Rydberg levels in the atomic spectrum of the element polonium (Po, Z = 84) were investigated using two-step laser resonance ionization spectroscopy in order to probe and determine the first ...ionization potential with high accuracy. As polonium has no stable isotopes, laser resonance ionization spectroscopy was carried out in-source at the Isotope Separator On-Line (ISOL) facility where the radioisotope 206Po was detected after mass separation. Evaluating the convergence of the observed Rydberg series results in a first ionization potential EIP(Po) = 8.418072(3)stat(15)systeV and more than 100 new even-parity Rydberg states belonging to 5 different series. The determined EIP is compared to available literature values and state of the art theoretical atomic many-body calculations.
Display omitted
•Resonance ionization spectroscopy of polonium with proton number Z = 84•Production of the isotope 206-Po at the isotope separator on-line facility TRIUMF•Identification of odd-parity Rydberg levels in the atomic structure of polonium•Determination of the first ionization potential of polonium
Abstract At the FAIR facility, currently under construction at GSI (Darmstadt), a 1.5 AGeV uranium beam with intensities up to 2.5 × 10 11 238 U/spill will impinge on a graphite target at the ...entrance of the Super-FRS for the production of a wide range of rare isotopes by projectile fission and fragmentation. The next generation in-flight magnetic separator Super-FRS, operated up to a magnetic rigidity of 20 Tm with a large angular acceptance (Δ θ = ± 40 mrad, Δ ϕ = ± 20 mrad) and momentum acceptance (Δ p/p = ± 2.5%), requires a new generation of tracking detectors with a position resolution of 0.2 mm ( σ x ) over large detector areas reaching up to 570 cm 2 . Besides gas detectors, planar detectors made of scintillating fibers are an option worth investigating not only because of the comparable material budget but especially for the fast response and high-rate capability. A one-dimensional prototype consisting of 128 fibers with active area of 25.6 × 100 mm 2 coupled to Multi-Pixel-Photon Counters (MPPCs) and readout by FPGA TDC is described together with some recent 197 Au beam test results.
With the rise of neutrino astronomy using large-volume detector arrays, calibration improvements of optical media and photosensors have emerged as significant means to reduce detector systematics. To ...improve understanding of the detector volume and its instrumentation, we developed an absolutely-calibrated, self-monitoring, isotropic, nanosecond, high-intensity calibration light source called “Precision Optical Calibration Module” (POCAM). This, now third iteration, of the instrument was developed for an application in the IceCube Upgrade but, with a modular instrument communications and synchronization backend, can provide a calibration light source standard for any large-volume photodetector array. This work summarizes the functional principle of the POCAM and all related device characteristics as well as its precision calibration procedure. The latter provides fingerprint-characterized instruments with knowledge on absolute and relative behavior of the emitted light pulses as well as their temperature dependencies.
If the mass excess of neutron-deficient nuclei and their neutron-rich mirror partners are both known, it can be shown that deviations of the isobaric mass multiplet equation (IMME) in the form of a ...cubic term can be probed. Such a cubic term was probed by using the atomic mass of neutron-rich magnesium isotopes measured using the TITAN Penning trap and the recently measured proton-separation energies of 29Cl and 30Ar. The atomic mass of 27Mg was found to be within 1.6σ of the value stated in the Atomic Mass Evaluation. The atomic masses of 28,29Mg were measured to be both within 1σ, while being 7 and 33 times more precise, respectively. Using the 29Mg mass excess and previous measurements of 29Cl, we uncovered a cubic coefficient of d = 28(7)keV, which is the largest known cubic coefficient of the IMME. This departure, however, could also be caused by experimental data with unknown systematic errors. Hence there is a need to confirm the mass excess of 28S and the one-neutron separation energy of 29Cl, which have both come from a single measurement. Lastly, our results were compared with ab initio calculations from the valence-space in-medium similarity renormalization group, resulting in a good agreement.
Using the Penning trap mass spectrometer TITAN, we performed the first direct mass measurements of (20,21)Mg, isotopes that are the most proton-rich members of the A = 20 and A = 21 isospin ...multiplets. These measurements were possible through the use of a unique ion-guide laser ion source, a development that suppressed isobaric contamination by 6 orders of magnitude. Compared to the latest atomic mass evaluation, we find that the mass of (21)Mg is in good agreement but that the mass of (20)Mg deviates by 3 σ. These measurements reduce the uncertainties in the masses of (20,21)Mg by 15 and 22 times, respectively, resulting in a significant departure from the expected behavior of the isobaric multiplet mass equation in both the A = 20 and A = 21 multiplets. This presents a challenge to shell model calculations using either the isospin nonconserving universal sd USDA and USDB Hamiltonians or isospin nonconserving interactions based on chiral two- and three-nucleon forces.
With neutrino astronomy on the rise, calibration aspects of large-volume detectors are becoming one of the key targets to boost detector performance. In the scope of the IceCube Upgrade planned for ...the South Pole season of 2022/23, we developed a novel, isotropic, self-monitoring, precision calibration light source. We present the device characteristics as well as first studies of calibration impacts for different detection environments.
The current understanding of light hypernuclei, which are sub-atomic nuclei with strangeness, is being challenged and studied in detail by several European research groups and collaborations. In ...recent years, studies of hypernuclei using high-energy heavy ion beams have reported unexpected results on the three-body hypernuclear state
3
Λ
H, named the hypertriton. For some time, reports of a shorter lifetime and larger binding energy than what was previously accepted have created a puzzling situation for its theoretical description; this is known as the "hypertriton puzzle". With the inclusion of the most recent experimental measurements, the current status of the hypertriton puzzle is evolving. Additionally, the possible neutral bound state of a Λ hyperon with two neutrons, nnΛ, has raised questions about our understanding of the formation of light hypernuclei either in bound or resonance states. These results have initiated several ongoing experimental programs all over the world to study these three-body hypernuclear states precisely. We are studying these light hypernuclear states by employing heavy ion beams at 2
A
GeV on a fixed carbon target with the WASA detector system and the Fragment Separator (FRS) at GSI. The WASA-FRS experimental campaign was performed during the first quarter of 2022, and this paper presents a short overview of the campaign and how it seeks to tackle the hypertriton and nnΛ puzzles. Data analysis is ongoing, and several preliminary results will be reported.
In recent years, there has been an increased concern for the risk of non-target impacts of pesticides. It has been widely acknowledged that weight and volume measures are not adequate proxies for ...assessing this risk, and many pesticide risk indicator models have been developed and are in use throughout the world. They all have their strengths and weaknesses, and here we have evaluated the Norwegian Environmental Risk Indicator (NERI) in relation to the Environmental Impact Quotient (EIQ), both models weighting potential effects on the environment in relation to risk of exposure, and the leaching model Surface Water Attenuation (SWAT). We have utilized reported use of pesticides within two catchments in Norway to be able to compare the model outputs under realistic pest management regimes. In general, the NERI-model gives much weight to substances of long persistence in soil and/or high risk of bioaccumulation, while the EIQ-model risk estimates are largely governed by amount of pesticide used. As the general focus when considering pesticide use and the environment has shifted from purely focusing on reducing amounts to risk reduction, the NERI-model might deliver a more up-to-date output with the more toxic and persistent compounds dominating. However, the absence of mobile pesticides like MCPA from the top of the ranking raises some concern, and points out some of the lacks in such simple models when it comes to use for farmer guidance. They do not include any site specific data on soil characteristics and weather conditions, factors of great importance for pesticide leaching and, hence, governing the risk of exposure. The SWAT-model focuses on the risk of exposure due to leaching, and does not include an effect factor (e.g. toxicity to terrestrial and aquatic organisms). However, for the purpose of farmer guidance, presentations of leaching risk of individual pesticides based on pre-simulated model results under some representative environmental conditions, give the opportunity for an initial screening of the more suitable pesticides regarding risk of exposure.
IDATEN collaboration has been formed by the joint effort between the KHALA in Korea and FATIMA in Europe to perform the fast-timing measurements with the largest LaBr3(Ce) detector array at RIBF of ...RIKEN, Japan. For precise timing detection in a large detector system, the data-acquisition system with complex correlations and large data throughput is required. The results of the benchmark tests for three different systems using standard radioactive sources are compared in the energy resolution, the timing resolution, and the prompt response curves. The characteristics of the three different systems are examined to choose the DAQ systems for KHALA and IDATEN.
Direct lifetime measurements via gamma -gamma coincidences using a fast timing detector array consisting of LaBr3(Ce) scintillators has been applied to determine the lifetime of low-lying states in ...the semimagic (N = 50) nucleus Ru-94. The experiment was carried out as the first in a series of "FAIR-0" experiments with the DESPEC experimental setup at the Facility for Antiproton and Ion Research (FAIR). Excited states in Ru-94 were populated primarily via the beta-delayed proton emission of Pd-95 nuclei, produced in the projectile fragmentation of an 850 MeV/nucleon Xe-124 beam impinging on a 4 g/cm(2) Be-9 target. While the deduced E2 strength for the 2(+) -> 0(+) transition in the yrast cascade follows the expected behavior for conserved seniority symmetry, the intermediate 4(+) -> 2(+) transition exhibits a drastic enhancement of transition strength in comparison with pure-seniority model predictions as well as standard shell model predictions in the f pg proton hole space with respect to doubly magic Sn-100. The anomalous behavior is ascribed to a subtle interference between the wave function of the lowest seniority v = 2, I-pi = 4(+) state and that of a close-lying v = 4 state that exhibits partial dynamic symmetry. In addition, the observed strongly prohibitive 6(+) -> 4(+) transition can be attributed to the same mechanism but with a destructive interference. It is noted that such effects may provide stringent tests of the nucleon-nucleon interactions employed in state-of-the-art theoretical model calculations.
PDF
