy Ion Accelerator Facility. Coupled initially to the SOLITAIRE 6.5 T, gas-filled, solenoidal separator, and later to an 8 T solenoid, the system enables the study of long-lived nuclear states through γ -ray and conversion-electron spectroscopy in a low-background environment. The detector system is described and results from the commissioning experiments are presented. [ABSTRACT FROM AUTHOR]

Transient-field g-factor measurements in inverse kinematics were performed for the first-excited states of the stable, even isotopes of Ge and Se. The g factors of 74Ge and 74Se were measured simultaneously using a cocktail beam, which eliminates most possible sources of systematic error in a relative g-factor measurement. The results are g(74Se)/g(74Ge)=1.34(7), g(70Ge)/g(74Ge)=1.16(15), g(72Ge)/g(74Ge)=0.92(13), g(76Ge)/g(74Ge)=0.88(5), g(76Se)/g(74Se)=0.96(7), g(78Se)/g(74Se)=0.82(5), g(80Se)/g(74Se)=0.99(7), and g(82Se)/g(74Se)=1.19(6). The measured g-factor ratios are in agreement with ratios from previous measurements, despite considerable variation in previous reported absolute values. The absolute values of the g factors remain uncertain, however, the Rutgers parametrization was used to set the transient-field strength and then compare the experimental g factors with shell-model calculations based on the JUN45 and jj44b interactions. Modest agreement was found between experiment and theory for both interactions. The shell-model calculations indicate that the g(21+) values and trends are determined largely by the balance of the spin carried by orbital motion of the protons. [ABSTRACT FROM AUTHOR]

The conversion electrons from the decay of the 35.5-keV excited state of 125Te following the electron capture decay of 125I have been investigated at high resolution using an electrostatic spectrometer. The penetration parameter λ=-1.2(6) and mixing ratio |δ(E2/M1)|=0.015(2) were deduced by fitting to literature values and present data. The shake probability of the conversion electrons is estimated to be 0.5, more than two times larger than the predicted value of 0.2. [ABSTRACT FROM AUTHOR]

Background: The even cadmium isotopes near the neutron midshell have long been considered among the best examples of vibrational nuclei. However, the vibrational nature of these nuclei has been questioned based on E2 transition rates that are not consistent with vibrational excitations. In the neighboring odd-mass nuclei, the g factors of the low-excitation collective states have been shown to be more consistent with a deformed rotational core than a vibrational core. Moving beyond the comparison of vibrational versus rotational models, recent advances in computational power have made shell-model calculations feasible for Cd isotopes. These calculations may give insights into the emergence and nature of collectivity in the Cd isotopes. Purpose: To investigate the nature of collective excitations in the A ≈ 100 region through experimental and theoretical studies of magnetic moments and electromagnetic transitions in 111Cd. Method: The spectroscopy of 111Cd has been studied following Coulomb excitation. Angular correlation measurements, transient-field g-factor measurements and lifetime measurements by the Doppler-broadened line shape method were performed. The structure of the nucleus was explored in relation to particle-vibration versus particle-rotor interpretations. Large-scale shell-model calculations were performed with the SR88MHJM Hamiltonian. Results: Excited-state g factors have been measured, spin assignments examined, and lifetimes determined. Attention was given to the reported 5/2+ 753-keV and 3/2+ 755-keV states. The 3/2+ 755-keV level was not observed; evidence is presented that the reported 3/2+ state was a misidentification of the 5/2+ 753-keV state. Conclusions: It is shown that the g factors and level structure of 111Cd are not readily explained by the particle-vibration model. A particle-rotor approach has both successes and limitations. The shell-model approach successfully reproduces much of the known low-excitation structure in 111Cd. [ABSTRACT FROM AUTHOR]

The level structure of the odd-odd iodine nucleus 122I has been studied by the 120Sn(7Li, 5n) 122I reaction at Elab = 58 MeV. Two chopped beams from the 14UD (Unit Doubled) tandem heavy-ion accelerator at the Australian National University were used; one was a nanosecond (ns) pulsed-beam with separation of 1.7 microseconds (μs) and the second one was a 60-μs beam separated by 880 μs. Through in-beam and out-of-beam γ-ray spectroscopy, the complex proton-neutron multiplet states, including isomers with half-lives of a few tens of ns to a few tens of μs, have been identified. Collective states based on the proton h11/2 orbital exhibit two kinds of structure depending upon the coupled neutron orbital: a quadrupole vibration when involving the h11/2 orbital and a γ-soft deformed rotation when involving the g7/2 orbital. With spherical shell model and deformed shell-model calculations, the observed level structures are explained. [ABSTRACT FROM AUTHOR]

The level structures of 212Ra and 213Ra have been established via time-correlated γ-ray spectroscopy following the 204Pb(12C,4n)212Ra and 204Pb(13C,4n)213Ra reactions. In 212Ra, levels up to ∼6.2MeV were identified and firm spin-parity assignments were achieved to a Jπ=19+ isomer with a mean life of 31(3) ns. For 213Ra the corresponding values were ∼4.5MeV in excitation energy and Jπ=33/2+. Two isomeric states with Jπ=23/2+, τ=27(3) ns and Jπ=33/2+, τ=50(3) ns were discovered in 213Ra. The experimental data were compared with semiempirical shell-model calculations, which allowed dominant configurations to be assigned to most of the observed levels. [ABSTRACT FROM AUTHOR]

The time differential perturbed angular distribution technique with LaBr3 detectors has been applied to the Iπ=11-/2 isomeric state (Ex=846 keV, τ=107 ns) in 107Cd, which was populated and recoil-implanted into a gadolinium host following the 98Mo(12C, 3n)107Cd reaction. The static hyperfine field strength of Cd recoil implanted into gadolinium was thus measured, together with the fraction of nuclei implanted into field-free sites, under similar conditions as pertained for a previous implantation perturbed angular distribution g-factor measurement on the Iπ=10+ state in 110Cd. The 110Cdg(10+) value was thereby reevaluated, bringing it into agreement with the value expected for a seniority-two νh11/2 configuration. [ABSTRACT FROM AUTHOR]

Using the 168Er (10B, 5n) reaction at a beam energy of 68 MeV, new data have been obtained for the population and decay of a T1/2 = 148 ns, Kπ = 21/2- three-quasiparticle isomer at 1717 keV in 173 Ta. Revised decay energies and intensities have been determined, together with newly observed members of a rotational band associated with the isomer. By comparison with other isomers in the A ≈ 180 deformed region, the 173 Ta isomer properties help to specify the key degrees of freedom that determine K -forbidden transition rates. In particular, when all three quasiparticles are of the same nucleon type, there is a strong dependence of the E2 reduced hindrance factor on the isomer excitation energy. [ABSTRACT FROM AUTHOR]

The only proposed observation of a discrete, hexacontatetrapole (E6) transition in nature occurs from the T_{1/2}=2.54(2)-min decay of ^{53m}Fe. However, there are conflicting claims concerning its γ-decay branching ratio, and a rigorous interrogation of γ-ray sum contributions is lacking. Experiments performed at the Australian Heavy Ion Accelerator Facility were used to study the decay of ^{53m}Fe. For the first time, sum-coincidence contributions to the weak E6 and M5 decay branches have been firmly quantified using complementary experimental and computational methods. Agreement across the different approaches confirms the existence of the real E6 transition; the M5 branching ratio and transition rate have also been revised. Shell model calculations performed in the full fp model space suggest that the effective proton charge for high-multipole, E4 and E6, transitions is quenched to approximately two-thirds of the collective E2 value. Correlations between nucleons may offer an explanation of this unexpected phenomenon, which is in stark contrast to the collective nature of lower-multipole, electric transitions observed in atomic nuclei.

The electric monopole (E0) transition strength ρ^{2} for the transition connecting the third 0^{+} level, a "superdeformed" band head, to the "spherical" 0^{+} ground state in doubly magic ^{40}Ca is determined via e^{+}e^{-} pair-conversion spectroscopy. The measured value ρ^{2}(E0;0&#95;{3}^{+}→0&#95;{1}^{+})=2.3(5)×10^{-3} is the smallest ρ^{2}(E0;0^{+}→0^{+}) found in A<50 nuclei. In contrast, the E0 transition strength to the ground state observed from the second 0^{+} state, a band head of "normal" deformation, is an order of magnitude larger ρ^{2}(E0;0&#95;{2}^{+}→0&#95;{1}^{+})=25.9(16)×10^{-3}, which shows significant mixing between these two states. Large-scale shell-model (LSSM) calculations are performed to understand the microscopic structure of the excited states and the configuration mixing between them; experimental ρ^{2} values in ^{40}Ca and neighboring isotopes are well reproduced by the LSSM calculations. The unusually small ρ^{2}(E0;0&#95;{3}^{+}→0&#95;{1}^{+}) value is due to destructive interference in the mixing of shape-coexisting structures, which are based on several different multiparticle-multihole excitations. This observation goes beyond the usual treatment of E0 strengths, where two-state shape mixing cannot result in destructive interference.

Auger emitting radioisotopes are of great interest in targeted radiotherapy because, once internalised in the tumour cells, they can deliver dose locally to the radiation sensitive targets, while not affecting surrounding cells. Geant4 is a Monte Carlo code widely used to characterise the physics mechanism at the basis of targeted radiotherapy. In this work, we benchmarked the modelling of the emission of Auger electrons in Geant4 deriving from the decay of 123 I, 124 I, 125 I radionuclides against existing theoretical approaches. We also compared Geant4 against reference data in the case of 131 Cs, which is of interest for brachytherapy. In the case of 125 I and 131 Cs, the simulation results are compared to experimental measurements as well. Good agreement was found between Geant4 and the reference data. As far as we know, this is the first study aimed to benchmark against experimental measurements the emission of Auger electrons in Geant4 for radiotherapy applications., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

The cascading 3.21 and 4.44 MeV electric quadrupole transitions have been observed from the Hoyle state at 7.65 MeV excitation energy in ^{12}C, excited by the ^{12}C(p,p^{'}) reaction at 10.7 MeV proton energy. From the proton-γ-γ triple coincidence data, a value of Γ&#95;{rad}/Γ=6.2(6)×10^{-4} was obtained for the radiative branching ratio. Using our results, together with Γ&#95;{π}^{E0}/Γ from Eriksen et al. [Phys. Rev. C 102, 024320 (2020)PRVCAN2469-998510.1103/PhysRevC.102.024320] and the currently adopted Γ&#95;{π}(E0) values, the radiative width of the Hoyle state is determined as Γ&#95;{rad}=5.1(6)×10^{-3}  eV. This value is about 34% higher than the currently adopted value and will impact models of stellar evolution and nucleosynthesis.

Auger electrons emitted after nuclear decay have potential application in targeted cancer therapy. For this purpose it is important to know the Auger electron yield per nuclear decay. In this work we describe a measurement of the ratio of the number of conversion electrons (emitted as part of the nuclear decay process) to the number of Auger electrons (emitted as part of the atomic relaxation process after the nuclear decay) for the case of 125 I. Results are compared with Monte-Carlo type simulations of the relaxation cascade using the BrIccEmis code. Our results indicate that for 125 I the calculations based on rates from the Evaluated Atomic Data Library underestimate the K Auger yields by 20%.

135 La has favorable nuclear and chemical properties for Auger-based targeted internal radiotherapy. Here we present detailed investigations of the production, emissions, and dosimetry related to 135 La therapy. 135 La was produced by 16.5 MeV proton irradiation of metallic nat Ba on a medical cyclotron, and was isolated and purified by trap-and-release on weak cation-exchange resin. The average production rate was 407  ±  19 MBq µA -1 (saturation activity), and the radionuclidic purity was 98% at 20 h post irradiation. Chemical separation recovered  >  98 % of the 135 La with an effective molar activity of 70  ±  20 GBq µmol -1 . To better assess cellular and organ dosimetry of this nuclide, we have calculated the x-ray and Auger emission spectra using a Monte Carlo model accounting for effects of multiple vacancies during the Auger cascade. The generated Auger spectrum was used to calculate cellular S-factors. 135 La was produced with high specific activity, reactivity, radionuclidic purity, and yield. The emission spectrum and the dosimetry are favorable for internal radionuclide therapy.

The aim of this study was to investigate the impact of decay data provided by the newly developed stochastic atomic relaxation model BrIccEmis on dose point kernels (DPKs - radial dose distribution around a unit point source) and S-values (absorbed dose per unit cumulated activity) of 14 Auger electron (AE) emitting radionuclides, namely 67 Ga, 80m Br, 89 Zr, 90 Nb, 99m Tc, 111 In, 117m Sn, 119 Sb, 123 I, 124 I, 125 I, 135 La, 195m Pt and 201 Tl. Radiation spectra were based on the nuclear decay data from the medical internal radiation dose (MIRD) RADTABS program and the BrIccEmis code, assuming both an isolated-atom and condensed-phase approach. DPKs were simulated with the PENELOPE Monte Carlo (MC) code using event-by-event electron and photon transport. S-values for concentric spherical cells of various sizes were derived from these DPKs using appropriate geometric reduction factors. The number of Auger and Coster-Kronig (CK) electrons and x-ray photons released per nuclear decay (yield) from MIRD-RADTABS were consistently higher than those calculated using BrIccEmis. DPKs for the electron spectra from BrIccEmis were considerably different from MIRD-RADTABS in the first few hundred nanometres from a point source where most of the Auger electrons are stopped. S-values were, however, not significantly impacted as the differences in DPKs in the sub-micrometre dimension were quickly diminished in larger dimensions. Overestimation in the total AE energy output by MIRD-RADTABS leads to higher predicted energy deposition by AE emitting radionuclides, especially in the immediate vicinity of the decaying radionuclides. This should be taken into account when MIRD-RADTABS data are used to simulate biological damage at nanoscale dimensions.

To benchmark a Monte Carlo model of the Auger cascade that has been developed at the Australian National University (ANU) against the literature data. The model is applicable to any Auger-electron emitting radionuclide with nuclear structure data in the format of the Evaluated Nuclear Structure Data File (ENSDF). Schönfeld's algorithms and the BrIcc code were incorporated to obtain initial vacancy distributions due to electron capture (EC) and internal conversion (IC), respectively. Atomic transition probabilities were adopted from the Evaluated Atomic Data Library (EADL) for elements with atomic number, Z = 1-100. Atomic transition energies were evaluated using a relativistic Dirac-Fock method. An energy-restriction protocol was implemented to eliminate energetically forbidden transitions from the simulations. Calculated initial vacancy distributions and average energy spectra of 123 I, 124 I, and 125 I were compared with the literature data. In addition, simulated kinetic energy spectra and frequency distributions of the number of emitted electrons and photons of the three iodine radionuclides are presented. Some examples of radiation spectra of individual decays are also given. Good agreement with the published data was achieved except for the outer-shell Auger and Coster-Kronig transitions. Nevertheless, the model needs to be compared with experimental data in a future study.

Auger electrons emitted in nuclear decay offer a unique tool to treat cancer cells at the scale of a DNA molecule. Over the last forty years many aspects of this promising research goal have been explored, however it is still not in the phase of serious clinical trials. In this paper, we review the physical processes of Auger emission in nuclear decay and present a new model being developed to evaluate the energy spectrum of Auger electrons, and hence overcome the limitations of existing computations.

A K(pi)=13+, 280 ns four-quasiparticle isomer in the odd-odd nucleus 174Lu has been identified and characterized. The isomer decays to both K(pi)=7(+) and K(pi)=0(+) rotational bands obtained from the parallel and antiparallel coupling of the proton 7/2+[404] and neutron 7/2+[633] orbitals. K mixing caused by particle-rotation coupling explains the anomalously fast transition rates to the 7+ band but those to the 0+ band are caused by a chance degeneracy between the isomer and a collective state, allowing the mixing matrix element for a large K difference to be deduced.