A. Ratkiewicz
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View article: Investigation of the \(\gamma \)-ray Properties of the \(2^+\) States in \(^{14}\)C
Investigation of the \(\gamma \)-ray Properties of the \(2^+\) States in \(^{14}\)C Open
The properties of the 2$^+_1$ and 2$^+_2$ excited states in 14C were studied in an experiment conducted at Argonne National Laboratory. A 9Be(6Li,pγ) fusion-evaporation reaction and the GRETINA-ORRUBA setup were employed to populate states…
View article: Abrasion-fission reactions at intermediate energies
Abrasion-fission reactions at intermediate energies Open
The availability of high-intensity, heavy-ion beams coupled to sensitive,\nlarge solid-angleacceptance spectrometers has enabled a detailed examination of\nthe fission fragments produced in induced-fission reactions. The\nabrasion-fission …
View article: <sup>58</sup>Ni(<sup>3</sup>He,t)<sup>58</sup>Cu*(γ) measurements with GODDESS to constrain the astrophysical rate of <sup>57</sup>Ni(p,γ)<sup>58</sup>Cu
<sup>58</sup>Ni(<sup>3</sup>He,t)<sup>58</sup>Cu*(γ) measurements with GODDESS to constrain the astrophysical rate of <sup>57</sup>Ni(p,γ)<sup>58</sup>Cu Open
The observation of γ rays from the decay of 44 Ti in the remnants of core-collapse supernovae (CCSNe) provides crucial information regarding the nucleosynthesis occurring in these events, as 44 Ti production is sensitive to CCSNe condition…
View article: Intermediate-energy Coulomb excitation of 58,60,62Cr: The onset of collectivity toward N=40
Intermediate-energy Coulomb excitation of 58,60,62Cr: The onset of collectivity toward N=40 Open
Intermediate-energy Coulomb excitation measurements were performed on the neutron-rich isotopes 58,60,62Cr. The electric quadrupole excitation strengths, B(E2; 01+→21+), of 60,62Cr are determined for the first time. The results quantify th…
View article: In-beam γ -ray spectroscopy of Mn 63
In-beam γ -ray spectroscopy of Mn 63 Open
Background: Neutron-rich, even-mass chromium and iron isotopes approaching neutron number N=40 have been important benchmarks in the development of shell-model effective interactions incorporating the effects of shell evolution in the exot…
View article: Collectivity at N=40 in neutron-rich Cr64
Collectivity at N=40 in neutron-rich Cr64 Open
Be9-induced inelastic scattering of Fe62,64,66 and Cr60,62,64 was performed at intermediate beam energies. Excited states in Cr64 were measured for the first time. Energies and population patterns of excited states in these neutron-rich Fe…
View article: Ne 19 level structure for explosive nucleosynthesis
Ne 19 level structure for explosive nucleosynthesis Open
Background: Ne19 is an important isotope in nuclear astrophysics due to its role in both the F18(p,α)O15 and O15(α,γ)Ne19 reactions in novae and Type I x-ray bursts, respectively. The energy levels of Ne19 near the α and proton thresholds …
View article: Key Ne 19 States Identified Affecting γ-Ray Emission from F 18 in Novae
Key Ne 19 States Identified Affecting γ-Ray Emission from F 18 in Novae Open
Detection of nuclear-decay γ rays provides a sensitive thermometer of nova nucleosynthesis. The most intense γ-ray flux is thought to be annihilation radiation from the β+ decay of F18, which is destroyed prior to decay by the F18(p,α)O15 …
View article: New γ -ray transitions observed in Ne 19 with implications for the O 15 (α,γ) Ne 19 reaction rate
New γ -ray transitions observed in Ne 19 with implications for the O 15 (α,γ) Ne 19 reaction rate Open
The O15(α,γ)Ne19 reaction is responsible for breakout from the hot CNO cycle in type I x-ray bursts. Understanding the properties of resonances between Ex=4 and 5 MeV in Ne19 is crucial in the calculation of this reaction rate. The spins a…
View article: γ -ray spectroscopy of astrophysically important states in Ca 39
γ -ray spectroscopy of astrophysically important states in Ca 39 Open
Background: Nova explosions synthesize elements up to A≃40, and discrepancies exist between calculated and observed abundances of Ar and Ca created in the explosion. The K38(p,γ)Ca39 reaction rate has been shown to be influential on these …
View article: Political Polarization on Twitter
Political Polarization on Twitter Open
In this study we investigate how social media shape the networked public sphere and facilitate communication between communities with different political orientations. We examine two networks of political communication on Twitter, comprise…
View article: Detecting and Tracking Political Abuse in Social Media
Detecting and Tracking Political Abuse in Social Media Open
We study astroturf political campaigns on microblogging platforms: politically-motivated individuals and organizations that use multiple centrally-controlled accounts to create the appearance of widespread support for a candidate or opinio…
View article: Proton Decay of 21Na for 20Ne Energy Levels
Proton Decay of 21Na for 20Ne Energy Levels Open
The(24)Mg(p,alpha)Na-21 transfer reaction has been previously studied for a spectroscopic study of(21)Na [Chaet al., Phys. Rev. C96, 025810 (2017)]. In this follow-up analysis, the proton decays of the excited states of the radionuclide(21…
View article: Weekly Update -- Scintillators and Mobile Imaging System
Weekly Update -- Scintillators and Mobile Imaging System Open
The Neutron Imaging (NI) project is developing innovative tools that will allow multimodal imaging and high-quality CT imaging of dense objects. To realize these goals a Flat Panel Detector (FPD) has been procured and novel scintillating m…
View article: Using 19F(3He,t)19Ne*(γ) to study astrophysically important levels near the 18F+p threshold
Using 19F(3He,t)19Ne*(γ) to study astrophysically important levels near the 18F+p threshold Open
A direct test of nova explosion models comes from the observation of γ rays created in the decay of radioactive isotopes produced in the nova. One such isotope, 18F, is believed to be the main source of observable γ rays at and below 511 k…
View article: Towards Neutron Capture on Exotic Nuclei: Demonstrating $(d,pγ)$ as a Surrogate Reaction for $(n,γ)$
Towards Neutron Capture on Exotic Nuclei: Demonstrating $(d,pγ)$ as a Surrogate Reaction for $(n,γ)$ Open
The neutron-capture reaction plays a critical role in the synthesis of the elements in stars and is important for societal applications including nuclear power generation and stockpile-stewardship science. However, it is difficult - if not…
View article: Confidence Intervals from Realizations of Simulated Nuclear Data
Confidence Intervals from Realizations of Simulated Nuclear Data Open
Various statistical techniques are discussed that can be used to assign a level of confidence in the prediction of models that depend on input data with known uncertainties and correlations. The particular techniques reviewed in this paper…
View article: Dynamic high energy density plasma environments at the National Ignition Facility for nuclear science research
Dynamic high energy density plasma environments at the National Ignition Facility for nuclear science research Open
We present the generation of dynamic high energy density plasmas in the pico- to nano-second time domain at high-energy laser facilities affords unprecedented nuclear science research possibilities. At the National Ignition Facility (NIF),…
View article: Alternatives to argon for gas stopping volumes in the B194 neutron imager
Alternatives to argon for gas stopping volumes in the B194 neutron imager Open
In a recent experiment at Lawrence Berkeley National Laboratory, the 40Ar(d,p)41Ar excitation function between 3-7 MeV was measured, confirming a previous estimation that there may be an intolerable radiation dose from 41Ar production by s…
View article: Validating (d,p gamma) as a Surrogate for Neutron Capture
Validating (d,p gamma) as a Surrogate for Neutron Capture Open
The r-process is responsible for creating roughly half of the elements heavier than iron. It has recently become understood that the rates at which neutron capture reactions proceed at late times in the rprocess may dramatically affect the…