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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2013

Nuclear Data Sheets for A=31

Nuclear spectroscopic information for the known nuclides of mass 31 (F, Ne, Na, Mg, Al, Si, P, S, Cl, Ar) has been evaluated. A useful source of many of the Adopted Levels for {sup 31}P and {sup 31}S is presented in Endt's evaluations (1998En04,1990En08,1978En02,1973EnVA), however all the adopted properties of levels and gamma rays have been re-evaluated in this work. The data sets for reactions and decays, including all available gamma–ray data, are based mostly on the original literature. The 31Mg nuclide is a prime candidate for the study of ‘island-of-inversion’ as its ground state and first excited state can only be explained by intruder orbitals in a deformed shell-model approach. {sup 31}S is of importance in astrophysics rp-process as a possible ‘bottleneck’ nuclide. There are no data available for excited states in {sup 31}F, {sup 31}Ne and {sup 31}Ar. No gamma transitions are known in {sup 31}Cl. For {sup 31}Na, only one excited state is known. The radioactive decay characteristics of {sup 31}F and {sup 31}Ne isotopes have not yet been investigated. The {sup 31}S and {sup 31}Mg nuclei are currently being pursued intensively by various experimental groups, including recent work by Nuclear Astrophysics group at McMaster, the results of which will soon become available.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2021

Highly Perfluorinated Covalent Triazine Frameworks Derived from a Low-Temperature Ionothermal Approach Towards Enhanced CO 2 Electroreduction

Perfluorinated covalent triazine frameworks (F-CTFs) have shown unique features and attractive performance in separation and catalysis. However, state-of-art F-CTFs synthesized via the ZnCl 2 -promoted procedure have quite low fluorine contents due to C-F bond cleavage induced by chloride (a Lewis base) and the harsh conditions deployed (400-700 °C). Fabricating F-CTFs with high fluorine contents (> 30 wt%) remains challenging. Herein, we present a low-temperature ionothermal approach (275 °C) to prepare F-CTFs, which is achieved via polymerization of tetrafluoroterephthalonitrile (TFPN) over the Lewis superacids, e.g., zinc triflimide [Zn(NTf 2 ) 2 ] without side reactions. With low catalyst loading (equimolar), F-CTFs are afforded with high fluorine content (31 wt%), surface area up to 367 m 2 g -1 , and micropores around 1.1 nm. The highly hydrophobic F-CTF-1 exhibits good capability to boost electroreduction of CO 2 to CO, with faradaic efficiency of 95.7% at –0.8 V and high current density (–141 mA cm -2 ) surpassing most of the metal-free electrocatalysts.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Calculations of energies, transition rates, and lifetimes for the fluorine-like isoelectronic sequence with Z=31−35

Employing two state-of-the-art methods, multiconfiguration Dirac–Hartree–Fock and second-order many-body perturbation theory, highly accurate calculations are performed for the lowest 200 fine-structure levels arising from the 2l{sup 7},2l{sup 6}3l{sup ′} and 2l{sup 6}4l{sup ′} configurations of the fluorine-like isoelectronic sequence with Z=31−35. Complete and consistent atomic data, including excitation energies, lifetimes, wavelengths, and E1, E2, M1, M2 line strengths, oscillator strengths, and transition rates among these 200 levels are provided. Comparisons are made between the present two data sets, as well as with other available experimental and theoretical values. The present data are accurate enough for identification and deblending of emission lines involving the n=3,4 levels, and are also useful for modeling and diagnosing fusion plasmas.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2020

Two-neutron halo structure of 31 F

Here, we apply the Gamow shell model to study 25–31 F isotopes. As both internucleon correlations and continuum coupling are properly treated therein, the structure shape of 31 F at large distance can be analyzed precisely. For this, one-nucleon densities, root-mean-square radii, and correlation densities are calculated in neutron-rich fluorine isotopes. It is then suggested that 31 F exhibits a two-neutron halo structure, built from both continuum coupling and nucleon-nucleon correlations.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

Density matrix renormalization group description of the island of inversion isotopes F 28 – 33

Recent experiments have confirmed that the neutron-rich isotopes 28,29 F belong to the so-called island of inversion (IOI), a region of the nuclear chart around Z = 10 and N = 20 where nuclear structure deviates from the standard shell model predictions due to deformation and continuum effects. However, while the general principles leading to the IOI are relatively well understood, the details of the low-lying structure of the exotic fluorine isotopes 28–33 F are basically unknown. In this study, we perform large-scale shell model calculations including continuum states to investigate the properties of the neutron-rich isotopes 25–33 F, from a core of 24 O and using an effective two-body interaction with a small number of adjustable parameters in the central and tensor channels. We develop two models adjusted on experimentally confirmed states in 25,26 O and 25–27 F based on different assumptions concerning the positions of the neutron 0d 3/2 and 1p 3/2 shells, and solve the many-body problem using the density matrix renormalization group (DMRG) method for open quantum systems in an sd–fp model space. We obtain the first detailed spectroscopy of 25–33F in the continuum and show how the interplay between continuum effects and deformation explains the recent data on 28,29 F. Several deformed one- and two-neutron halo states are predicted in 29,31 F, and we provide some information about the possible structure of the heaviest fluorine isotopes. We also suggest several experimental studies of interest to constraint models and test the present predictions.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2017

Synthesis and structure of ruthenium complexes [Ph{sub 3}PCH{sub 2}C{sub 6}H{sub 4}F-4]{sub 2}[RuCl{sub 6}] and [Ph{sub 3}PCH{sub 2}C{sub 6}H{sub 4}F-4][trans-RuCl{sub 4}(dmso-S){sub 2}]

The reaction of (4-fluorobenzyl)triphenylphosphonium chloride with ruthenium(III) chloride hydrate in the presence of hydrochloric acid in dimethyl sulfoxide affords the complex [Ph{sub 3}PCH{sub 2}C{sub 6}H{sub 4}F-4]{sub 2}[RuCl{sub 6}]. In the absence of hydrochloric acid, the reaction gives the complex [Ph{sub 3}PCH{sub 2}C{sub 6}H{sub 4}F-4][trans-RuCl{sub 4}(dmso-S){sub 2}]. The structures of the complexes were studied by {sup 1}H, {sup 19}F, and {sup 31}P NMR spectroscopy and X-ray diffraction.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

New ruthenocene-based ruthenium pincer complex bearing the C{sub 5}Me{sub 4}CF{sub 3} ligand

The first (trifluoromethyl)tetramethylruthenocene-based ruthenium pincer complex RuCl(CO)[{2,5-(Bu_2"tPCH_2)_2C_5H_2}Ru(C{sub 5}Me{sub 4}CF{sub 3})] was synthesized by cyclometallation of the bisphosphine ligand {1,3-(Bu_2"tPCH_2)_2C_5H_2}Ru(C{sub 5}Me{sub 4}CF{sub 3}) with RuCl{sub 2}(DMSO){sub 4} in 2-methoxyethanol in the presence of NEt{sub 3}. The new complex was fully characterized by {sup 1}H, {sup 19}F, {sup 31}P{"1H}, {sup 13}C{"1H} NMR and IR spectroscopy.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Ultrasonic degradation of GenX (HFPO-DA) – Performance comparison to PFOA and PFOS at high frequencies

Sonolytic degradation kinetics of hexafluoropropylene oxide-dimer acid (HFPO-DA or GenX) were studied for the first time at four high ultrasonic frequencies (375, 580, 860 and 1,140kHz) and three power densities (200, 300 and 400W/L), and compared to the degradation of previously studied perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS). The frequency of 580kHz displayed the highest degradation of all three PFAS tested. Within each frequency, the degradation performance increased consistently with increasing power density. Degradation rates were highest for GenX over PFOA to PFOS (k GenX = 0.0501 min -1 , k PFOA = 0.0444 min -1 , k PFOS 0.0153 min -1 ), which is in direct agreement with their reported thermal stability (PFOS > PFOA > GenX). No known by-product formation as expected from the literature on truncation mechanism was detected in the samples (i.e. shorter chain carboxylic acid PFAS). Further, fluorine mass balance experiments at 580kHz and 400W/ L confirmed that GenX defluorinated fastest among the three tested PFAS and had lowest loss of fluorine in the mass balance. Degradation experiments with a mixture of all three PFAS displayed lower degradation rates than the individual experiments, where PFOA exhibited the largest reduction in degradation rate (by 31%), followed by GenX (by 19%), and finally by PFOS (by 17%). Overall, our study demonstrates that ultrasound can provide effective destruction of different PFAS (70-90% fluorine from mitigated PFAS was detected as inorganic fluoride) with a similar energy demand to alternative PFAS treatment methods reported in literature.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Phase equilibria in the NaF-CdO-NaPO{sub 3} system at 873 K and crystal structure and physico-chemical characterizations of the new Na{sub 2}CdPO{sub 4}F fluorophosphate

Isothermal sections of the diagram representing phase relationships in the NaF-CdO-NaPO{sub 3} system have been investigated by solid state reactions and powder X-ray diffraction. This phase diagram investigation confirms the polymorphism of the NaCdPO{sub 4} side component and the structure of the ß high temperature polymorph (orthorhombic, space group Pnma and unit cell parameters a=9.3118(2), b=7.0459(1), c=5.1849(1) Å has been refined. A new fluorophosphate, Na{sub 2}CdPO{sub 4}F, has been discovered and its crystal structure determined and refined from powder X-ray diffraction data. It exhibits a new 3D structure with orthorhombic symmetry, space group Pnma and unit cell parameters a=5.3731(1), b=6.8530(1), c=12.2691(2) Å. The structure is closely related to those of the high temperature polymorph of the nacaphite Na{sub 2}CaPO{sub 4}F and the fluorosilicate Ca{sub 2}NaSiO{sub 4}F but differs essentially in the cationic repartition since the structure is fully ordered with one Na site (8d) and one Cd site (4c). Relationships with other Na{sub 2}M{sup II}PO{sub 4}F (M{sup II}=Mg, Ca, Mn, Fe, Co, Ni) have been examined and the crystal-chemical and topographical analysis of these fluorophosphates is briefly reviewed. IR, Raman, optical and {sup 19}F, {sup 23}Na, {sup 31}P MAS NMR characterizations of Na{sub 2}CdPO{sub 4}F have been investigated. - Graphical abstract: The structure of the compound Na{sub 2}CdPO{sub 4}F, discovered during the study of the phase relationships in the NaF-CdO-NaPO{sub 3} system, has been determined and compared with other Na{sub 2}M{sup II}PO{sub 4}F fluorophosphates. - Highlights: • XRD analysis of the isothermal section of the NaF-CdO-NaPO{sub 3} system at 923 K. • Rietveld refinement of the high temperature polymorph β-NaCdPO{sub 4}. • Crystal structure of the new Na{sub 2}CdPO{sub 4}F fluorophosphate determined from powder XRD. • Crystal structure - composition relationships of Na{sub 2}M{sup II}PO{sub 4}F compounds are reviewed. • IR, Raman, optical and {sup 19}F, {sup 23}Na, {sup 31}P MAS NMR characterizations of Na{sub 2}CdPO{sub 4}F.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Role of quadrupole deformation and continuum effects in the “island of inversion” nuclei 28,29,31 F

The peculiar properties of nuclei in the so-called “island of inversion” around Z = 10 and N = 20 are the focus of current nuclear physics research. Recent studies showed that 28 F has a negative-parity ground state and thus lies within the southern shore of the island of inversion, and 29 F presents a halo structure in its ground state, but it is unclear which effects, such as deformation, shell evolution due to tensor forces, or couplings to the continuum, lead to this situation. Here, we investigate the role of quadrupole deformation and continuum effects on the single-particle structure of 28,29,31 F from a relativistic mean-field approach and show how both phenomena can lead to a negative-parity ground state in 28 F and halo structures in 29,31 F. We solve the Dirac equation in the complex-momentum (Berggren) representation for a potential with quadrupole deformation at the first order obtained from relativistic mean-field calculations using the NL3 interaction and calculate the continuum level densities using the Green’s function method. We extract single-particle energies and widths from the continuum level densities to construct the Nilsson diagrams of 28,29,31 F in the continuum and analyze the evolution of both the widths and occupation probabilities of relevant Nilsson orbitals in 28 F and find that some amount of prolate deformation must be present. In addition, we calculate the density distributions for bound Nilsson orbitals near the Fermi surface in 29,31 F and reveal that, for a quadrupole deformation 0.3 ≤ β 2 ≤ 0.45 (prolate), characteristic halo tails appear at large distances. Using the relativistic mean-field approach in the complex-momentum representation with the Green’s function method, we demonstrate that in neutron-rich fluorine isotopes, while in the spherical case the pf shells are already inverted and close to the neutron emission threshold, a small amount of quadrupole deformation can dramatically reduce the gap between positive- and negative-parity states and increase the role of continuum states, ultimately leading to the negative parity in the ground state of 28 F and the halo structures in 29,31 F.

20 ≤ A ≤ 38↗