Atomic Radiation in Nuclear Decay

Auger electrons emitted in nuclear decay offer a unique tool to kill cancer cells at the scale of a DNA molecule. Over the last forty years many aspects of this promising therapeutic tool have been explored, however it is still not in the phase of large

Towards the pair spectroscopy of the Hoyle state in 12C

The triple-alpha process leading to the formation of stable carbon in the Universe is one of the most important nuclear astrophysical processes. The radiative width of the so-called Hoyle state, involving the 7.654 MeV E0 and the 3.2148 MeV E2 transition

Microscopic method for E0 transition matrix elements

We present a microscopic model for electric monopole (E0) transition matrix elements by combining a configuration interaction model for orbital occupations with an energy-density functional model for the singleparticle potential and radial wave functions. The configuration interaction model is used to constrain the orbital occupations for the diagonal and off-diagonal matrix elements. These are used in an energy-density functional calculation to obtain a self-consistent transition density. This density contains the valence contribution, as well as the polarization of the protons by the valence protons and neutrons. We show connections between E0 matrix elements and isomer and isotope shifts of the charge radius. The spin-orbit correction to the charge density is important in some cases. This model accounts for a large part of the data over a wide region of the nuclear chart. It also accounts for the shape of the observed electron scattering form factors. The results depend on the Skyrme parameters used for the energy-density functional and might be used to provide new constraints for them.B.A.B acknowledges U.S. NSF Grant No. PHY-1404442. A.B.G. acknowledges support from NSERC, Canada. T.K. and A.E.S. acknowledge support from Australian Research Council Grant No. DP140102986. We thank George Bertsch and John Wood for their comments on the manuscript

Discovery of a nonyrast Kπ=8+ isomer in Dy162, and the influence of competing K-mixing mechanisms on its highly forbidden decay

The Gd160(Be9,α3n)Dy162 reaction has been used to study high-spin states in Dy162. Pulsed beam conditions were utilized for enhanced isomer sensitivity. An isomer at 2188.1(3) keV with a half-life of 8.3(3) μs has been discovered and assigned Kπ= 8+ with a two-quasineutron configuration. Among 11 γ-ray decay branches, an E2, ΔK=8 transition to the ground-state band was observed with a reduced hindrance of fν=35, agreeing well with systematics correlating fν with the product of the valence neutron and proton numbers (NpNn) over an extended N,Z range. Small deviations from NpNn dependence are analyzed for a range of two-quasiparticle isomer decays and interpreted as arising from a weak dependence on the isomer excitation energy relative to the yrast line

Discovery of isomers in dysprosium, holmium, and erbium isotopes with N = 94 to 97

High-spin states in the 68164Er96 region were studied using 9Be + 160Gd reactions. Pulsed beam conditions were exploited for enhanced sensitivity to delayed γ-ray transitions. New isomers were identified in 161Dy, 163Ho, 162Er, and 165Er. The 162Er isom

Pair conversion spectroscopy of the Hoyle state

The triple-alpha reaction leading to the formation of stable carbon in the Universe is one of the most important nuclear astrophysical processes. The radiative width of the so-called Hoyle state, involving the 7.654 MeV E0 and the 3.2148 MeV E2 transitio

High-resolution conversion electron spectroscopy of the i 125 electron-capture decay

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.This research was made possible by an Australian Research Council Discovery Grant DP140103317. J.T.H.D. acknowledges support of the Australian Government Research Training Program

Spectroscopy and excited-state g factors in weakly collective Cd 111: Confronting collective and microscopic models

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.This research was supported in part by the Australian Research Council Grants No. DP120101417, No. DP130104176, No. DP140102986, No. DP140103317, No. DP170101673, and No. LE150100064. B.J.C., A.A., J.T.H.D., M.S.M.G., and T.J.G. acknowledge support of the Australian Government Research Training Program. Support for the ANU Heavy Ion Accelerator Facility operations through the Australian National Collaborative Research Infrastructure Strategy (NCRIS) program is acknowledged

Absorbed dose evaluation of Auger electron-emitting radionuclides: impact of input decay spectra on dose point kernels and S-values

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 67Ga, 80mBr, 89Zr, 90Nb, 99mTc, 111In, 117mSn, 119Sb, 123I, 124I, 125I, 135La, 195mPt and 201Tl. 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-byevent 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.The authors gratefully acknowledge funding support from the Cancer Research-UK (C5255/ A15935), the Medical Research Council (MC_PC_12004), the Australian Research Council Discovery Grant (no. DP140103317) and the Generalitat de Catalunya (project no. 2014 SGR 846)

Perturbed angular distributions with LaBr3 detectors: The g factor of the first 10+ state in Cd 110 reexamined

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 vh11/2 configuration.This research was supported in part by the Australian Research Council Grants No. DP120101417, No. DP130104176, No. DP140102986, No. DP140103317, No. DP170101673, No. LE150100064, and No. FT100100991, and by The Australian National University Major Equipment Committee Grant No. 15MEC14