16O Nuclei Research Articles

New Version of the Experimental Setup for the Measurement of γ-Quantum Emission Cross Sections in Nuclear Reactions Induced by 14.1 MeV Neutrons

Within the TANGRA project framework, a new experimental setup has been constructed for the measurement of reaction cross sections (n, X, γ) in the interaction of 14.1 MeV neutrons with nuclei. The facility has a special feature: the use of the tagged neutron method. This method enables efficient separation of background and useful events, as well as accurate tracking of neutron flux. Test measurements were performed on 28Si, 12C, and 16O nuclei, and the results showed satisfactory agreement with available experimental data. This paper presents the features of the setup design and the methodology for processing the obtained experimental data

A combined solid-state 1H, 13C, 17O NMR and periodic DFT study of hyperfine coupling tensors in paramagnetic copper(II) compounds

We report solid-state 1H, 13C, and 17O NMR determination of hyperfine coupling tensors (A-tensors) in several paramagnetic Cu(II) (d9, S = 1/2) complexes: trans-Cu(DL-Ala)2·H217O, Cu([1–13C]acetate)2·H2O, Cu([2–13C]acetate)2·H2O, and Cu(acetate)2·H217O. Using these new experimental results and some A-tensor data available in the literature for trans-Cu(L-Ala)2 and K2CuCl4·2H2O, we were able to examine the accuracy of A-tensor computation from a periodic DFT method implemented in the BAND program. We evaluated A-tensors on 1H (I = 1/2), 13C (I = 1/2), 14N (I = 1), 17O (I = 5/2), 39K (I = 3/2), 35Cl (I = 3/2), and 63Cu (I = 3/2) nuclei over a range spanning more than 3 orders of magnitude. We found that the BAND code can reproduce reasonably well the experimental results for both A-tensors and nuclear quadrupole coupling tensors.

Non-empirical description of nuclear collective motion with optimized basis for multi-reference density functional theory

The generator coordinate method (GCM) has been a well-known method to describe nuclear collective motions. In this method, one a priori specifies collective degrees of freedom as inputs of the method based on empirical and/or phenomenological assumptions. We here present an extension of the GCM, in which both the basis Slater determinants and weight factors are optimized in a non-empirical manner. The result for 16O nucleus with the Skyrme functional suggests that a collective coordinate should be determined in a more complex way than what has been assumed so far.

Small-x structure of oxygen and neon isotopes as seen by the Large Hadron Collider

Results on collisions of 16O nuclei performed at the Relativistic Heavy Ion Collider (RHIC) have been presented for the first time at Quark Matter 2023 by the STAR collaboration. 16O+16O collisions are also expected to take place in the near future at the Large Hadron Collider (LHC) at much higher beam energies. We explore the potential of beam-energy-dependent studies for this system to probe small-x dynamics and QCD evolution. We perform 3 + 1D IP-Glasma simulations to predict the rapidity dependence of the initial geometry of light-ion collisions, focusing on 16O+16O and 20Ne+20Ne collisions at √SNN = 70 GeV and 7 TeV. The choice of 20Ne is motivated by its strongly elongated geometry, which may respond differently to the effect of the highenergy evolution compared to the more spherical 16O. We find that smearing induced by soft gluon production at high energy causes mild variations in the initial-state eccentricities as a function of the collision energy. These effects could be resolved in future experiments and deserve further investigation.

Alpha structure of 16O at high excitation energies by 3He+13C nuclear reactions

This work investigates high energy states in the self-conjugate 16O nucleus, through the analysis of 13C(3He,α)12C reactions in the 1.4 2.2 MeV bombarding energy range. The cross-section of the decay channel in which an α particle is emitted in coincidence with a 12C residual nucleus in the Hoyle state, leading to four α particles in the final channel, has been measured thanks to a low-threshold and high-resolution array. The occurrence of two low-spin resonant states is highlighted by the analysis of angular distributions, with Jπ = 2+ and 3−, at respective energies of ≃ 24.1 and 24.5 MeV. In this energy window, the observed branching ratios for the transition involving the emission of the Hoyle state appear to be way larger than calculations based on the barrier penetration alone, pointing out to the possible occurrence of largely clustered high-energy states in 16O.

Потенціал модифікованого методу Томаса - Фермі та його аналітичне представлення на прикладі взаємодії 16О з ізотопами олова 112,114,116,118,120,122,124Sn

Nucleon distribution densities and nucleus-nucleus interaction potentials for the 16O nucleus and 112,114,116,118,120,122,124Sn isotopes were calculated within the framework of the modified Thomas - Fermi method, taking into account all terms to the second-order of ħ in the quasiclassical expansion of kinetic energy. Skyrme forces dependent on the nucleon density were used as nucleon-nucleon interaction. A successful parameterization was found for the obtained potential, which allows to present it in an analytical form.

Estimation of Radiation Damping Rates Using 133Cs, 7Li and 31P Solution NMR Spectroscopy and a Theoretical NMR RASER Model

Radio amplification using stimulated emission of radiation (RASER) effects in the NMR can increase NMR signals over time due to a feedback loop between the sample magnetization and the probe coil coupled with radiation damping (RD). Previously, RD rates had been directly observed only for the 1H, 3He, 17O and 129Xe nuclei. We report that experimental direct measurements of an NMR RASER to determine RD time constants for the three heteronuclei (133Cs (I = 7/2), 7Li (I = 3/2) and 31P (I = 1/2)) in a highly concentrated solution from the NMR RASER emissions using a conventional NMR probe. Under conditions where the RD rate exceeds the transverse relaxation rate (i.e., the NMR RASER condition is fulfilled), we recorded both the transverse NMR RASER response to imperfect inversion and the recovery of longitudinal magnetization. The data were directly evaluated based on the well-known Bloom model as estimated RD rate constants of 8.0, 1.8 and 25 Hz for 133Cs, 7Li and 31P, respectively. The proposed method can be applied to observe RD rate constants for the other nuclei as well.

Study of the nuclear structure for the 18O by using NuShellX@MSU code

In this study, the energy levels, electromagnetic transition probability, and charge density distribution of the 18O nucleus were calculated using the NuShellX@MSU code within the sdpn-shell and using the effective USDEPN and WCPN interactions. The charge density distribution values were also reasonably consistent with existing experimental data. Comparing the theoretical and experimental results indicates that applying the nuclear shell model using the USDEPN and WCPN interactions is successful within the sdpn-shell.

Experimental study of (p, 2p) reactions at 197 MeV on 12C, 16O, 40,48Ca, and 90Zr nuclei leading to low-lying states of residual nuclei

Abstract We have measured the differential cross section and analyzing power for (p, 2p) reactions that lead to discrete states of residual nuclei at an incident energy of 197 MeV for five kinds of target nuclei, 12C, 16O, 40,48Ca, and 90Zr. The data are compared with distorted-wave impulse approximation calculations using two kinds of global optical potentials. The spectroscopic factors obtained from these calculations agree with those determined in (e, e′p) studies within 20%, except for one orbital of the 90Zr nucleus where the distortion effect is much greater than that for the other orbitals of 90Zr and for other target nuclei. We also observed a clear and visibly distinct j-dependence in the analyzing power.

Study of positive parity states form factors for 17O nucleus with Skyrme-Hartree-Fock method

Study of positive parity states form factors for 17O nucleus with Skyrme-Hartree-Fock method

Experimental nuclear charge density and theoretical description of the above-barrier light heavy-ion fusion process* *Supported by the Foundation for the Advancement of Theoretical Physics and Mathematics “BASIS.”

Theoretical modeling of nucleus-nucleus collisions is often based on the nucleus-nucleus potential. One of the advanced methods for constructing this potential is the semi-microscopical double-folding model with M3Y-Paris NN-forces. Proton and neutron densities are significant components of this model. The correct nucleon density (ND) must reproduce the experimental nuclear charge density (NCD). However, those who deal with modeling the fusion process typically disregard this circumstance. We aim to achieve a good description of both the nuclear charge density and above-barrier fusion cross sections of even-even light nuclei with . We consider several versions of NDs available in literature and construct our own approximation for the ND of the even-even spherical nuclei 12C, 16O, and 40Ca, abbreviated as FE-density (Fermi+exponential). We carefully compare the NCDs resulting from different versions of NDs with the experimental NCDs. After finding the nucleus-nucleus potential using the double-folding model with the density dependent M3Y-Paris NN-forces and FE densities, we evaluate the above-barrier fusion cross sections for five reactions, 12C+12C, 12C+16O, 16O+16O, 16O+40Ca, and 40Ca+40Ca, for which experimental data are available. The cross sections are calculated using two approaches: a) the barrier penetration model and b) the trajectory model with surface friction (TM). To find the transmission coefficients for the TM, the Langevin equations are employed. For all considered reactions, our TM typically reproduces the above-barrier experimental cross sections within 10−15%. The only adjustable parameter of the model, the optimal friction strength , is found to be approximately 90 for the light reactions 12C+12C, 12C+16O, and 16O+16O and approximately 15 for the heavy reactions 16O+40Ca and 40Ca+40Ca. The latter findings are in reasonable agreement with the systematics found previously. Thus, the FE-recipe allows highly accurate and simultaneous reproduction of both the nuclear charge density and above-barrier fusion cross sections of five reactions involving 12C, 16O, and 40Ca nuclei.

Cross Sections for Coherent Elastic and Inelastic Neutrino-Nucleus Scattering

The prospects of extracting new physics signals in coherent elastic neutrino–nucleus scattering (CEνNS) processes are limited by the precision with which the underlying nuclear structure physics, embedded in the weak nuclear form factor, is known. We present calculations of charge and weak nuclear form factors and CEνNS cross sections on 12C, 16O, 40Ar, 56Fe and 208Pb nuclei. We obtain the proton and neutron densities, and charge and weak form factors by solving Hartree–Fock (HF) equations with a Skyrme (SkE2) nuclear potential. We validate our approach by comparing 208Pb and 40Ar charge form factor predictions with available elastic electron scattering data. Since CEνNS experiments at stopped-pion sources are also well suited to measure inelastic charged–current and neutral–current neutrino–nucleus cross sections, we also present calculations for these processes, incorporating a continuum Random Phase Approximation (CRPA) description on top of the HF–SkE2 picture of the nucleus. Providing both coherent as well as inelastic cross sections in a consistent framework, we aim at obtaining a reliable and detailed comparison of the strength of these processes in the energy region below 100 MeV. Furthermore, we attempt to gauge the level of theoretical uncertainty pertaining to the description of the 40Ar form factor and CEνNS cross sections by comparing relative differences between recent microscopic nuclear theory and widely-used phenomenological form factor predictions. Future precision measurements of CEνNS will potentially help in constraining these nuclear structure details that will in turn improve prospects of extracting new physics.

Studies of fast protons produced in the reactions of 16O Nuclei incident on emulsion nuclei at 3.7A GeV

• The grey particle multiplicity characteristics, reflects the role of the limiting fragmentation hypothesis. • It is found that the multiplicity distribution of grey particle is independent of the projectile energy or its size. • The multiplicity distribution P(Ng) of the emitted g-particles fit well with the Gauss distribution function, which is both symmetric and platykurtic behavior. Both values of Skewness (S) and Kurtasis (K) are less than zero. • The experimental data shows that the selectivity of N h particle multiplicity as an indication of the impact parameter of nuclear interaction is better than the choice of charged projectile spectator nucleons Q in each event. We report the experimental data of the fast target protons produced in the reaction of 16 O-Em at 3.7A GeV. The emission mechanism of the fast target protons (grey particles with kinetic energy in the range of 26 – 400 MeV) is investigated in terms of multiplicity characteristics. Our experimental data is compared with the corresponding data from the interactions of 12 C, 22 Ne and 28 Si projectiles at nearly the same incident energy. It is found that the multiplicity distribution is independent of the projectile energy or its size. The interaction events were classified in two ways. First, according to the degree of their centrality, depending on the number of the nucleons remaining as spectators Q (stripping nucleons) from the projectile. The second way, the interactions are classified according to the target size (N h – parameter). At various groups of events, the higher moments of the multiplicity distributions were calculated statistically. The experimental data shows that the selectivity of N h particle multiplicity as an indication of the impact parameter of nuclear interaction is better than the choice of charged projectile spectator nucleons Q in each event.

DIGITAL PROCESSING OF PHOTOS FROM A 4π TRACK DETECTOR

A measuring complex with a digital data bank of stereo photos of photonuclear reactions on 4He, 12C, 14N, and 16O nuclei got from a 4 track detector has been created. The file name was formatted into a certain type of record, which included information about the experiment and the position in the data bank. A graphical application was presented that allowed semi-automatic determination of points along tracks of different lengths and curvatures. Methods and algorithms allowing to transfer into the camera system and perform event reconstruction were developed. Additional programs for the physical analysis of the reconstructed events and the graphical representation of the obtained results were created.

On the effectiveness of proton boron fusion therapy (PBFT) at cellular level

The present work introduced a framework to investigate the effectiveness of proton boron fusion therapy (PBFT) at the cellular level. The framework consisted of a cell array generator program coupled with PHITS Monte Carlo package with a dedicated terminal-based code editor that was developed in this work. The framework enabled users to model large cell arrays with normal, all boron, and random boron filled cytoplasm, to investigate the underlying mechanism of PBFT. It was found that alpha particles and neutrons could be produced in absence of boron mainly because of nuclear reaction induced by proton interaction with 16O, 12C and 14N nuclei. The effectiveness of PBFT is highly dependent on the incident proton energy, source size, cell array size, buffer medium thickness layer, concentration and distribution of boron in the cell array. To quantitatively assess the effectiveness of PBFT, of the total energy deposition by alpha particle for different cases were determined. The number of alpha particle hits in cell cytoplasm and nucleus for normal and 100 ppm boron were determined. The obtained results and the developed tools would be useful for future development of PBFT to objectively determine the effectiveness of this treatment modality.

Demonstrative measurement of proton-nuclear reaction by deconvolving the prompt gamma-ray spectra

In proton therapy, there has been an increasing demand for measuring the employed dose distribution to improve treatment accuracy and quality. One method of estimating radiation dose in real time is to visualize the prompt gamma rays emitted during nuclear reactions between protons and nuclei in the patient’s body. However, this is difficult without accurate measurements of nuclear cross sections, that cover a 10–100 MeV energy range. Herein, we propose a novel method for determining cross section of low-energy protons with 12C and 16O by measuring the prompt gamma rays emitted from stacked slab phantoms placed along the proton path. These emitted gamma rays provide direct information on the nuclear reactions occurring at different proton energies. By applying an iterative inference using the response matrix, the contamination of various prompt gamma rays can be resolved; thus, the cross sections of various reactions were obtained at arbitrary proton energies. As a first step to this study, we applied this method to measure the nuclear reaction of protons with 12C and 16O nuclei, which are the major elements constituting the human body. The cross section of the 12C(p,p)12C∗ reaction, which produces a prominent gamma-ray peak at 4.4 MeV, reproduced the one in literature well, supporting the validity of the proposed method. Furthermore, we show that even weak prompt gamma rays can be resolved for a wide range of proton energies below 70 MeV, for which no cross sectional data have been reported so far.

Distance analysis of elastic scattering data of light projectiles on 27Al target

The strong synergy between nuclear structure and reactions mechanism has allowed the observation of cluster effects in the elastic scattering process. In this work we present an alternative phenomenological analysis on the angular distributions for elastic scattering induced by tightly-bound (12C, 16O), weakly-bound (6Li, 7Li, 9Be), and exotic (6He) nuclei on light 27Al target at energies close to the Coulomb barrier. The reported and published angular distributions for these systems were converted from cross sections as a function of angle to cross sections as a function of the distance of closest approach. From these new plots, it is now possible to extract the critical-interaction and strong-absorption distances. Larger values for the critical distances were obtained for the exotic and weakly-bound nuclei as compared to those corresponding to tightly-bound 12C and 16O nuclei.

Calculation of the Magnetic Dipole and Electric Quadrupole Moments of some Sodium Isotopes using Shell Model with Skyrme Interaction

In the present work, the magnetic dipole and electric quadrupole moments for some sodium isotopes have been calculated using the shell model, considering the effect of the two-body effective interactions and the single-particle potentials. These isotopes are; 21Na (3/2+), 23Na (3/2+), 25Na (5/2+), 26Na (3+), 27Na (5/2+), 28Na (1+) and, 29Na (3/2+). The one-body transition density matrix elements (OBDM) have been calculated using the (USDA, USDB, HBUMSD and W) two-body effective interactions carried out in the sd-shell model space. The sd shell model space consists of the active 2s1/2, 1d5/2, and1d1/2 valence orbits above the inert 16O nucleus core, which remains closed. Skyrme interaction was implemented to generate the single-particle matrix elements with Hartree-Fock approximation and compared with those of harmonic oscillator and Wood-Saxon potentials. From the outcome of our investigation, it is possible to conclude that the shell model calculations with Skyrme-type interaction give a reasonable description for most of the selected Na isotopes. No significant difference was noticed for the magnetic dipole moments and electric quadrupole moments with experimental data, where all signs for the experimental data are reproduced correctly.

17O Labeling Reveals Paired Active Sites in Zeolite Catalysts

Current needs for extending zeolite catalysts beyond traditional gas-phase hydrocarbon chemistry demand detailed characterization of active site structures, distributions, and hydrothermal impacts. A broad suite of homonuclear and heteronuclear NMR correlation experiments on dehydrated H-ZSM-5 catalysts with isotopically enriched 17O frameworks reveals that at least two types of paired active sites exist, the amount of which depends on the population of fully framework-coordinated tetrahedral Al (Al(IV)-1) and partially framework-coordinated tetrahedral Al (Al(IV)-2) sites, both of which can be denoted as (SiO)4-n-Al(OH)n. The relative amounts of Al(IV)-1 and Al(IV)-2 sites, and subsequent pairing, cannot be inferred from the catalyst Si/Al ratio, but depend on synthetic and postsynthetic modifications. Correlation experiments demonstrate that, on average, acidic hydroxyl groups from Al(IV)-1/Al(IV)-2 pairs are closer to one another than those from Al(IV)-1/Al(IV)-1 pairs, as supported by computational DFT calculations. Through-bond and through-space polarization transfer experiments exploiting 17O nuclei reveal a number of different acidic hydroxyl groups in varying Si/Al catalysts, the relative amounts of which change following postsynthetic modifications. Using room-temperature isotopic exchange methods, it was determined that 17O was homogeneously incorporated into the zeolite framework, while 17O → 27Al polarization transfer experiments demonstrated that 17O incorporation does not occur for extra-framework AlnOm species. Data from samples exposed to controlled hydrolysis indicates that nearest neighbor Al pairs in the framework are more susceptible to hydrolytic attack. The data reported here suggest that Al(IV)-1/Al(IV)-2 paired sites are synergistic sites leading to increased reactivity in both low- and high-temperature reactions. No evidence was found for paired framework/nonframework sites.

Isotope and Spin Effects Induced by Compression of Paramagnetic Molecules

The zero-point energies (ZPEs) of paramagnetic molecules, free and compressed in a C59N paramagnetic cage, were computed. The excess of energy acquired by molecules under compression depended on the deuterium and tritium isotopes which ranged from 6–8 kcal/mol for H2+ to 1.0–1.5 kcal/mol for HO• and HO2. The differences in the ZPEs of compressed isotopic molecules resulted in large deuterium and tritium isotope effects which differed for singlet and triplet spin states. The hyperfine coupling (HFC) constants for protons and 17O nuclei decreased under compression, confirming the leakage of the unpaired π-electron from the central oxygen atom of guest molecules into the system of π-electrons of the cage, and its distribution over 60 atoms of the C59N. The latter seems to be the reason why the nitrogen-14 HFCs for C59N remain almost unchanged upon encapsulation of guest molecules. The singlet-triplet splitting is shown to depend on the Coulomb interaction, which controls the sign of the exchange potential. The importance of compression effects on the functioning of enzymes as molecular compressing devices is discussed.