Search NASA⌕ Search

SEARCH · Search NASA

Results for “Proton emission”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Effects of triaxiality and residual n p interaction in the proton emission from Ho 140

Here we present a detailed theoretical investigation of proton emission from 140 Ho within the nonadiabatic quasiparticle approach. The calculated proton emission half-life reproduces well the measured data. The importance of triaxiality and of the residual np interaction are studied. The ground state spin and parity of 139 Dy (daughter) and 140 Ho (parent) are ascertained unambiguously as 7/2 + and 3 – , respectively, by analyzing the rotational energies, half-lives, and branching ratios.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2025

Proton emission in ultraperipheral Pb-Pb collisions at $\sqrt{𝑠_{𝑁⁢𝑁}}$ = 5.02 TeV

The first measurements of proton emission accompanied by neutron emission in the electromagnetic dissociation (EMD) of 208 Pb nuclei in the ALICE experiment at the Large Hadron Collider are presented. The EMD protons and neutrons emitted at very forward rapidities are detected by the proton and neutron zero degree calorimeters of the ALICE experiment. The emission cross sections of zero, one, two, and three protons accompanied by at least one neutron were measured in ultraperipheral 208 Pb − 208 Pb collisions at a center-of-mass energy per nucleon pair $\sqrt{𝑠_{𝑁⁢𝑁}}$ = 5.02TeV. The 0p and 3p cross sections are described by the RELDIS model within their measurement uncertainties, while the 1p and 2p cross sections are underestimated by the model by 17–25%. According to this model, these 0p, 1p, 2p, and 3p cross sections are associated, respectively, with the production of various isotopes of Pb, Tl, Hg, and Au in the EMD of 208 Pb . The cross sections of the emission of a single proton accompanied by the emission of one, two, or three neutrons in EMD were also measured. The data are significantly overestimated by the RELDIS model, which predicts that the (1p,1n), (1p,2n), and (1p,3n) cross sections are very similar to the cross sections for the production of the thallium isotopes 206,205,204 Tl.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

57 Zn β-delayed proton emission establishes the 56 Ni rp-process waiting point bypass

We measured the 57 Zn β-delayed proton (βp) and γemission at the National Superconducting Cyclotron Laboratory. We find a 57 Zn half-life of 43.6 ± 0.2ms, βp branching ratio of (84.7 ±1.4)%, and identify four transitions corresponding to the exotic β-γ-pdecay mode, the second such identification in the fp-shell. The p/γratio was used to correct for isospin mixing while determining the 57 Zn mass via the isobaric multiplet mass equation. Previously, it was uncertain as to whether the rp-process flow could bypass the textbook waiting point 56 Ni for astrophysical conditions relevant to Type-I X-ray bursts. Our results definitively establish the existence of the 56 Ni bypass, with 14-17% of the rp-process flow taking this route.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Identification of Prompt Proton Emission in $N = Z - 1$ 61 Ga: Isospin Symmetry at the Limit of Nuclear Binding

Excited states in the proton drip line nucleus 61 Ga were populated via the fusion-evaporation reaction 24 Mg ⁢( 40 Ca, 𝑝⁢2⁢𝑛)⁢ 61 Ga. The experimental setup at Argonne National Laboratory comprised a novel combination of the Gammasphere array with two CD-shaped double-sided Si-strip detectors inside the Microball CsI(Tl) charged-particle detection array, as well as the Neutron-Shell liquid scintillators and the Fragment Mass Analyzer. Owing to the setup’s unprecedented in-beam proton spectroscopy and tracking capabilities, a coincidence between a 957.6(5)-keV 𝛾 ray and a 1.876(24)-MeV proton line was observed, which identifies the quasibound proton 𝜋⁢𝑔 9/2 single-particle state in 61 Ga at 𝐸 𝑥 = 2150⁢(34) keV. This probes isospin symmetry at the limit of nuclear binding by providing a unique challenge for the shell-model interpretation of mirror nuclei beyond doubly magic 56 Ni .

Hrabar, Yuliia [Lund Univ. (Sweden)] (ORCID:000000↗
DOE OSTI2022

β -delayed charged-particle decay of Si 22 , 23

The β decay of 22,23 Si by emission of delayed charged particles was investigated in an experiment at the Cyclotron Institute of Texas A&M University by means of an optical-readout time-projection chamber. The previously-known decay of the two isotopes by β-delayed one- and two-proton emission was confirmed. Here for the first time, a new, rare, decay mode for 23 Si, β-delayed three-proton emission, was observed and β-delayed proton-α emission tentatively identified. Moreover, the β-decay pattern for the ground state of 23 Si was studied by means of multireference density-functional-rooted calculations.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2025

Alpha-decay width of a near proton-threshold resonance in the 7 Li( α, α ) channel

We investigate the alpha-decay width of a near proton-threshold resonance in 11 B by the excitation functions of 7 Li(α, α) and 7 Li(α, α’) reactions. This resonance is an example of loosely bound atomic nuclei, understood as small open quantum systems, that exhibit properties significantly influenced by their coupling to the continuum. The present experiment focuses on the formation of a specific state in 11 B at excitation energy in the region near 11.4 MeV by bombarding a 7 Li target with a 4 He beam at energies ranging from 3.92 to 4.56 MeV in the laboratory frame. The study provides data complementary to previous observations of the proton emission in the β-decay of the neutron-rich halo nucleus 11 Be. An R-matrix fit to the data provides resonance energy and partial widths consistent with J π =1/2 + for a narrow near-threshold state in 11 B at 11.400(20) MeV, that is 171(20) keV above the proton emission threshold, with partial α-decay width Γ α =2.5$^{+3.5}_{–1.5}$ keV in elastic scattering and Γ α' =15.8$^{+1.9}_{–0.4}$ keV in inelastic scattering. These findings contribute to the understanding of the structure of this open quantum system resonance.

11B↗
DOE OSTI2022

Proton decay spectroscopy of S 28 and Cl 30

States in 28 S and 30 Cl have been studied using one- and two-proton decay spectroscopy. In the first spectrometer setting, states in 28 S were populated following one-neutron knockout from a fast 29 S beam. Three new states are observed in 28 S from one- and two-proton decay. For the two-proton case the nature of the decay was investigated and found to proceed via sequential two-proton emission. For the second setting, states in 30 Cl were populated via one-proton knockout from a fast 31 Ar beam. The decay energy of the ground and first excited state were measured, with the ground-state decay energy found to be in disagreement with a previous measurement. Here, the spin and parity of these two 30 Cl states were inferred from shell-model calculations.

20 ≤ A ≤ 38↗
DOE OSTI2022

β - p and β - α decay of the 11 Be neutron halo ground state

Beta-delayed proton emission from the neutron halo ground state of 11 Be raised much attention due to the unusually high decay rate. It was argued that this may be due to the existence of a resonance just above the proton decay threshold. In this letter, we use the lenses of real-energy continuum shell model to describe several observables including the Gamow–Teller rates for the β - -delayed α and proton decays, and argue that, within our model, the large β - p branching ratio cannot be reconciled with other data.

11Be↗
DOE OSTI2022

Fine structure in the odd-odd proton emitter Tm 144

Axial symmetry breaking in 144 Tm is probed by examining its proton emission fine structure. The ground-state spin and parity in 144 Tm and daughter 143 Er are assigned unambiguously based on the corroboration of our calculations with the present data. Here we establish the first microscopic description of fine structure in odd-odd proton emitters, which is capable of resolving ambiguities present in the assignments of transitions in such nuclei.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2023

Description of the Proton-Decaying 0 2 + Resonance of the α Particle

The recent precise experimental determination of the monopole transition form factor from the ground state of 4 He to its $0$$^{+}_{2}$ resonance via electron scattering has reinvigorated discussions about the nature of this first excited state of the α particle. The $0$$^{+}_{2}$ state has been traditionally interpreted in the literature as the isoscalar monopole resonance (breathing mode) or, alternatively, as a particle-hole shell-model excitation. To better understand the nature of this state, which lies only ~410 keV above the proton emission threshold, we employ the coupled-channel representation of the no-core Gamow shell model. By considering the [ 3 H + p], [ 3 He + n], and [ 2 H + 2 H] reaction channels, we explain the excitation energy and monopole form factor of the $0$$^{+}_{2}$ state. Furthermore, we argue that the continuum coupling strongly impacts the nature of this state, which carries characteristics of the proton decay threshold.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

Establishing the ground-state spin of 71 Kr

Nuclei in the vicinity of the N=Z line provide many sensitive probes of isospin symmetry. One example concerns the character and sequence of low-lying states of the T=1/2 mirror pair 71 Kr and 71 Br which has been under debate for several decades. In this paper we report a new measurement of the absolute β-branching to ground and excited states which, taken with our precise lifetime of T 1/2 =94.9(4) ms , gives a superallowed ground state–to–ground state log (ft) value of 3.64(4). This is only consistent with both 71 Br and 71 Kr having the same spin and parity, J π =5/2 – , as expected from mirror symmetry. The β-delayed proton emission to the first-excited state in 70 Se was observed for the first time which also strongly supports this assignment.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

Shell-model studies of the astrophysical r p -process reactions S 34 ( p , γ ) Cl 35 and Cl 34 g , m ( p , γ ) Ar 35

Background: Dust grains condensed in the outflows of presolar classical novae should have been present in the protosolar nebula. Candidates for such presolar nova grains have been found in primitive meteorites and can in principle be identified by their isotopic ratios, but the ratios predicted by state-of-the-art one-dimensional hydrodynamic models are uncertain due to nuclear-physics uncertainties. Purpose: To theoretically calculate the thermonuclear rates and uncertainties of the S 34 ( p , γ ) Cl 35 and Cl 34 g , m ( p , γ ) Ar 35 reactions and investigate their impacts on the predicted 34 S/ 32 S isotopic ratio for presolar nova grains. Method: A shell-model approach in a (0 +1 ) ℏ ω model space was used to calculate the properties of resonances in the 34 S(p ,γ ) 35 Cl and 34 g,m Cl (p ,γ ) 35 Ar reactions and their thermonuclear rates. Uncertainties were estimated using a Monte Carlo method. The implications of these rates and their uncertainties on sulfur isotopic nova yields were investigated using a postprocessing nucleosynthesis code. The rates for transitions from the ground state of 34 Cl as well as from the isomeric first excited state of 34 Cl were explicitly calculated. Results: At energies in the resonance region near the proton-emission threshold, many negative-parity states appear. Energies, spectroscopic factors, and proton-decay widths are reported. The resulting thermonuclear rates are compared with previous determinations. Conclusions: The shell-model calculations alone are sufficient to constrain the variation of the 34 S/ 32 S ratios to within about 30%. Uncertainties associated with other reactions must also be considered, but in general we find that the 34 S/ 32 S ratios are not a robust diagnostic to clearly identify presolar grains made from nova ejecta.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2021

Observation of the Exotic Isotope 13 F Located Four Neutrons beyond the Proton Drip Line

A 13 F resonance was observed following a charge-exchange reaction between a fast 13 O beam and a 9 Be target. The resonance was found in the invariant-mass distribution of 3p+ 10 C events and probably corresponds to a 5/2 + excited state. The ground state was also expected to be populated, but was not resolved from the background. The observed level decays via initial proton emissions to both the ground and first 2 + state of 12 O, which subsequently undergo 2p decay. In addition there may also be a significant proton decay branch to the second 2+ level in 12 O. The wavefunction associated with the observed level may be collectivized due to coupling to the continuum as is it located just above the threshold for proton decay to the second $2^{+}_{2}$ state of 12 O.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2021

25 Siβ + -decay spectroscopy

Background: β-decay spectroscopy provides valuable information on exotic nuclei and a stringent test for nuclear theories beyond the stability line. Purpose: To search for new β-delayed protons and γ rays of 25 Si to investigate the properties of 25 Al excited states. Method: 25 Si β decays were measured by using the Gaseous Detector with Germanium Tagging system at the National Superconducting Cyclotron Laboratory. The protons and γ rays emitted in the decay were detected simultaneously. Here, a Monte Carlo method was used to model the Doppler broadening of 24 Mg γ-ray lines caused by nuclear recoil from proton emission. Shell-model calculations using two newly developed universal sd-shell Hamiltonians were performed. Results: The most precise 25Si half-life to date has been determined. A new proton branch at 724(4) keV and new proton-γ-ray coincidences have been identified. Three 24 Mg γ-ray lines and eight 25 Al γ-ray lines are observed for the first time in 25 Si decay. The first measurement of the 25 Si β-delayed γ-ray intensities through the 25 Al unbound states is reported. All the bound states of 25 Al are observed to be populated in the β decay of 25 Si. Several inconsistencies between the previous measurements have been resolved, and new information on the 25 Al level scheme is provided. An enhanced decay scheme has been constructed and compared to the mirror decay of 25 Na and the shell-model calculations. Conclusions: The measured excitation energies, γ-ray and proton branchings, log $ft$ values, and Gamow-Teller transition strengths for the states of 25 Al populated in the β decay of 25 Si are in good agreement with the shell model calculations, offering gratifyingly consistent insights into the fine nuclear structure of 25 Al.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2026

FLASH-therapy suitable single-pulse proton generation using TiH 2 under nanosecond laser irradiation

We investigated proton emission from titanium hydride (TiH 2 ) targets irradiated in vacuum by a 6-ns, 1064-nm Nd:YAG laser. Time-of-flight measurements with a Faraday cup and an electrostatic ion analyzer resolved distinct proton peaks at high pulse energies, with yields on the order of 10 9 protons per shot. Systematic scans over pulse energy and up to 1000 repeated shots showed that, while the peak amplitude gradually decreased, the integrated proton number remained nearly constant. This behavior is consistent with surface-induced broadening of the plasma expansion while bulk hydrogen is replenished by diffusion and repeated ablation of fresh TiH 2 layers. Using the measured proton numbers and pulse widths, a simple direct-plasma-injection-style scaling indicates peak currents of ∼100 mA and sub-microsecond pulse durations. The pulse structure and yield satisfy key ultra-high-dose-rate criteria and, together with sustained output over 1000 shots, support TiH 2 -based laser ion sources as practical candidates for FLASH-therapy (ultra-high-dose-rate)-oriented studies and injector development using direct plasma injection.

43 PARTICLE ACCELERATORS↗
DOE OSTI2021

Proton decays in 16 Ne and 18 Mg and isospin-symmetry breaking in carbon isotopes and isotones

We report that proton-rich nuclei possess unique properties in the nuclear chart. Due to the presence of both continuum coupling and Coulomb interaction, phenomena such as halos, Thomas-Ehrman shift, and proton emissions can occur. Relevant experimental data are difficult to obtain, so that theoretical calculations are needed to understand nuclei at drip lines and to guide experimentalists. In particular, the 16 Ne and 18 Mg isotopes are supposed to be one-proton and/or two-proton emitting nuclei, but associated experimental data are either incomplete or even unavailable. Consequently, we performed Gamow shell model calculations of carbon isotones bearing A = 15 - 18 . Isospin-symmetry breaking occurring in carbon isotones and isotopes is also discussed. It is hereby shown that the mixed effects of continuum coupling and Coulomb interaction at drip lines generate complex patterns in isospin multiplets. Added to that, it is possible to determine the one-proton and two-proton widths of 16 Ne and 18 Mg . Obtained decay patterns are in agreement with those obtained in previous experimental and theoretical works. Moreover, to our knowledge, this is the first theoretical calculation of binding energy and partial decay widths of 18 Mg in a configuration interaction picture.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗