Search NASA⌕ Search

SEARCH · Search NASA

Results for “spectrometers & spectroscopic techniques”

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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

Evolution of chirality from transverse wobbling in 135 Pr

Chirality is a distinct signature that characterizes triaxial shapes in nuclei. We report the first observation of chirality in the nucleus 135 Pr using a high-statistics Gammasphere experiment with the 123 Sb( 16 O, 4n) 135 Pr reaction. Two chiral-partner bands with the configuration π(1h11/2 )1 ⊗ ν(1h 11/2 ) −2 have been identified in this nucleus. Angular distribution analyses of the ΔI = 1 transitions connecting the two bands reveal a dominant dipole character, and quasiparticle triaxial rotor model calculations show good agreement with the data. Since the simultaneous observation of chirality and transverse wobbling in 135 Pr relies critically on these angular distribution results, we also address and refute the experimental and theoretical criticisms raised in a recent work by Lv et al., presenting additional evidence that further strengthens our interpretation. Furthermore, this marks the first observation of both hallmarks of triaxiality—chirality and wobbling—in the same nucleus.

90 ≤ A ≤ 149↗
DOE OSTI2025

Constraining the Synthesis of the Lightest 𝑝 Nucleus 74 Se

We provide the first experimental cross section of the 73 As(p, γ) 74 Se reaction to constrain one of the main destruction mechanisms of the p nucleus 74 Se in explosive stellar environments. The measurement was done using a radioactive 73 As beam at incident energies of 3.1 and 3.7 MeV/nucleon. Along with the total cross section measurement, statistical properties of the 74 Se compound nucleus were extracted, constraining the reaction cross section across the entire Gamow window of the γ process. The impact of the experimentally constrained reaction rate on 74 Se production in Type II supernovae is investigated through Monte Carlo one-zone network simulations. The results indicate that the overproduction of 74 Se by Type II supernova models cannot be resolved by nuclear physics and point towards the description of the astrophysical conditions of the γ process.

59 ≤ A ≤ 89↗
DOE OSTI2026

First observation of a high-𝐾 band structure in 162 Er and implications in the context of the identical bands phenomenon

The first ever identification of a high-𝐾 band structure in 162 Er is reported. Based on a 𝐾 𝜋 = 7 (−) isomer, it is found to be identical in nature to the corresponding 𝐾 𝜋 = 7 − sequence in 164 Er up to its highest observed spin. Furthermore, the phenomenon of identical high-K bands built on a two-quasiparticle configuration in an isotopic chain is reported here for the first time. While this is a notable addition to the systematics of known identical bands in nuclei at normal deformation, a satisfactory global understanding of the phenomenon remains elusive.

150 ≤ A ≤ 189↗
DOE OSTI2025

Deviations from the Porter-Thomas Distribution due to Nonstatistical 𝛾 Decay below the 150 Nd Neutron Separation Threshold

We introduce a new method for the study of fluctuations of partial transition widths based on nuclear resonance fluorescence experiments with quasimonochromatic linearly polarized photon beams below particle separation thresholds. It is based on the average branching of decays of 𝐽=1 states of an even-even nucleus to the 2$^{+}_{1}$ state in comparison to the ground state. Between 5 and 7 MeV, a constant average branching ratio for 𝛾 decays from 1 − states of 0.490(16) is observed for the nuclide 150 Nd. Assuming 𝜒 2 -distributed partial transition widths, this average branching ratio is related to a degree of freedom of 𝜈 = 1.93⁢(12), rejecting the validity of the Porter-Thomas distribution, requiring 𝜈 = 1. The observed deviation can be explained by nonstatistical effects in the 𝛾-decay behavior with contributions in the range of 9.4(10)% up to 94(10)%.

150 ≤ A ≤ 189↗
DOE OSTI2024

Detection of uranium-photofission neutrons with a 4 He scintillation detector

The use of photon active interrogation to detect special nuclear material has held significant theoretical promise, as the interrogating source particles, photons, are fundamentally different from one of the main signatures of special nuclear material: neutrons produced in nuclear fission. However, neutrons produced by photonuclear reactions in the accelerator target, collimator, and environment can obscure the fission neutron signal. These (γ, n) neutrons could be discriminated from fission neutrons by their energy spectrum, but common detectors sensitive to the neutron spectrum, like organic scintillators, are typically hampered by the intense photon background characteristic of photon-based active interrogation. In contrast, high-pressure 4 ⁢He-based scintillation detectors are well-suited to photon active interrogation, as they are similarly sensitive to fast neutrons and can measure their spectrum, but show little response to gamma rays. Here, in this work, a photon active interrogation system utilizing a 4 ⁢He scintillation detector and a 9 MeV linac-bremsstrahlung x-ray source was experimentally evaluated. The detector was shown to be capable of operating in intense gamma-ray environments and detecting photofission neutrons from 238 ⁢U when interrogated by this x-ray source. The photofission neutrons show clear spectral separation from (γ, n) neutrons produced in lead, a common shielding material.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2020

Evolution of collective and noncollective structures in 123 Xe

An experiment involving a heavy-ion-induced fusion-evaporation reaction was carried out where high-spin states of 123 Xe were populated in the 80 Se( 48 Ca,5n) 123 Xe reaction at 207 MeV beam energy. Gamma-ray coincidence events were recorded with the Gammasphere Ge detector array. The previously known level scheme was confirmed and enhanced with the addition of five new band structures and several interband transitions. Furthermore, cranked Nilsson-Strutinsky (CNS) calculations were performed and compared with the experimental results in order to assign configurations to the bands.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

Mass measurements of neutron-rich gallium isotopes refine production of nuclei of the first r -process abundance peak in neutron-star merger calculations

We report mass measurements of neutron-rich Ga isotopes 80–85 Ga with TRIUMF's Ion Trap for Atomic and Nuclear science. The measurements determine the masses of 80–83 Ga in good agreement with previous measurements. Here, the masses of 84 Ga and 85 Ga were measured for the first time. Uncertainties between 25 and 48 keV were reached. The new mass values reduce the nuclear uncertainties associated with the production of A ≈ 84 isotopes by the r-process for astrophysical conditions that might be consistent with a binary neutron star (BNS) merger producing a blue kilonova. Our nucleosynthesis simulations confirm that BNS merger may contribute to the first abundance peak under moderate neutron-rich conditions with electron fractions Y e = 0.35–0.38.

59 ≤ A ≤ 89↗
DOE OSTI2020

Reexamination of isoscalar giant resonances in 12 C and 93 Nb through 6 Li scattering

Inelastic Li 6 scattering at 100 MeV/u on C 12 and Nb 93 has been measured with the high-resolution magnetic spectrometer Grand Raiden. The magnetic-rigidity settings of the spectrometer covered excitation energies from 10 to 40 MeV and scattering angles in the range 0 ° < θ lab. < 2 ° . The isoscalar giant monopole resonance was selectively excited in the present data. Measurements free of instrumental background and the very favorable resonance-to-continuum ratio of Li 6 scattering allowed for precise determination of the E 0 strengths in C 12 and Nb 93 . Additionally, it was found that the monopole strength in C 12 exhausts 52 ± 3 (stat.) ± 8 (sys.) % of the energy-weighted sum rule (EWSR), which is considerably higher than results from previous α -scattering experiments. The monopole strength in Nb 93 exhausts 92 ± 4 (stat.) ± 10 (sys.) % of the EWSR, and it is consistent with measurements of nuclei with mass number of A ≈ 90 . Such comparison indicates that the isoscalar giant monopole resonance distributions in these nuclei are very similar, and no influence due to nuclear structure was observed.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

Prompt-delayed γ-ray spectroscopy of neutron-rich 119.121 In isotopes

The Z = 50 shell closure, near N = 82, is unique in the sense that it is the only shell closure with the spin-orbit partner orbitals, π g 9 / 2 and π g 7 / 2 , enclosing the magic gap. The interaction of the proton hole/particle in the above-mentioned orbitals with neutrons in the νh 11/2 orbital is an important prerequisite to the understanding of the nuclear structure near N = 82 and the νπ interaction. To explore the structural similarity between the high-spin isomeric states in In ( Z = 49), Sn ( Z = 50), and Sb ( Z = 51) isotopes from a microscopic point of view. In addition, to understand the role of a proton hole or particle in the spin-orbit partner orbitals, π g 9 / 2 and π g 7 / 2 , respectively, with neutron holes in the ν h 11 / 2 orbital on these aforementioned isomers. The fusion and transfer induced fission reaction Be 9 ( U 238 , f ) with 6.2 MeV/u beam energy, using a unique setup consisting of AGATA, VAMOS++, and EXOGAM detectors, was used to populate through the fission process and study the neutron-rich In 119 , 121 isotopes. This setup enabled the prompt-delayed γ -ray spectroscopy of isotopes in the time range of 100 ns – 200 μ s . In the odd- A In 119 , 121 isotopes, indications of a short half-life 19/2 - isomeric state, in addition to the previously known 25/2 + isomeric state, were observed from the present data. Further, new prompt transitions above the 25/2 + isomer in In 121 were identified along with reevaluation of its half-life. The experimental data were compared with the theoretical results obtained in the framework of large-scale shell-model calculations in a restricted model space. Furthermore, the ( π g 9 / 2 ν h 11 / 2 ; I | H ^ | π g 9 / 2 ν h 11 / 2 ; I ) two-body matrix elements of residual interaction were modified to explain the excitation energies and the B ( E 2) transition probabilities in the neutron-rich In isotopes. The (i) decreasing trend of E (29/2 + ) - E (25/2 + ) in odd-In (with dominant configuration π g 9 / 2 - 1 ν h 11 / 2 - 2 and maximum aligned spin of 29/2 + ) and (ii) increasing trend of E (27/2 + ) - E (23/2 + ) in odd-Sb (with dominant configuration π g 7 / 2 + 1 ν h 11 / 2 - 2 and maximum aligned spin of 27/2 + ) with increasing neutron number could be understood as a consequence of hole-hole and particle-hole interactions, respectively.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

Effect of an electric field on liquid helium scintillation produced by fast electrons

The dependence on applied electric field (0–40 kV/cm) of the scintillation light produced by fast electrons and α particles stopped in liquid helium in the temperature range of 0.44 K to 3.12 K is reported. For both types of particles, the reduction in the intensity of the scintillation signal due to the applied field exhibits an apparent temperature dependence. Using an approximate solution of the Debye-Smoluchowski equation, we show that the apparent temperature dependence for electrons can be explained by the time required for geminate pairs to recombine relative to the detector signal integration time. This finding indicates that the spatial distribution of secondary electrons with respect to their geminate partners possesses a heavy, non-Gaussian tail at larger separations and has a dependence on the energy of the primary ionization electron. Here, we discuss the potential application of this result to pulse shape analysis for particle detection and discrimination.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

Search for the 1/2 + intruder state in 35 P

The excitation energy of deformed intruder states (specifically the 2p2h bandhead) as a function of proton number Z along N = 20 is of interest both in terms of better understanding the evolution of nuclear structure between spherical Ca 40 and the Island of Inversion nuclei, and for benchmarking theoretical descriptions in this region. At the center of the N = 20 Island of Inversion, the n p n h (where n = 2 , 4 , 6 ) neutron excitations across a diminished N = 20 gap result in deformed and collective ground states, as observed in Mg 32 . In heavier isotones, n p n h excitations do not dominate in the ground states but are present in the relatively low-lying level schemes. With the aim of identifying the expected 2 p 2 h x s 1 / 2 + state in P 35 , the only N = 20 isotone for which the neutron 2p2h excitation bandhead has not yet been identified, the S 36 ( d , He 3 ) P 35 reaction has been revisited in inverse kinematics with the HELical Orbit Spectrometer (HELIOS) at the Argonne Tandem Linac Accelerator System (ATLAS). While a candidate state has not been located, an upper limit for the transfer reaction cross section to populate such a configuration within a 2.5 to 3.6 MeV energy range provides a stringent constraint on the wave function compositions in both S 36 and P 35 .

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

Evolution of collectivity in 118 Xe

A recoil-distance Doppler shift experiment has been performed using the Pd 102 ( F 19 , p 2 n ) reaction at a beam energy of 73 MeV to measure the lifetime of excited states in Xe 118 . Additionally, the differential decay-curve method using γ γ coincidences and a gating procedure that allows to extract the lifetime without feeding assumptions has been employed. The lifetimes obtained for the yrast states up to spin-parity 8 + are compared with interacting boson model calculations and Xe 118 can be classified as a transitional nucleus between the spherical and a deformed shape. Systematics of the B ( E 2 ) values for the 2 + → 0 + and 4 + → 2 + transitions in the isotopic chains of tin, tellurium and xenon are presented. It is proposed that a “critical point” exists at which the B ( E 2 ; 4 + → 2 + ) / B ( E 2 ; 2 + → 0 + ) ratio drops to unity for lower neutron numbers within the isotopic chain. The position of the “critical point” varies with proton number, i.e., it is presumed to be located at the same mass number A = 114 in the Sn, Te, and Xe isotopes.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2021

Highly deformed band structures due to core excitations in 123 Xe

High-spin states in 123 Xe were populated in the 80 Se( 48 Ca, 5n) 123 Xe reaction at a beam energy of 207 MeV. γ-ray coincidence events were recorded with the Gammasphere spectrometer. Four new high-spin bands have been discovered in this nucleus. The bands are compared with those calculated within the framework of cranked Nilsson-Strutinsky and cranked Nilsson-Strutinsky-Bogoliubov models. Furthermore, it is concluded that the configurations of the bands involve two-proton excitations across the Z = 50 as well as excitation of neutrons across the N = 82 shell gaps resulting in a large deformation, ε 2 ≈ 0.30 and γ ≈ 5°.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2021

Mass measurements of neutron-rich indium isotopes for r -process studies

A new series of neutron-rich indium mass measurements is reported from the TITAN multiple-reflection time-of-flight mass spectrometer (MR-TOF-MS). These mass measurements cover 125-134 In (N = 76–85) and include ground states as well as isomeric states. The masses of nuclei in this region are known to be of great importance for accurately modeling r-process nucleosynthesis, and the significance of the reported neutron-rich indium masses is discussed in this context. Results are compared with earlier experimental data where available as well as theoretical mass models. The measurements reported here include the first mass measurements of 133,134 In, as well as the first direct mass measurement of 132 In. The masses of 125-131 In ground states and several isomers were previously measured to higher precision by Penning trap mass spectrometry, which also resolved some low-lying isomers that could not be resolved in this work. The earlier Penning trap measurements serve as excellent cross-checks for the MR-TOF-MS measurements, and in some cases the MR-TOF-MS measurements improve the literature uncertainties of higher-lying isomer masses and excitation energies. Finally, a new isomeric state for 128 In, recently reported for the first time by the JYFLTRAP group, is also confirmed by the TITAN MR-TOF-MS, with a measured excitation energy of 1813(17) keV.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2021

Pseudospin-doublet bands and Gallagher Moszkowski doublet bands in 100 Y

New transitions in neutron-rich 100 Y have been identified in a 9 Be + 238 U experiment with mass and Z gates to provide full fragment identification. These transitions and high spin levels of 100 Y have been investigated by analyzing the high statistics γ–γ–γ and γ–γ–γ–γ coincidence data from the spontaneous fission of 252 Cf at the Gammasphere detector array. Two new bands, 14 new levels, and 23 new transitions have been identified. The K π = 4 + new band decaying to a 1s isomeric state is assigned to be the high-K Gallagher-Moszkowski (GM) partner of the known K π = 1 + band, with the π5/2[522]Ⓧν3/2[411] configuration. This 4 + band is also proposed to be the pseudospin partner of the new K π = 5 + band with a 5 + π5/2[422] Ⓧ ν5/2[413] configuration, to form a π5/2[422] Ⓧ ν[3125/2,3/2] neutron pseudospin doublet. Here, constrained triaxial covariant density-functional theory and quantal particle rotor model calculations have been applied to interpret the band structure and available electromagnetic transition probabilities and are found to be in good agreement with experimental values.

100Y↗
DOE OSTI2021

Level structure of the T z = –1 nucleus 34 Ar and its relevance for nucleosynthesis in ONe novae

The 24 Mg+ 12 C fusion reaction was used to perform a detailed γ-ray spectroscopy study of the astrophysically important nucleus 34 Ar. In particular, an experimental setup, coupling the advanced γ-ray tracking array GRETINA with the well-established Argonne fragment mass analyzer (FMA), was employed to obtain excitation energies and spin-parity assignments for excited states in 34 Ar, both above and below the proton separation energy. For the first time, an angular distribution analysis of in-beam γ rays from fusion-evaporation reactions, using a tracking array, has been performed and Coulomb energy differences of analog states in the T = 1, A = 34 mirror system, explored from 0 to 6 MeV. Lastly, we present a comprehensive discussion of the astrophysical 33 Cl(p,γ) stellar reaction rate, together with implications for the identification of nova presolar grains from sulfur isotopic abundances.

20 ≤ A ≤ 38↗
DOE OSTI2021

Potential neutron-induced γ-ray background on natural tellurium relevant to 130 Te 0 ν ββ decay searches at the CUORE and SNO+ detectors

Gamma-ray production cross-section data have been obtained for the inelastic neutron scattering reactions 126,128,130 Te(n,n'γ) at five neutron energies between 3.6 and 10 MeV. We report data for the γ-ray energy region relevant to 0ν ββ decay of 130 Te with a Q ββ value of 2527.515 keV, assuming natural-abundance tellurium, as used at CUORE and SNO+. The natural abundance of 130 Te, 128 Te, and 126 Te is 34%, 32%, and 19%, respectively. For CUORE the γ-ray cascades from the excited state in 130 Te at 2527.06 keV and in 126 Te at 2533.85 keV are of concern. For SNO+, accounting for its inferior energy resolution, an additional four levels are important in 130 Te, an additional nine levels in 128 Te, and an additional eight levels in 126 Te. Of these, we report neutron-induced γ-ray production cross sections for the strongest transitions: the 2581.15 keV level in 130 Te, the 2494.20, 2508.06, and 2630.14 keV levels in 128 Te, and the 2496.83 and 2585.46 keV level in 126 Te. Here, the largest cross-section values were found for cascade γ-ray transitions to the ground state, while direct transitions to the ground state are very weak and were not observed in the present work. Both the CUORE and SNO+ detectors, however, may not be able to distinguish between cascade transitions and direct transitions to the ground state, making the neutron-induced excitation of the 2527.06 keV state of 130 Te in particular a potential problem for 0νββ decay searches of 130Te, because it matches its Q ββ value.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2021

Exploring the role of high- j configurations in collective observables through the Coulomb excitation of 106 Cd

In this work, the shape and collectivity of 106 Cd was investigated via a sub-barrier-energy Coulomb excitation experiment performed at the NSCL ReA3 facility using the JANUS setup. Transition matrix elements between low-lying states were found to agree with adopted values, and information on the shape and collectivity of higher-lying states was extracted for the first time. Locally-optimized large-scale shell-model calculations were found to describe well the B(E2) transition strengths but failed to reproduce the spectroscopic quadrupole moments Q s . An analysis of the E2 rotational invariants and the normalized quadrupole moment q s indicates that this may be due to a significant degree of triaxiality in 106 Cd which is not captured by the present shell-model calculations. Analogous calculations for the Fe isotopes (two protons below the Z = 28 magic number) reveal the critical role of high-j neutron configurations for the description of quadrupole moments in the heavy Fe and Cd isotopes (two protons below magic Z = 50), but this effect is insufficient to explain the shape of 106 Cd, posing a puzzle for the understanding of nuclear structure towards N = 50.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗