Oxygen Isotope and Fluorine Impurity Signatures during the Conversion of Uranium Ore Concentrates to Nuclear Fuel
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37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
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Results for “FLUORINE ISOTOPES”
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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↗
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↗
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↗
Na-22 decay gamma rays from classical novae
NASA Grant NAG 5-1565 has provided support for a program of theoretical research in nuclear astrophysics and related areas, focusing upon the possibility of detecting gamma rays from nearby novae. Particular attention has been given to the evaluation of the theoretical expectations for gamma ray emission from four possible sources: (1) the positron decays of the unstable CNO and fluorine isotopes that are transported to the surface regions of the envelope in the earliest stages of the outbursts; (2) Be-7 decay gamma rays, (3) Na-22 decay gamma rays released in the later stages of the outbursts; and (4) Al-26 decay gamma rays from novae and their possible contribution to Galactic emission. The critical questions of (1) the frequency of occurrence of ONeMg-enriched novae; (2) the expected Galactic distribution of the novae that produce 26Al; and (3) the nature of the observed soft X-ray emission from classical novae, have also been addressed. Considerable progress in research has been achieved on many of these fronts. Brief summaries of the results of several research projects are presented.
Truran, James W.↗
Position-Specific Carbon Isotope Fingerprinting of Fluorinated Organics and Degradation Products
Fluorinated organic compounds are of growing environmental and forensic relevance due to their widespread use in pharmaceuticals, agrochemicals, and consumer products, their environmental persistence, and potential ecological and human health impacts. Elucidating their sources and transformation pathways is therefore a major focus of current research. Stable carbon isotope analysis provides a powerful approach for tracing molecular origins and linking parent compounds to degradation products. Recent isotope measurements have largely relied on mass-spectrometry techniques, which provide only an average isotope ratio across a compound. In this work, we employ a novel nuclear magnetic resonance (NMR) spectroscopy tool to determine position-specific carbon isotope ratios ( 13 C/ 12 C) in organofluorine compounds and their degradation products. This approach enables isotope measurements without combustion or extensive purification and, crucially, resolves ratios at individual carbon positions rather than bulk averages. The resulting intramolecular isotope fingerprints are unique to a molecule’s source. Applied to selected pharmaceuticals and pesticides, these fingerprints allow discrimination of chemically identical compounds. Moreover, we show that the 13 C/ 12 C signature at the fluorinated carbon persists through degradation, demonstrated for lansoprazole and fipronil. The 19 F NMR data produced for the 13 C/ 12 C analyses are also well suited for impurity profiling, providing an additional dimension for fingerprinting fluorinated organics. These findings suggest that position-specific isotope analysis can serve as part of a broader suite of tools for source characterization of organofluorine compounds and their breakdown derivatives, with potential applications in product validation, forensics, and linking these compounds to their breakdown products.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Uranium Single Particle Analysis for Simultaneous Fluorine and Uranium Isotopic Determinations via Laser-Induced Breakdown Spectroscopy/Laser Ablation–Multicollector–Inductively Coupled Plasma–Mass Spectrometry
Uranyl fluoride (UO 2 F 2 ) particles (<20 μm) were subjected to first-of-its-kind analysis via simultaneous laser-induced breakdown spectroscopy (LIBS) and laser ablation multi-collector inductively coupled plasma–mass spectrometry (LA–MC–ICP–MS). Briefly, a nanosecond pulsed high-energy laser was focused onto the sample (particle) surface. In a single laser pulse, the UO 2 F 2 particle was excited/ionized within the microplasma volume, and the emission of light was collected via fiber optics such that emission spectroscopy could be employed for the detection of uranium (U) and fluorine (F). The ablated particle was simultaneously transported into the MC–ICP–MS for high precision isotopic (i.e., 234 U, 235 U, and 238 U) analysis. This method, LIBS/LA–MC–ICP–MS was optimized and employed to rapidly measure 80+ UO 2 F 2 particles, which were subjected to different calcination processes, which results in varying degrees of F loss from the individual particles. In measuring the particles, the average F/U ratios for the populations treated at 100 and 500 °C were 2.78 ± 1.28 and 1.01 ± 0.50, respectively, confirming loss of F through the calcination process. The average 235 U/ 238 U on the particle populations for the 100 and 500 °C were 0.007262 (22) and 0.007231 (23), which was determined to be <0.2% from the expected value. The 234 U/ 238 U ratios on the same particles were 0.000053 (11) and 0.000050 (10) for the 100 and 500 °C, respectively, <10% from the expected value. Notably, each population was analyzed in under 5 min, demonstrating the truly rapid analysis technique presented here in this paper.
38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
Experiments shed new light on nickel-fluorine reactions
Isotopic tracer experiments and scale-impingement experiments show fluorine to be the migrating species through the nickel fluoride scale formed during the fluorination of nickel. This is in contrast to nickel oxide scales, where nickel is the migrating species.
Fischer, J.↗
3'-deoxy-3'-[{sup 18}F]fluorothymidine PET Quantification of Bone Marrow Response to Radiation Dose
Purpose: The purpose of this study was to quantify the relationship of bone marrow response to radiation dose, using 3'-deoxy-3'-[{sup 18}F]fluorothymidine ([{sup 18}F]FLT)-labeled uptake quantified in positron-emission tomography (PET) scans. Methods and Materials: Pre- and post-Week 1 treatment [{sup 18}F]FLT PET images were registered to the CT images used to create the radiation treatment plan. Changes in [{sup 18}F]FLT uptake values were measured using profile data of standardized uptake values (SUVs) and doses along the vertebral bodies located at a field border where a range of radiation doses were present for 10 patients. Data from the profile measurements were grouped into 1 Gy dose bins from 1 to 9 Gy to compare SUV changes for all patients. Additionally, the maximum pretreatment, the post-Week 1 treatment, and the dose values located within the C6-T7 vertebrae that straddled the field edge were measured for all patients. Results: Both the profile and the individual vertebral data showed a strong correlation between SUV change and radiation dose. Relative differences in SUVs between bins >1 Gy and <7 Gy were statistically significant (p < 0.01, two-sample t test). The reduction in SUV was approximately linear until it reached a reduction threshold of 75%-80% in SUV for doses greater than 6 Gy/week for both the dose-binned data and the vertebral maximum SUVs. Conclusions: The change in SUV observed in head and neck cancer patients treated with chemoradiation shows the potential for using [{sup 18}F]FLT PET images for identifying active bone marrow and monitoring changes due to radiation dose. Additionally, the change in [{sup 18}F]FLT uptake observed in bone marrow for different weekly doses suggests potential dose thresholds for reducing bone marrow toxicity.
62 RADIOLOGY AND NUCLEAR MEDICINE↗
Asymptotic normalization of mirror states and the effect of couplings
Assuming that the ratio between asymptotic normalization coefficients of mirror states is model independent, charge symmetry can be used to indirectly extract astrophysically relevant proton capture reactions on proton-rich nuclei based on information on stable isotopes. The assumption has been tested for light nuclei within the microscopic cluster model. In this work we explore the Hamiltonian independence of the ratio between asymptotic normalization coefficients of mirror states when deformation and core excitation is introduced in the system. For this purpose we consider a phenomenological rotor+N model where the valence nucleon is subject to a deformed mean field and the core is allowed to excite. We apply the model to {sup 8}Li/{sup 8}B, {sup 13}C/{sup 13}N, {sup 17}O/{sup 17}F, {sup 23}Ne/{sup 23}Al, and {sup 27}Mg/{sup 27}P. Our results show that, for most studied cases, the ratio between asymptotic normalization coefficients of mirror states is independent of the strength and multipolarity of the couplings induced. The exception is for cases in which there is an s-wave coupled to the ground state of the core, the proton system is loosely bound, and the states have large admixture with other configurations. We discuss the implications of our results for novae.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Nuclear Data Sheets for A = 27
Evaluated spectroscopic data and level schemes from radioactive decay and nuclear reaction studies are presented for {sup 27}F, {sup 27}Ne, {sup 27}Na, {sup 27}Mg, {sup 27}Al, {sup 27}Si, {sup 27}P, and {sup 27}S. This evaluation for A=27 supersedes the earlier evaluation by P.M. Endt (1998En04 and 1990En08).
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Neutron-unbound states in {sup 25,26}F
Neutron-unbound states in {sup 25}F and {sup 26}F were populated via the reactions {sup 9}Be({sup 26}Ne,{sup 24}F + n) and {sup 9}Be({sup 26}Ne,{sup 25}F + n), respectively. A resonance close to the neutron separation energy in {sup 25}F was identified with a decay energy of 28{+-}4 keV. This resonance corresponds to an excited state in {sup 25}F at 4249{+-}116 keV assuming it decays to the ground state of {sup 24}F. Guided by shell-model calculations, a spin and parity of 1/2{sup -} can be assigned to this state. In the spectrum of {sup 26}F, which was produced in a nucleon-exchange reaction, there are indications for an excited state with a decay energy of {approx}270 keV.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
{sup 17}F breakup reactions: a touchstone for indirect measurements
An exclusive study of {sup 17}F breakup reactions has been performed at the FRIBs facility of the Laboratori Nazionali del Sud in Catania (Italy). The experiment has been performed with the aim of testing the accuracy of the Coulomb-breakup indirect technique used to infer radiative-capture cross sections at low energies. This technique has been used in the {sup 7}Be(p,{gamma}){sup 8}B case, but has never been tested. By measuring the breakup of {sup 17}F into {sup 16}O+p, and comparing the inferred cross section for {sup 16}O(p,{gamma}){sup 17}F to direct precise measurements, the influence of E2 transitions and higher-order effects, that are predicted to be significant in Coulomb-breakup reactions, can be evaluated. The first results and preliminary model comparison are reported.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
High accuracy {sup 18}O(p,{alpha}){sup 15}N reaction rate in the 8{center_dot}10{sup 6}-5{center_dot}10{sup 9} K temperature range
The {sup 18}O(p,{alpha}){sup 15}N reaction is of great importance in several astrophysical scenarios, as it influences the production of key isotopes such as {sup 19}F, {sup 18}O and {sup 15}N. In this work, a high accuracy {sup 18}O(p,{alpha}){sup 15}N reaction rate is proposed, based on the simultaneous fit of direct measurements and of the results of a new Trojan Horse experiment. In particular, we have focused on the study of the broad 660 keV 1/2{sup +} resonance. Since {Gamma}{approx}100-300 keV, it strongly influences the nearly-zero-energy region of the cross section by means of the low-energy tail of the resonant contribution and dominates the cross section at higher energies. Here we provide a factor of 2 larger reaction rate above T{approx}0.5 10{sup 9} K based over our new improved determination of its resonance parameters.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Association Between Pulmonary Uptake of Fluorodeoxyglucose Detected by Positron Emission Tomography Scanning After Radiation Therapy for Non-Small-Cell Lung Cancer and Radiation Pneumonitis
Purpose: To study the relationship between fluorodeoxyglucose (FDG) uptake in pulmonary tissue after radical radiation therapy (RT) and the presence and severity of radiation pneumonitis. Methods and Materials: In 88 consecutive patients, {sup 18}F-FDG-positron emission tomography was performed at a median of 70 days after completion of RT. Patients received 60 Gy in 30 fractions, and all but 15 had concurrent platinum-based chemotherapy. RT-induced pulmonary inflammatory changes occurring within the radiation treatment volume were scored, using a visual (0 to 3) radiotoxicity grading scale, by an observer blinded to the presence or absence of clinical radiation pneumonitis. Radiation pneumonitis was retrospectively graded using the Radiation Therapy Oncology Group (RTOG) scale by an observer blinded to the PET radiotoxicity score. Results: There was a significant association between the worst RTOG pneumonitis grade occurring at any time after RT and the positron emission tomograph (PET) radiotoxicity grade (one-sided p = 0.033). The worst RTOG pneumonitis grade occurring after the PET scan was also associated with the PET radiotoxicity grade (one-sided p = 0.035). For every one-level increase in the PET toxicity scale, the risk of a higher RTOG radiation pneumonitis score increased by approximately 40%. The PET radiotoxicity score showed no significant correlation with the duration of radiation pneumonitis. Conclusions: The intensity of FDG uptake in pulmonary tissue after RT determined using a simple visual scoring system showed significant correlation with the presence and severity of radiation pneumonitis. {sup 18}F-FDG-PET may be useful in the prediction, diagnosis and therapeutic monitoring of radiation pneumonitis.
62 RADIOLOGY AND NUCLEAR MEDICINE↗
Usefulness of Interim FDG-PET After Induction Chemotherapy in Patients With Locally Advanced Squamous Cell Carcinoma of the Head and Neck Receiving Sequential Induction Chemotherapy Followed by Concurrent Chemoradiotherapy
Purpose: Induction chemotherapy (ICT) has been used to select patients for organ preservation and determine subsequent treatments in patients with locally advanced squamous cell carcinoma of the head and neck (LASCCHN). Still, the clinical outcomes of LASCCHN patients who showed response to ICT are heterogeneous. We evaluated the efficacy of interim 18-fluoro-2-deoxy-glucose positron emission tomography (FDG-PET) after ICT in this specific subgroup of LASCCHN patients who achieved partial response (PR) after ICT to predict clinical outcomes after concurrent chemoradiotherapy (CCRT). Methods and Materials: Twenty-one patients with LASCCHN who showed PR to ICT by Response Evaluation Criteria In Solid Tumors before definitive CCRT were chosen in this retrospective analysis. FDG-PET was performed before and 2-4 weeks after ICT to assess the extent of disease at baseline and the metabolic response to ICT, respectively. We examined the correlation of the metabolic response by the percentage decrease of maximum standardized uptake value (SUVmax) on the primary tumor or lymph node after ICT or a specific threshold of SUVmax on interim FDG-PET with clinical outcomes including complete response (CR) rate to CCRT, progression-free survival (PFS), and overall survival (OS). Results: A SUVmax of 4.8 on interim FDG-PET could predict clinical CR after CCRT (100% vs. 20%, p = 0.001), PFS (median, not reached vs. 8.5 mo, p < 0.001), and OS (median, not reached vs. 12.0 months, p = 0.001) with a median follow-up of 20.3 months in surviving patients. A 65% decrease in SUVmax after ICT from baseline also could predict clinical CR after CCRT (100% vs. 33.3%, p = 0.003), PFS (median, not reached vs. 8.9 months, p < 0.001) and OS (median, not reached vs. 24.4 months, p = 0.001) of the patients. Conclusion: These data suggest that interim FDG-PET after ICT might be a useful determinant to predict clinical outcomes in patients with LASCCHN receiving sequential ICT followed by CCRT.
62 RADIOLOGY AND NUCLEAR MEDICINE↗
Contrast-Enhanced [{sup 18}F]fluorodeoxyglucose-Positron Emission Tomography/Computed Tomography for Staging and Radiotherapy Planning in Patients With Anal Cancer
Purpose: The practice of surgical staging and treatment of anal cancer has been replaced by noninvasive staging and combined modality therapy. For appropriate patient management, accurate lymph node staging is crucial. The present study evaluated the feasibility and diagnostic accuracy of contrast-enhanced [{sup 18}F]fluoro-2-deoxy-D-glucose ([{sup 18}F]FDG)-positron emission tomography/computed tomography (PET/CT) for staging and radiotherapy planning of anal cancer. Methods and Materials: A total of 22 consecutive patients (median age, 61 years old) with anal cancer underwent complete staging evaluation including physical examination, biopsy of the primary tumor, and contrast-enhanced (ce)-PET/CT. Patients were positioned as they would be for their subsequent radiotherapy. PET and CT images were evaluated independently for detectability and localization of the primary tumor, pelvic and inguinal lymph nodes, and distant metastasis. The stage, determined by CT or PET alone, and the proposed therapy planning were compared with the stage and management determined by ce-PET/CT. Data from ce-PET/CT were used for radiotherapy planning. Results: ce-PET/CT revealed locoregional lymph node metastasis in 11 of 22 patients (50%). After simultaneous reading of PET and CT data sets by experienced observers, 3 patients (14%) were found to have sites of disease not seen on CT that were identified on PET. Two patients had sites of disease not seen on PET that were identified on CT. In summary, 2 patients were upstaged, and 4 patients were downstaged due to ce-PET/CT. However, radiotherapy fields were changed due to the results from ce-PET/CT in 23% of cases compared to CT or PET results alone. Conclusions: ce-PET/CT is superior to PET or CT alone for staging of anal cancer, with significant impact on therapy planning.
62 RADIOLOGY AND NUCLEAR MEDICINE↗