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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2013

Electromagnetic properties of the 2+ state in 134Te: Influence of core excitation on single-particle orbits beyond 132Sn

The g factor and B (E2) of the first excited 2+ state have been measured following Coulomb excitation ofthe neutron-rich semimagic nuclide 134Te (two protons outside 132Sn) produced as a radioactive beam. The precision achieved matches related g-factor measurements on stable beams and distinguishes between alternative models. The B(E2) measurement exposes quadrupole strength in the 2+ state beyond that predicted by current large-basis shell-model calculations. This additional quadrupole strength can be attributed to coupling between the two valence protons and excitations of the 132Sn core. However, the wave functions of the low-excitation positive-parity states in 134Te up to 6+ remain dominated by the (g7/2)2 configuration.

Stuchbery, Andrew E↗
NASA NTRS1973

Proton collisional excitation in the ground configuration of Fe/+12/.

Using semiclassical Coulomb excitation theory, proton collisional excitation and deexcitation cross sections are calculated for all transitions between the Fe(+12) ground configuration levels. Rate constants pertaining to these processes are then derived for coronal temperatures. These rates are shown to be comparable in all cases to the corresponding electron rate constants.

Landman, D. A.↗
DOE OSTI2016

Studies of the shapes of heavy pear-shaped nuclei at ISOLDE

For certain combinations of protons and neutrons there is a theoretical expectation that the shape of nuclei can assume octupole deformation, which would give rise to reflection asymmetry or a ”pear-shape” in the intrinsic frame, either dynamically (octupole vibrations) or statically (permanent octupole deformation). I will briefly review the historic evidence for reflection asymmetry in nuclei and describe how recent experiments carried out at REX-ISOLDE have constrained nuclear theory and how they contribute to tests of extensions of the Standard Model. I will also discuss future prospects for measuring nuclear shapes from Coulomb Excitation: experiments are being planned that will exploit beams from HIE-ISOLDE that are cooled in the TSR storage ring and injected into a solenoidal spectrometer similar to the HELIOS device developed at the Argonne National Laboratory.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2016

On the equivalence of experimental B(E2) values determined by various techniques

In this paper, we establish the equivalence of the various techniques for measuring B(E2) values using a statistical analysis. Data used in this work come from the recent compilation by B. Pritychenko et al. (2016). We consider only those nuclei for which the B(E2) values were measured by at least two different methods, with each method being independently performed at least twice. Our results indicate that most prevalent methods of measuring B(E2) values are equivalent, with some weak evidence that Doppler-shift attenuation method (DSAM) measurements may differ from Coulomb excitation (CE) and nuclear resonance fluorescence (NRF) measurements. However, such an evidence appears to arise from discrepant DSAM measurements of the lifetimes for 60 Ni and some Sn nuclei rather than a systematic deviation in the method itself.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2015

Nuclear Data Sheets for A = 224

The experimental nuclear spectroscopic data for ten experimentally known nuclides of mass number 224 (Bi, Po, At, Rn, Fr, Ra, Ac, Th, Pa, U) have been evaluated and presented together with the Adopted properties for levels and γ rays. For {sup 224}Bi, {sup 224}Po, {sup 224}At, {sup 224}Rn, {sup 224}Fr, {sup 224}Pa and {sup 224}U nuclei, only the ground–state information is known. Half–lives of ground states of 224Bi and 224Po have not yet been measured. The decay of {sup 224}Rn to {sup 224}Fr has been studied, but no decay scheme has been proposed. The decay of {sup 224}Ac to {sup 224}Ra is reported only in an abstract style conference proceedings. For a definite Jπ assignment for ground state of {sup 224}Ac, a detailed study of this decay may be helpful. In the decay of {sup 228}Pa to {sup 224}Ac, authors of 1994Ah03 state that the lowest state observed in their work may not be the ground state. Thus an extensive study of {sup 228}Pa α decay, and studies involving nuclear reactions are warranted since the level scheme of {sup 224}Ac presented in this evaluation is considered as incomplete due to the lack of confirmed information about multipolarities, mixing ratios and other spectroscopic details. Three new nuclides {sup 224}Bi, {sup 224}Po, and {sup 224}At are added in this revision, together with new in–beam γ–ray and Coulomb excitation data for {sup 224}Ra. Although, not much new experimental data have appeared since the previous evaluation (1997Ar05), extensive modifications have been made in almost all the datasets. This work supersedes the information presented in the previous NDS evaluations of A = 224: 1997Ar05, 1986Ma45 and 1976El05.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2011

Study of near-stability nuclei populated as fission fragments in heavy-ion fusion reactions

Examples are presented to illustrate the power of prompt {gamma}-ray spectroscopy of fission fragments from compound nuclei with A{approx}200 formed in fusion-evaporation reactions in experiments using the Gammasphere Ge-detector array. Complementary methods, such as Coulomb excitation and deep-inelastic processes, are also discussed. In other cases (n,xn{gamma}) reactions on stable isotopes have been used to establish neutron excitation functions for {gamma}-rays using a pulsed 'white'-neutron source, coupled to a high-energy-resolution germanium-detector array. The excitation functions can unambiguously assign {gamma}-rays to a specific reaction product. Results from all these methods bridge the gaps in the systematics of high-spin states between the neutron-deficient and neutron-rich nuclei. Results near shell closures should motivate new shell model calculations.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2014

Nuclear Data Sheets for A = 54

The 2005 evaluation for A=54 (2006Hu08) has been updated. Detailed experimental nuclear structure data and decay data for all nuclei with mass chain A=54 are presented in this current evaluation. The new data and information are given in following datasets: {sup 54}Ca: {sup 9}Be({sup 76}Ge, X) and Be({sup 55}Sc, p), ({sup 56}Ti, 2p) {sup 54}Sc: {sup 54}Ca β{sup −} decay and {sup 54}Sc IT decay {sup 54}Ti: {sup 54}Sc β{sup −} decay {sup 54}Cr: {sup 54}Mn ε decay, {sup 56}Fe(μ, nupng), and {sup 238}U({sup 64}Ni, Xγ) {sup 54}Mn: {sup 51}V({sup 20}Ne, Xγ), {sup 55}Mn(p, pn), and {sup 56}Fe(μ, nu2ng) {sup 54}Fe: {sup 58}Ni α decay, {sup 9}Be({sup 55}Co, Xγ), {sup 54}Fe(e, e'), {sup 54}Fe(p, p'), and Coulomb Excitation {sup 54}Co: {sup 54}Ni ε decay, {sup 55}Cu εp decay, {sup 28}Si({sup 32}S, αpnγ), {sup 54}Fe(p,n), and {sup 54}Fe({sup 3}He, t) {sup 54}Ni: {sup 54}Ni IT decay, {sup 55}Zn εp decay, {sup 9}Be({sup 55}Ni, Xγ), and {sup 24}Mg({sup 32}S, Xγ) {sup 54}Zn: Ni({sup 58}Ni, X)

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2024

Suppressed electric quadrupole collectivity in Si 32

Lying between O 16 and Ca 40 , the s d shell is well described by robust phenomenological and nuclear theories. In this work, however, we highlight an unexplained reduction in electric-quadrupole strength in the rare isotope Si 32 , studied through sub-barrier Coulomb excitation. It is found that the oblate nature of the deformation is well reproduced, while the absolute scale of quadrupole deformation, however, is inhibited by approximately a factor of 2 compared to theoretical predictions. Through comparison with shell-model and calculations, we present a number of possible explanations for this inhibited E 2 strength. By comparing the results of these calculations to multiple observables, we conclude that there is a reduced role for out-of-space excitations in Si 32 , resulting in a reduction in the corrections normally applied to both models. Published by the American Physical Society 2024

20 ≤ A ≤ 38↗
DOE OSTI2014

Pygmy dipole resonance and dipole polarizability in {sup 90}Zr

Electric dipole (E1) reduced transition probability B(E1) of {sup 90}Zr was obtained by the inelastic proton scattering near 0 degrees using a 295 MeV proton beam and multipole decomposition analysis of the angular distribution by the distorted-wave Born approximation with the Hartree-Fock plus random-phase approximation model and inclusion of El Coulomb excitation, and the E1 strength of the pygmy dipole resonance was found in the vicinity of the neutron threshold in the low-energy tail of the giant dipole resonance. Using the data, we plan to determine the precise dipole polarizability α{sub D} which is defined as an inversely energy-weighted sum value of the elecrric dipole strength. The dipole polarizability is expected to constrain the symmetry energy term of the neutron matter equation of state. Thus systematical measurement of the dipole polarizability is important.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2012

Transient field g factor and mean-life measurements with a rare isotope beam of 126Sn

Background: The g factors and lifetimes of the 2+1 states in the stable, proton-rich Sn isotopes have been measured, but there is scant information on neutron-rich Sn isotopes. Purpose: Measurement of the g factor and the lifetime of the 2+1 state at 1.141 MeV in neutron-rich 126Sn (T1/2 = 2.3 105y). Method: Coulomb excitation in inverse kinematics together with the transient field and the Doppler shift attenuation techniques were applied to a radioactive beam of 126Sn at the Holifield Radioactive Ion Beam Facility. Results: g(2+1 ) = 0.25(21) and (2+1 ) = 1.5(2) ps were obtained. Conclusions: The data are compared to large-scale shell-model and quasiparticle random-phase calculations. Neutrons in the h11/2 and d3/2 orbitals play an important role in the structure of the 2+1 state of 126Sn. Challenges, limitations, and implications for such experiments at future rare isotope beam facilities are discussed.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Direct Measurement of Octupole Deformation in 146 Ba

The octupole strength present in the neutron-rich, radioactive nucleus 146 Ba has been experimentally determined for the first time using Coulomb excitation. To achieve this, A=146 fission fragments from CARIBU were post-accelerated by the Argonne Tandem Linac Accelerator System (ATLAS) and impinged on a thin 208 Pb target. Using the GRETINA gamma-ray spectrometer and the CHICO2 heavy-ion counter, the reduced transition probability B(E3; 3- ->0 + ) was determined as 48(+21/-29) W.u. The new result provides further experimental evidence for the presence of a region of octupole deformation surrounding the neutron-rich barium isotopes.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2025

Triaxiality and shape dynamics in 70 Ge

The electromagnetic properties of low-lying states in 70 Ge were investigated via multi-step Coulomb excitation of a 70 Ge beam impinging on a 208 Pb target at the ATLAS facility of the Argonne National Laboratory. A total of 27 transitional elements and six diagonal matrix elements coupling 11 low-lying states, were extracted from the measured cross sections. These were used to calculate reduced transition probabilities, spectroscopic quadrupole moments, and rotational invariant shape parameters, providing enhanced precision and expanding on previous studies. The experimental data were compared within several theoretical frameworks, including the generalized triaxial rotor model, configuration interaction shell-model calculations, and computations within the combined frameworks of relativistic density functional theory and the five-dimensional collective Hamiltonian. The results demonstrate a good agreement with the experimental data and, in conjunction with calculations using a two-state mixing model, support significant triaxiality and strong mixing between the 0$^{+}_{1}$ and 0$^{+}_{2}$ states. This results in the magnitudes of their respective quadrupole deformations [β rms (0$^{+}_{1}$) = 0.228 (3), β rms (0$^{+}_{2}$) = 0.273 (1)] being more similar than previously observed. Furthermore, the implications of these results for understanding the complex shape coexistence phenomena, the role of triaxiality, and shape evolution along the Ge isotopic chain are discussed.

59 ≤ A ≤ 89↗
DOE OSTI2023

Triaxiality and the nature of low-energy excitations in Ge 76

The deformation properties of the low-lying states in 76 Ge have been investigated following a safe energy Coulomb excitation measurement with the GRETINA tracking array and CHICO2 heavy-ion counter at the ATLAS accelerator facility at Argonne National Laboratory. A comprehensive set of transition and static E2 matrix elements were extracted from the measured differential Coulomb cross-sections, and compared with results of configuration interaction shell-model calculations and computations carried out within the framework of the generalized triaxial rotor model. The remarkable agreement between the calculated and experimental data supports a near-maximum triaxial deformation for the ground state of 76 Ge. Additionally, the degree of softness of the asymmetry in 76 Ge and 76 Se was investigated using rotational invariants generated from configuration interaction shell-model wave functions computed with the jj44b and JUN45 effective interactions. The resulting invariants are shown to be consistent with a stiff triaxial deformation in 76 Ge and a predominantly soft triaxial potential for 76 Se, in agreement with the conclusions of recent works by this collaboration.

59 ≤ A ≤ 89↗
DOE OSTI2019

Nuclear isovector valence-shell excitation of Hg 202

Excited states of 202 Hg have been studied via the 12 C( 202 Hg, 202 Hg*) Coulomb excitation reaction at a beam energy of 890 MeV. The γ-ray transitions from the excited states of 202 Hg were detected by the Gammasphere array. The intensities of the observed γ rays determined the relative populations of the excited states which were used to extract the absolute M 1 and E 2 transition strength distributions for excited 2 + states of 202 Hg up to 2 MeV. The measured absolute B ( M 1;2 + 7 →2 + 1 ) strength of 0.18(8)μ 2 N indicates that the 2 + 7 level of 202 Hg is the main fragment of the proton-neutron mixed-symmetry 2 + 1,ms state. As a result, the upper limits for the F -spin mixing matrix elements of 202,204 Hg are determined as well.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2019

Evolution of E 2 strength in the rare-earth isotopes Hf 174 , 176 , 178 , 180

Mean lifetimes of yrast states of the isotopes 174,176,178,180 Hf have been measured using fast-electronic scintillation timing. Excited states of 174,176,178 Hf were populated via β decay, while 180 Hf was populated via Coulomb excitation. The lifetimes of the 2 + 1 and 4 + 1 states of all isotopes and the lifetimes of the 6 + 1 states of 174,178 Hf were measured, using the slope and the centroid shift methods. The mean lifetime, τ(4 + 1 ) = 85 (13) ps, of 178 Hf has been determined for the first time. In addition, the mean lifetimes of the 2 – 1 and the 3 – 1 states of 176 Hf have been determined. Systematic uncertainties on the evolution of data as a function of neutron number were reduced by using the same setup for all the isotopes of interest. The data are in agreement with other recent lifetime measurements where available and shows a shift of the maximum of collectivity for the Hf isotopic chain from neutron midshell at N = 104 to N = 100.

150 ≤ A ≤ 189↗
DOE OSTI2015

Ground-state and pairing-vibrational bands with equal quadrupole collectivity in 124 Xe

The nuclear structure of 124 Xe has been investigated via measurements of the β + /EC decay of 124 Cs with the 8π γ-ray spectrometer at the TRIUMF-ISAC facility. The data collected have enabled branching ratio measurements of weak, low-energy transitions from highly excited states, and the 2 + → 0 + in-band transitions have been observed. Combining these results with those from a previous Coulomb excitation study, $B(E2; 2^+_3 → 0^+_2)$ = 78(13) W.u. and $B(E2; 2^+_4 → 0^+_3)$ = 53(12) W.u. were determined. The $0^+_3$ state, in particular, is interpreted as the main fragment of the proton-pairing vibrational band identified in a previous 122 Te( 3 He,n) 124 Xe measurement, and has quadrupole collectivity equal to, within uncertainty, that of the ground-state band.

74 ATOMIC AND MOLECULAR PHYSICS↗
NASA NTRS1978

Proton collisional excitation in the ground configuration of Fe/11+/

Proton collisional excitation cross sections at solar coronal energies for the Fe(11+) /3S(2)3p(3)/ ground-configuration transitions are presented. Semiclassical Coulomb excitation theory is used with direct integration of the resulting Schroedinger equation. The rate constants at coronal temperatures are compared with the corresponding ones for electron impact excitation.

Landman, D. A.↗
NASA NTRS1975

Proton collisional excitation in the ground configurations of Fe/+12/ and Fe/+13/. III - Transitions between magnetic sublevels

Values of proton collisional cross-sections at coronal energies have been computer for all transitions between magnetic sublevels of the Fe(+12) and Fe(+13) ground configurations. Semiclassical Coulomb excitation theory was used with the resulting truncated Schroedinger equations being directly integrated. The corresponding rate constants for coronal temperatures are presented and comparison is made with previous results.

Landman, D. A.↗