keV Transition Research Articles

New readout system of the FATIMA detectors based on Silicon Photomultipliers arrays

We present a new readout system based on large area Silicon Photomultipliers arrays coupled with cylindrical 1.5 × 2” LaBr3(Ce) FATIMA-type crystals. This achieves the fast-timing capabilities of such crystals coupled to the usual Photomultiplier Tubes. Energy calibration was measured with 137Cs and 152Eu standard radioactive sources, while the timing performances were investigated with a 60Co radioactive source. We benchmark our results against the corresponding results obtained with the fast R9779 Photomultiplier tubes and highlight the importance of achieving similar energy and timing performances for nuclear structure experiments. The FWHM energy resolution for the 1.5 × 2” LaBr3(Ce) crystal coupled with the SiPM and PMT was found to be 3.31(2)% and 3.85(1)%, respectively, for the 661.6 keV transition of the 137Cs source. The timing resolution was measured between a conical crystal known for its fast response and a cylindrical crystal coupled to a SiPM or PMT readout. We obtain values of FWHM = 230(1) ps and 232(1) ps, respectively, between the 1173.2-1332.5 keV transitions of the 60Co source. In addition, a temperature effect compensation circuit was developed to maintain a good stability of the gain during long measurements, typical for in-beam/off-beam experiments in nuclear physics.

Decay of a microsecond seniority 3 isomeric state in Hf155

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

Proton Equatorial Pitch Angle Distributions in Jupiter's Inner Magnetosphere

AbstractWe use data from the plasma and energetic particle instruments on the Juno spacecraft, JADE and JEDI, to study the equatorial pitch angle distributions of energetic protons within Jupiter's inner magnetosphere during Juno's prime mission from 2016 to 2021. Averaging over all observations made by Juno within M‐shell bins between M = 6 and M = 30, we find protons at energies between 10 and 50 keV are predominantly field‐aligned at all M‐shells. In contrast, those at energies above 200 keV transition from being predominantly field‐aligned at M = 20 to having pancake‐like distributions at M < 10. We find the observed distributions are consistent either with charge exchange of protons with neutral toroidal clouds, or with adiabatic acceleration of protons originating from Jupiter that are transported inward from the middle magnetosphere.

Experimental determinations of the energy of the 9.4 keV (M1+E2) nuclear transition in 83Kr and the Kr electron binding energies in different matrices by ICES method

An energy value of 9406.3(5) eV was determined for the 9.4 keV (M1+E2) nuclear transition in 83Kr by the internal conversion electron spectrometry method. This value agrees within 1σ with the most precise values determined previously for which their weighted mean amounts to 9405.9(2) eV. A value of 22745.3(2) eV was obtained directly from our experimental data for the energy difference between the 32.1 keV and 9.4 keV transitions in 83Kr. Electron binding energies (related to the Fermi level) on the K, L, and M1,2,3 subshells of Kr implanted into a polycrystalline Pt matrix were also derived. They were found to be lower by weighted mean values of 11.6(4) and 1.7(6) eV compared to those for free Kr atoms and for Kr in an evaporated 83Rb layer on Al backing, respectively, and higher by a weighted mean value of 2.9(2) eV than the binding energies in Kr in an evaporated layer on polycrystalline Pt backing.

On the multipole mixing ratio of the 1066 keV transition from the 0.52 μs isomer of 180Hf

The nucleus 180Hf is one of the most primary examples of an axially symmetric prolate rotor. Combined with the presence of high-K isomers, spectroscopic studies can provide important information on the nature of its single-particle levels. Precise measurements are essential for constraining nuclear models and interpreting the nature of such isomeric states. In this work, the nucleus 180Hf was populated using the proton pick-up reaction 181Ta(11B,12C)180Hf at beam energy of 47 MeV at Horia Hulubei National Institute of Nuclear Physics and Engineering (IFIN-HH). The spin of the 1374 keV state and the mixing ratio of the 1066 keV transition have been measured, the latter with an increased precision compared to the previous value from literature. The presently measured spin of the 1374 keV state, currently assigned a tentative value of (41−), favors one of the two different values that were previously reported. The particular state constitutes the band-head of a rotational band in 180Hf. The measured multipolarity mixing ratio of the inter-band transition 1374→309 keV can provide important information for the testing and constraining of theoretical nuclear models used for the study of the intrinsic properties of 180Hf, as well as its neighboring isotopes.

Nuclear Data Sheets for A=24

Evaluated spectroscopic data and level schemes from radioactive decay and nuclear reaction studies are presented for 24N, 24O, 24F, 24Ne, 24Na, 24Mg, 24Al, and 24Si. This evaluation for A=24 supersedes the earlier one by R. B. Firestone (2007Fi14).Highlights of this evaluation are the following:In 24O, the 7.4- and 7.65-MeV groups reported in 1H(24O,p′) (2012Ts03) and 9Be(26F,nX) (2011Ho05), respectively, are considered as separate states in this evaluation, since the former one was observed to decay by only one neutron emission to 23O, while the latter one by two sequential neutrons to 22O. Based on assigned configurations, the 7.4- and 7.6-MeV groups are tentatively assigned negative and positive parities, respectively. Additional study would be useful to determine if these states are same or different.In 24Na, 2014Fi01 (n,γ) proposed Jπ=(0,1,2)− for 4048.8 keV level based on weaker population from the capture state (Jπ=1+,2+) and mentioned to reexamine the Jπ=0+ assignment, suggested in earlier evaluations (1990En08, 2007Fi02).This evaluation includes the first observation of E0 transition, strength ρ2(E0)=0.380 70, for the 6432 keV transition from 0+ state at 6432 to 0+ g.s. in 24Mg reported in 2020Do10. Authors proposed the first-excited 0+ state of 24Mg to be superdeformed.In 24Al, the excited level energies deduced from (3He,t) measurements reported by different research groups vary significantly and it was not clear if some of those levels were same or different. Additional measurements are needed.

Thermal Neutron Detection in Mixed Neutron-Gamma Fields With Common NaI(Tl) Detectors

NaI(Tl) scintillators can detect thermal neutrons with surprising efficiency, even in the presence of ambient gamma radiation. This is due to a peculiarity of the <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">128</sup> I level scheme. Deexcitation cascades following neutron captures in <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">127</sup> I, a main constituent of NaI with quite large neutron capture cross section, unexpectedly often involve the 167.4 keV state of <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">128</sup> I with 175 ns half-life, which feeds another isomeric level at 137.9 keV having a half-life of 845 ns. The 29.5 keV transition between both levels, as well as the subsequent deexcitation sequence to ground state comprising 137.9 keV sum energy, are almost certainly absorbed in the crystal. Signals including three scintillation pulses within few microseconds, the first one caused by a prompt part of the cascade, the second and third one disclosing 30 and 138 keV energy depositions and characteristic delays, are clearly related to such neutron captures. Double-pulse sequences comprising only the primary pulse and a delayed 138 keV signal are also distinctive but more prone to load-dependent background by random pulse pileups. This article demonstrates neutron detection with a Ø2” <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times2$ </tex-math></inline-formula> ” NaI(Tl) scintillation detector by finding and analyzing such double- and triple-pulse sequences in digitized detector signals. It quantifies effect and background rates as a function of the detector load ranging up to 30 kcps. Complementary measurements with a <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sup> Li codoped Ø2” <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times2$ </tex-math></inline-formula> ” NaI(Tl) (NaIL) scintillator allow relating the neutron detection yield by delayed-coincidence counting to the <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sup> Li capture rate in the same crystal and thus to evaluate prospects and limits of this technique.

β - and γ -spectroscopy study of Pd119 and Ag119

Neutron-rich $^{119}\mathrm{Pd}$ nuclei were produced in fission of natural uranium, induced by 25-MeV protons. Fission fragments swiftly extracted with the Ion Guide Isotope Separation On-Line method were mass separated using a dipole magnet and a Penning trap, providing mono-isotopic samples of $^{119}\mathrm{Pd}$. Their ${\ensuremath{\beta}}^{\ensuremath{-}}$ decay was measured with $\ensuremath{\gamma}\ensuremath{\gamma}$- and $\ensuremath{\beta}\ensuremath{\gamma}$-spectroscopy methods using low-energy germanium detectors and a thin plastic scintillator. Two distinct nuclear-level structures were observed in $^{119}\mathrm{Ag}$, based on the $1/{2}^{\ensuremath{-}}$ and $7/{2}^{+}$ isomers reported previously. The ${\ensuremath{\beta}}^{\ensuremath{-}}$-decay work was complemented by a prompt-$\ensuremath{\gamma}$ study of levels in $^{119}\mathrm{Ag}$ populated in spontaneous fission of $^{252}\mathrm{Cf}$, performed using the Gammasphere array of germanium detectors. Contrary to previous suggestions, our data show that the $1/{2}^{\ensuremath{-}}$ isomer is located below the $7/{2}^{+}$ isomer and is proposed as a new ground state of $^{119}\mathrm{Ag}$ with the $7/{2}^{+}$ isomer excitation energy determined to be 33.4 keV. Our data indicate that there are two $\ensuremath{\beta}$ unstable isomers in $^{119}\mathrm{Pd}$, a proposed ground state of $^{119}\mathrm{Pd}$ with tentative spin $1/{2}^{+}$ or $3/{2}^{+}$ and a half-life of 0.88 s and the other one about 350 keV above, having spin ($11/{2}^{\ensuremath{-}}$) and a half-life of 0.85 s. The higher-energy isomer probably decays to the $1/{2}^{+}$ or $3/{2}^{+}$ ground state via a $\ensuremath{\gamma}$ cascade comprising 18.7-219.8-$\mathrm{X}$-keV transitions. The unobserved isomeric transition with energy $X\ensuremath{\approx}100$ keV probably has an $E3$ multipolarity. Its hindrance factor is significantly lower than for analogous $E3$ isomeric transitions in lighter Pd isotopes, suggesting an oblate deformation of levels in $^{119}\mathrm{Pd}$. Oblate configurations in $^{119}\mathrm{Ag}$ are discussed also.

The first experimental evidence for the (M1 + E2) mixed character of the 9.2 keV transition in 227Th

The 9.2 keV nuclear transition in 227Th was studied in the β−-decay of 227Ac by means of the internal conversion electron spectroscopy to clarify the spin-parity assignment of the ground state and the two lowest excited states of 227Th. The transition multipolarity was proved to be of mixed character M1 + E2 and the spectroscopic admixture parameter δ2(E2/M1)=0.695±0.248 (|δ(E2/M1)|=0.834±0.149) was determined. Nonzero value of δ(E2/M1) questioned the present theoretical interpretation of low-lying levels of 227Th. Calculations performed prefer the 1/2+, 3/2+, and 3/2+ sequence instead of the adopted 1/2+, 5/2+ and 3/2+ one for the 0.0, 9.2, and 24.3 keV levels, respectively.

193Ir Synchrotron-Radiation-Based Mössbauer Spectroscopy for Ir Valence Disproportionation in Ca5Ir3O12

Synchrotron-radiation-based (SR-based) Mössbauer spectroscopy for the 73 keV transition in 193Ir nuclei was successful. 193Ir SR-based Mössbauer spectra of Ca5Ir3O12, as well as those of Ir metal and IrO2 were measured. The results for Ir metal and IrO2 agree with those reported previously. On the other hand, the spectra of Ca5Ir3O12 exhibit temperature dependence. Differences in the observed spectra between 90 and 110 K reflect a change in electronic state at the Ir sites, which correlates with the phase transition reported at 105 K. The results reported in the present work also demonstrate that 193Ir SR-based Mössbauer spectroscopy is a powerful tool for investigating microscopic electronic states in Ir-containing compounds.

Gigagauss magnetic field measurements using Zeeman broadening of Ne-like transitions in highly charged ions.

The measurement of gigagauss magnetic fields using Zeeman broadening of Ne-like transitions in highly charged ions in high energy density plasmas is investigated. The transition in Xe44+ from the (2p5 1/23d3/2)J=1 level to the (2p6)J=0 ground level, designated 3C and having 4.858 keV transition energy, is considered in detail. Ne-like Xe spectra were previously recorded from compressed Xe-filled capsules, and the plasma conditions were determined from spectral line ratios and atomic code modeling. Using the Paschen-Back expression for Zeeman broadening produced by strong magnetic fields and the plasma conditions from the compressed Xe-filled capsule experiments to estimate the competing Stark, Doppler, and turbulence broadenings, it is found that >0.34 GG fields can be determined from spectra recorded by a high-resolution spectrometer having 1eV resolution (5000 resolving power). By scaling the plasma conditions to higher temperatures and densities, the minimum detectable magnetic field is determined for Zeeman broadening of the 3C transition in Ne-like ions up to U82+. Recently developed transmission-crystal spectrometers, employing a cylindrically bent crystal in the Cauchois configuration, have sufficient resolution to determine gigagauss magnetic fields from Zeeman broadening of Ne-like transitions in the 4-18 keV range in Xe44+ to U82+.

Beamline Spectroscopy of Integrated Circuits With Hard X-Ray Transition Edge Sensors at the Advanced Photon Source

At Argonne National Laboratory, we are developing hard X-ray (2 to 20 keV) Transition Edge Sensor (TES) arrays for beamline science. The significantly improved energy resolution provided by superconducting detectors compared to semiconductor-based energy-dispersive detectors, but with better collection efficiency than wavelength-dispersive instruments, will enable greatly improved X-ray emission and absorption spectroscopic measurements. A prototype instrument with 24 microwave-frequency multiplexed pixels is now in testing at the Advanced Photon Source (APS) 1-BM beamline. Initial measurements show an energy resolution ten times better (150 eV compared to < 15 eV) than the silicon-drift detectors currently available to APS beamline users, and in particular demonstrate the ability to resolve closely-spaced emission lines in samples containing multiple transition metal elements, such as integrated circuits. Comparing fluorescence spectra of integrated circuits measured with our TESs at the beamline to those measured with silicon detectors, we find emission lines and elements largely hidden (e.g. Hf alongside Cu) from a semiconductor-based detector but well resolved by a TES. This directly shows the strengths of TES-based instruments in fluorescence mapping.

Improved intensities for theγtransitions withEγ&gt;3MeV fromPb*208

$^{208}\mathrm{Pb}$ is a doubly magic nucleus which has been studied extensively by many experiments and nuclear models. Its properties, such as excitation energies, spins, and parities of the ground and excited states are well known. However, some $\ensuremath{\gamma}$ transitions with ${E}_{\ensuremath{\gamma}}g3$ MeV from the excited states to the ground state in $^{208}\mathrm{Pb}$ have never been observed. The intensities of these $\ensuremath{\gamma}$ transitions are important issues for $0\ensuremath{\nu}\ensuremath{\beta}\ensuremath{\beta}$ decay searches because these transitions can make non-negligible background signals depending on their intensities. We conducted a measurement to search for the 3197.7, 3475.1, and 3708.4 keV transitions, which are emitted from the second, third, and fourth excited states in $^{208}\mathrm{Pb}$, respectively. A 2 kg ${\mathrm{ThO}}_{2}$ sample was measured using a 100% relative efficiency high-purity germanium detector for 39.5 days at Y2L, an underground laboratory in Yangyang, Korea. We improved upper limits for intensities of the 3197.7, 3475.1, and 3708.4 keV $\ensuremath{\gamma}$ transitions as $l1.2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}%, l1.4\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}%$, and $l1.2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}%$, respectively. These upper limits are at least a factor of 19 better than the previous results.

A New Measurement of the 60 keV Emission from Am-241 Using Metallic Magnetic Calorimeters

We report a new measurement of the 60 keV transition from 241Am. It uses a metallic magnetic calorimeter gamma-ray detector calibrated in the region around 60 keV by four accurately known X-rays and gamma rays from the decay of 169Yb. We determine an energy of 59,539.3 ± 0.3 (stat) ± 0.3 (syst) eV, which is 1.6 ± 0.4 eV lower than the current literature value of 59,540.9 ± 0.1 eV. We discuss the sources of this uncertainty and approaches to address them.

X-ray-assisted nuclear excitation by electron capture in optical laser-generated plasmas

X-ray assisted nuclear excitation by electron capture (NEEC) into inner-shell atomic holes in a plasma environment generated by strong optical lasers is investigated theoretically. The considered scenario involves the interaction of a strong optical laser with a solid-state nuclear target leading to the generation of a plasma. In addition, intense x-ray radiation from an X-ray Free Electron Laser (XFEL) produces inner-shell holes in the plasma ions, into which NEEC may occur. As case study we consider the $4.85$-keV transition starting from the 2.4 MeV long-lived $^{\mathrm{93m}}$Mo isomer that can be used to release the energy stored in this metastable nuclear state. We find that the recombination into $2p_{1/2}$ inner-shell holes is most efficient in driving the nuclear transition. Already at few hundred eV plasma temperature, the generation of inner-shell holes can allow optimal conditions for NEEC, otherwise reached for steady-state plasma conditions in thermodynamical equilibrium only at few keV. The combination of x-ray and optical lasers presents two advantages: first, NEEC rates can be maximized at plasma temperatures where the photoexcitation rate remains low. Second, with mJ-class optical lasers and an XFEL repetition rate of $10$ kHz, the NEEC excitation number can reach $\sim 1$ depleted isomer per second and is competitive with scenarios recently envisaged at petawatt-class lasers.

CHEERS Results from NGC 3393. III. Chandra X-Ray Spectroscopy of the Narrow Line Region

Abstract We present spatially resolved Chandra narrow-band imaging and imaging spectroscopy of NGC 3393. This galaxy hosts a Compton-thick Seyfert 2 active galactic nucleus (AGN) with sub-kpc bipolar outflows that are strongly interacting with the circumnuclear gas. We identify narrow-band excess emission associated with the Ne ix 0.905 keV transition (with likely contributions due to intermediate-state iron emission) that points to strong shocks driven by AGN feedback. Imaging spectroscopy resolves outflow-interstellar medium (ISM) interaction sites and the surrounding ISM at ∼100 pc scales, and suggests the presence of a hot AGN wind above the plane at radii beyond the shock sites. The cross-cone shows evidence for reprocessing of photoionization that has passed through gaps in the torus, and also for collisionally excited plasma that may be powered by a shock-confined equatorial outflow. Deep X-ray observations at subarcsecond resolution (such as may be performed very efficiently by Lynx, which would also energetically resolve the complex line emission) are necessary to eliminate model degeneracies and reduce uncertainties in local feedback properties.

Conversion-electron spectroscopy and gamma-gamma angular correlation measurements in 116Sn

The 116Sn nucleus was studied via the $\beta^{-}$ decay of 116In utilizing the $8\pi$ spectrometer and its auxiliary detectors at TRIUMF-ISAC. The resulting K-shell conversion coefficients, K/L ratios, and multipole mixing ratios are presented. The $2_{3}^{+} \rightarrow 2_{1}^{+} 931$ keV and $ 2_{2}^{+} \rightarrow 2_{1}^{+} 819$ keV transition mixing ratios were re-measured and found to be $ \delta = +1.8_{-0.5}^{+0.7}$ and $ -1.83(8)$ , respectively. Newly measured mixing ratios for transitions among the low-lying $ I^{\pi} = 4^{+}$ states in 116Sn, when combined with $\gamma$ -ray intensity data, suggest that the 2529 keV $4_{2}^{+}$ state possesses a neutron broken-pair admixture in addition to its dominant proton 2p-2h component.

Study of the 243Am decay

Gamma-ray emission probabilities for 243Am were published in 1996. Three new gamma transitions were then found: 46.84, 98.36 and 102.02keV. In the last evaluation by the Decay Data Evaluation Project, the emission probabilities of 46.84 and 102.02keV transitions were not included. Alpha-gamma coincidence measurements have been now used to check and revise the values for these two transitions and their emission probabilities. The emissions of the 31.13, 43.53, 74.66, 86.71 and 141.89keV transitions were also studied.

Disintegration rate and gamma-ray emission probability per decay measurement of Cu-64

The procedure followed by the Nuclear Metrology Laboratory (LMN) at the IPEN for the standardization of activity of 64Cu is described. The measurement was carried out in a 4π (PC) β-γ coincidence system. The activity per unit mass of the solution was determined by the extrapolation technique. The events were registered using a Time to Amplitude Converter (TAC) associated with a Multi-channel Analyzer. The gamma-ray emission probability per decay of the 1345.7keV transition of 64Cu determined with a calibrated REGe gamma-ray spectrometer was (0.472 ± 0.010) %, in agreement with the literature.

Improved energy of the 21.5 keV M1 + E2 nuclear transition in 151Eu

Using internal conversion electron spectroscopy, improved energy 21 541.5±0.5 eV was determined for the 21.5keV M1 + E2 nuclear transition in 151Eu populated in the electron capture decay of 151Gd . This value was found to agree well with the present adopted value but is much more accurate. A value of 0.0305±0.0011 derived for the E2 admixture parameter $ \vert\delta(E2/M1)\vert$ from the measured conversion electron line intensities corresponds to the present adopted value. A possible effect of nuclear structure on the multipolarity of the 21.5 keV transition was also investigated.