Γ-ray Intensities Research Articles

Nuclear Data Sheets for A=205

Evaluated nuclear structure and decay data for all nuclei with mass number A=205 (Ir,Pt,Au,Hg,Tl,Pb,Bi, Po,At,Rn,Fr,Ra,Ac) are presented. The experimental data are compiled and evaluated, and best values for level and gamma-ray energies, quantum numbers, lifetimes, γ-ray intensities and transition probabilities, and other nuclear properties are recommended. The reported absolute γ-ray emission probabilities in various decay data sets were calculated using the GABS code (https://www-nds.iaea.org/public/ensdf_pgm/index.htm). Inconsistencies and discrepancies that exist in the literature are discussed. This work supersedes the earlier evaluation by F.G. Kondev (2004Ko28), published in Nuclear Data Sheets 101, 521 (2004).

Coulomb Excitation of Proton-rich N = 80 Isotones at HIE-ISOLDE

A projectile Coulomb-excitation experiment was performed at the radioactive ion beam facility HIE-ISOLDE at CERN. The radioactive 140Nd and 142Sm ions were post accelerated to the energy of 4.62 MeV/A and impinged on a 1.45 mg/cm2-thin 208Pb target. The γ rays depopulating the Coulomb-excited states were recorded by the HPGe-array MINIBALL. The scattered charged particles were detected by a double-sided silicon strip detector in forward direction. Experimental γ-ray intensities were used for the determination of electromagnetic transition matrix elements. Preliminary results for the reduced transition strength of the of 140Nd and a first estimation for 142Sm have been deduced using the Coulomb-excitation calculation software GOSIA. The states of 140Nd and 142Sm show indications of being the main fragment of the proton-neutron mixed-symmetry state.

Nuclear spectrometry of 9.6 h 196Aum2 and the reaction of 197Au with fast neutrons

The neutron activation of gold is the basis of an implosion performance diagnostic at the National Ignition Facility at Lawrence Livermore National Laboratory. In support of this diagnostic, a series of γ-ray spectrometric measurements of the decay of 196Aum2 (Jπ = 12−) was performed to improve the currently accepted literature values of the nuclear data associated with its half-life, γ-ray energies, and γ-ray intensities. It was determined that 196Aum2 decays with a half-life of 9.603 h ± 0.23%. The relative intensities of the γ rays emitted during its decay were also measured, and an absolute decay branch of 0.3352 ± 2.9% was determined for the emission of the 188.2 keV photon, which arises from a nuclear transition whose multipolarity is predominantly M1. Properties of other products arising in the reaction of 197Au with fast neutrons were measured, as were selected production cross sections. The 196Aum2/196Aug isomer ratio measured in the 197Au(n, 2n) reaction at 14.1 MeV was found to be 0.0731 ± 2.6%.

Fluorescent detection of HCl in halogenated solvents via photoinduced electron transfer: towards efficient gamma radiation detection

A series of perylene tetracarboxylic diimides (PDIs) fluorescent molecules are reported to detect the concentration of HCl in non-polar CHCl3 solution. The PET-based fluorescent molecules can eventually be used to identify the intensity of γ-rays.

Two Methods of Determination of Parities of Low-Lying States in 159Gd from Analysis of the γ-ray Intensities from Reaction 158Gd(nres, γ)159Gd

Energy levels and transitions in 159Gd were studied by means of radiative capture of resonance neutrons at 12 isolated resonances of 158Gd. The time-of-flight technique was used on an enriched target at the IBR-30 reactor at JINR Dubna. A total of 80 primary gamma-transitions were recorded and their absolute intensities were determined resulting in the observation of 1/2±, 3/2± levels up to 2.4 MeV. Parities of found levels were recalculated using two methods: the first method consists in analyzing of intensities averaging in 12 resonances and in the second method individual intensities are analyzed. The second method is described for the first time.

Synthetic 26Al emission from galactic-scale superbubble simulations

ABSTRACT Emission from the radioactive trace element 26Al has been observed throughout the Milky Way with the COMPTEL and INTEGRAL satellites. In particular, the Doppler shifts measured with INTEGRAL connect 26Al with superbubbles, which may guide 26Al flows off spiral arms in the direction of Galactic rotation. In order to test this paradigm, we have performed galaxy-scale simulations of superbubbles with 26Al injection in a Milky Way-type galaxy. We produce all-sky synthetic γ-ray emission maps of the simulated galaxies. We find that the 1809 keV emission from the radioactive decay of 26Al is highly variable with time and the observer’s position. This allows us to estimate an additional systematic variability of 0.2 dex for a star formation rate derived from 26Al for different times and measurement locations in Milky Way-type galaxies. High-latitude morphological features indicate nearby emission with correspondingly high-integrated γ-ray intensities. We demonstrate that the 26Al scale height from our simulated galaxies depends on the assumed halo gas density. We present the first synthetic 1809 keV longitude-velocity diagrams from 3D hydrodynamic simulations. The line-of-sight velocities for 26Al can be significantly different from the line-of-sight velocities associated with the cold gas. Over time, 26Al velocities consistent with the INTEGRAL observations, within uncertainties, appear at any given longitude, broadly supporting previous suggestions that 26Al injected into expanding superbubbles by massive stars may be responsible for the high velocities found in the INTEGRAL observations. We discuss the effect of systematically varying the location of the superbubbles relative to the spiral arms.

Activity measurements and determination of nuclear decay data of 166Ho in the MRTDosimetry project

Holmium-166 is a high-energy β−-emitter radionuclide (~ 1.8 MeV) with a short half-life (~26.8h) that offers great potential as an alternative to 90Y for the treatment of liver cancer based on radioembolization. The possibility of quantitative Single Photon Emission Computed Tomography (SPECT) imaging of the main γ-ray emission at 80.6 keV, in addition to strong paramagnetic properties suitable for Magnetic Resonance Imaging (MRI), complement this therapeutic potential. The present paper describes the measurements carried out in three European radionuclide metrology laboratories for primary standardization of 166Ho and new determinations of X- and γ-ray photon-emission intensities in the framework of the European EMPIR project MRTDosimetry. New half-life measurements were also performed.

Numerical simulation and analysis of the characteristics of spatial distribution of induced γ-ray source used for D-D source density measurement

Abstract D-D source has a promising prospect of application in the field of controllable source density logging. However, the spatial distribution of a D-D ‘induced γ-ray source’ varies significantly and such a source is more susceptible to the influence of various formation factors, resulting in relatively low accuracy of density measurement. This study researched the spatial distribution of an induced γ-ray source. First, the principle of D-D controllable source density measurement was analyzed. Second, the generation process of a D-D induced γ-ray source and the spatial distribution under different formation conditions were simulated and studied. Finally, the associated influential factors were summarized. The results indicate that the spatial position and intensity of the induced γ-ray source were susceptible to the influence of various formation factors, such as HI, lithology and salinity. Among these factors, HI had greatest impact on the spatial position of induced γ-ray source and, particularly, when formation HI varied within the range of 0–0.1, the spatial positions of capture γ-rays changed significantly. In addition, as HI increased, the intensity of γ-rays also increased gradually. Formation lithology and salinity had a greater impact on the intensity of induced γ-rays than on the spatial distribution of these γ-rays. For formations of different lithologies, as the types and contents of main elements were different, the intensity of capture γ-rays also varied. This research provides the basic data for correcting the effects on a D-D induced γ-ray source and establishing a method of density measurement using a D-D controllable source.

TPEN: A Triple-foil differential Plunger for lifetime measurements of excited states in Exotic Nuclei

A Triple-foil differential Plunger for Exotic Nuclei (TPEN) has been developed to measure the lifetimes of excited states in nuclei with small production cross-sections. TPEN utilises one target foil and two degrader foils to make differential lifetime measurements: directly determining the decay function and its derivative at a single plunger distance setting. The direct measurement of the decay function and its derivative removes the requirement to measure γ-ray intensities at several target-to-degrader distances, thereby reducing the beam-time required relative to a conventional plunger with a single-degrader foil. This paper describes the commissioning of TPEN in the lifetime measurement of the first excited 4+ state in 156Dy using this differential lifetime technique. The 46(2) ps measured lifetime was found to be in good agreement with the 45.6(5) ps deduced from a previous high-statistics experiment using a conventional two-foil plunger. A comparison between the differential mode with TPEN, and that using TPEN as a conventional two-foil plunger reveals that it achieves the same statistical accuracy with a ∼4-fold reduction in beam-time in the differential mode, for the reaction and experimental setup used in this work. TPEN opens up new opportunities to study exotic nuclei with lower production cross-sections that were previously not accessible.

Formula omitted] decay of 244Am[formula omitted

Decay of 244Amm,g, produced by neutron irradiation of 243Am, has been studied by singles and coincidence measurements of decay γ rays. Two new γ rays of energy 940.54 ± 0.08 and 983.46 ± 0.08 keV have been observed in the decay of 244Amm which suggests a new level of 983.5 keV in 244Cm. This level has been assigned a tentative spin of (1−). In the present studies, uncertainties in the γ-ray intensities of 244Amm,g have been significantly reduced by nearly an order of magnitude for most of the γ rays. The data of half-lives have also been improved. More precise half-lives for 244Amm (T1∕2=26.13 ± 0.43 min) and 244Amg (T1∕2=600.4 ± 1.8 min) have been obtained.

On the origin of the TeV gamma-ray emission from Cygnus X-3

Cygnus X-3 binary system is a famous object studied over the wide range of electromagnetic spectrum. Early detections of ultra-high energy gamma-rays from Cygnus X-3 by Kiel, Havera Park and then by Akeno triggered the construction of several large air shower detectors. Also, Cygnus X-3 has been proposed to be one of the most powerful sources of charged cosmic ray particles in the Galaxy. The results of twenty-year observations of the Cyg X-3 binary at energies 800 GeV - 85 TeV are presented with images, spectra during periods of flaring activity and at low flux periods. The correlation of TeV flux increases with flaring activity at the lower energy range of X-ray and radio emission from the relativistic jets of Cygnus X-3 is found as well as 4.8-hour orbital modulation of TeV γ-ray intensity. Detected modulation of TeV γ-ray emission with orbit and important characteristics of Cyg X-3 such as the high luminosity of the companion star and the close orbit leads to an efficient generation of γ-ray emission through inverse Compton scattering in this object. The different type variability of very high-energy γ-emission and correlation of radiation activity in the wide energy range can provide essential information on the mechanism of particle production up to very high energies.

The potential radio-immunotherapeutic α-emitter 227Th – part II: Absolute γ-ray emission intensities from the excited levels of 223Ra

At the time of publication, radiopharmaceuticals labelled with thorium-227 are in clinical trials in Europe for the treatment of various types of cancer. In part I of this two-part series the primary standardisation of an aqueous solution of 227Th was reported. In part II, the activity derived from the recommended absolute γ-ray emission intensities have been compared to that from the primary standardisation techniques. This comparison showed a negative bias of 4% in the determined activity per unit mass with an 11% spread in the activities determined for the eight most intense γ-ray emissions (Iγ > 1%) from the 227Th α decay. Using the standardised 227Th, measurements of the characteristic γ-ray emissions from the 223Ra excited states were made using a calibrated HPGe γ-ray spectrometer. This has enabled the absolute intensities of 70 γ ray emissions from the 227Th α-decay to be experimentally determined. A significant improvement over the precision of the recommended normalisation scaling factor has been made, with a value of 12.470 (35) % determined. Typically, the precision of the intensities has been improved by an order of magnitude or greater than current recommended values. The correlation matrices for pairs of the most intense γ-ray emission intensities are presented.

Measurement of absolute γ-ray emission probabilities in the decay of 227Ac in equilibrium with its progeny

The emission probabilities of γ rays produced in the 227Ac decay series were determined by high-resolution γ-ray spectrometry of sources with standardised activity. The sources were prepared quantitatively on glass discs by drop deposition of a solution with 227Ac in radioactive equilibrium with its daughter nuclides. Their activity was measured by a primary standardisation technique based on alpha-particle counting at a defined low solid angle. Four laboratories performed γ-ray spectrometry and derived absolute γ-ray intensities. Mean values were calculated and compared with literature data and the currently recommended evaluated data. New values on certain γ-ray emission probabilities are proposed.

Cosmic-rays, gas, and dust in nearby anti-centre clouds

Aims. We have explored the capabilities of dust extinction and γ rays to probe the properties of the interstellar medium in the nearby anti-centre region. In particular, we aim at quantifying the variations of the dust properties per gas nucleon across the different gas phases and different clouds. The comparison of dust extinction and emission properties with other physical quantities of large grains (emission spectral index β, dust colour temperature Tdust, total-to-selective extinction factor RV) helps the theoretical modelling of grains as they evolve from diffuse to dense cloud environments. Methods. We have jointly modelled the γ-ray intensity, recorded between 0.4 and 100 GeV with the Fermi Large Area Telescope (LAT), and the stellar reddening, E(B − V), inferred from Pan-STARRS and 2MASS photometry, as a combination of HI-bright, CO-bright, and ionised gas components. The complementary information from dust reddening and γ rays is used to reveal the gas not seen, or poorly traced, by HI, free-free, and 12CO emissions, namely (i) the opaque HI and diffuse H2 present in the dark neutral medium (DNM) at the atomic-molecular transition, and (ii) the dense H2 to be added where 12CO lines saturate (COsat). We compare the total gas column densities, NH, derived from the γ rays and stellar reddening with those inferred from a similar, previously published analysis of γ rays and of the optical depth of the thermal dust emission, τ353, at 353 GHz. We can therefore compare environmental variations in specific dust reddening, E(B − V)∕NH, and in dust emission opacity (dust optical depth per gas nucleon), τ353∕NH. Results. The gas column densities obtained when combining γ rays with either dust reddening or dust emission compare reasonably well in the atomic and DNM gas phases and over most of the CO-bright phase, but we find localised differences in the dense media (COsat component) due to differences in the two dust tracers. Over the whole anti-centre region, we find an average E(B − V)∕NH ratio of (2.02 ± 0.48) ×10−22 mag cm2, with maximum local variations of about ± 30% at variance with the two to six fold coincident increase seen in emission opacity as the gas column density increases. We show how the specific reddening and opacity vary with the colour temperature and spectral index of the thermal emission of the large grains. Additionally, we find a better agreement between the XCO = N(H2)/WCO conversion factors derived with dust reddening or with γ rays than with those inferred from dust emission, especially towards clouds with large τ353 optical depths. The comparison confirms that the high XCO values found with dust emission are biased by the significant rise in emission opacity inside molecular clouds. Conclusions. In the diffuse medium, we find only small variations in specific reddening, E(B − V)∕NH, compatible with the dispersion in the RV factor reported by other studies. This implies a relatively uniform dust-to-gas mass ratio in the diffuse parts of the anti-centre clouds. The small amplitude of the E(B − V)∕NH variations with increasing NH column density confirms that the large opacity τ353∕NH rise seen towards dense CO clouds is primarily due to changes in dust emissivity. The environmental changes are qualitatively compatible with model predictions based on mantle accretion on the grains and the formation of grain aggregates.

The intensities of [formula omitted]-rays from the decay of 196m2Au

The intensities of γ-rays from the 196m2Au decay adopted in 1998 and 2007 ENSDF evaluations differ up to 20%. Gold samples were irradiated in intensive neutron fluxes with energies up to 35 MeV to produce the isotopes 196Au in all isomeric states. The intensities of gammas from the radioactive decay of the isomer 196m2Au were measured by means of the nuclear γ-ray spectrometry (HPGe detectors) and compared to the existing adopted data.

Investigation of neutron interactions with Ge detectors

Interactions of neutrons with a high-purity germanium detector were studied experimentally and by simulations using the GEANT4 tool. Elastic and inelastic scattering of fast neutrons as well as neutron capture on Ge nuclei were observed. Peaks induced by inelastic scattering of neutrons on 70Ge, 72Ge, 73Ge, 74Ge and 76Ge were well visible in the γ-ray spectra. In addition, peaks due to inelastic scattering of neutrons on copper and lead nuclei, including the well-known peak of 208Pb at 2614.51 keV, were detected. The GEANT4 simulations showed that the simulated spectrum was in a good agreement with the experimental one. Differences between the simulated and the measured spectra were due to the high γ-ray intensity of the used neutron source, physics implemented in GEANT4 and contamination of the neutron source.

Extragalactic diffuse γ-rays from dark matter annihilation: revised prediction and full modelling uncertainties

Recent high-energy data from Fermi-LAT on the diffuse γ-ray background have been used to set among the best constraints on annihilating TeV cold dark matter candidates. In order to assess the robustness of these limits, we revisit and update the calculation of the isotropic extragalactic γ-ray intensity from dark matter annihilation. The emission from halos with masses ⩾ 1010 M⊙ provides a robust lower bound on the predicted intensity. The intensity including smaller halos whose properties are extrapolated from their higher mass counterparts is typically 5 times higher, and boost from subhalos yields an additional factor ∼ 1.5. We also rank the uncertainties from all ingredients and provide a detailed error budget for them. Overall, our fiducial intensity is a factor 5 lower than the one derived by the Fermi-LAT collaboration in their latest analysis. This indicates that the limits set on extragalactic dark matter annihilations could be relaxed by the same factor. We also calculate the expected intensity for self-interacting dark matter in massive halos and find the emission reduced by a factor 3 compared to the collisionless counterpart. The next release of the CLUMPY code will provide all the tools necessary to reproduce and ease future improvements of this prediction.

Studying collective nuclear excitations with fast neutrons: a comparison of 76Ge and 76Se

The low-lying, low-spin level structures of 76Ge and 76Se were studied with the (n,n'γ) reaction. Gamma-ray excitation function and angular distribution measurements were performed, and level spins, level lifetimes, γ-ray intensities, and multipole mixing ratios were determined. Large observed B(E2) values support the identification of low-lying band structures.

95gTc and 96gTc as alternatives to medical radioisotope 99mTc

We studied 95gTc and 96gTc as alternatives to the medical radioisotope 99mTc. 96gTc (95gTc) can be produced by (p, n) reactions on an enriched 96Mo (95Mo) target with a proton beam provided by a compact accelerator such as a medical cyclotron that generate radioisotopes for positron emission tomography (PET). The γ-rays are measured with an electron-tracking Compton camera (ETCC). We calculated the relative intensities of the γ-rays from 95gTc and 96gTc. The calculated γ-ray intensity of a 96gTc (95gTc) nucleus is as high as 63% (70%) of that of a 99mTc nucleus. We also calculated the patient radiation doses of 95gTc and 96gTc, which were larger than that of 99mTc by a factor of 2–3 based on the applied assumptions. A medical PET cyclotron which can provide proton beams with energies of 11–12 MeV and a current of 100 μA can produce 12 GBq (39 GBq) of 96gTc (95gTc) for operation time of 8 h, which can be used for 240 (200) diagnostic scans.

New low-spin states of 122Xe observed via high-statistics β-decay of 122Cs

Excited states of 122Xe were studied via the β+/EC decay of 122Cs with the 8π γ-ray spectrometer at the TRIUMF-ISAC facility. Compton-suppressed HPGe detectors were used for measurements of γ-ray intensities, γγ coincidences, and γ-γ angular correlations. Two sets of data were collected to optimize the decays of the ground (21.2 s) and isomeric (3.7 min) states of 122Cs. The data collected have enabled the observation of about 505 new transitions and about 250 new levels, including 51 new low-spin states. Spin assignments have been made for 58 low-spin states based on the deduced β-decay feeding and γ-γ angular correlation analyses.