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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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11 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

High-accuracy multi-configuration Dirac–Hartree–Fock calculations of the energy levels and transition properties of Ga-like to Br-like gadolinium ions

Highlights: • A complete and accurate data set of excitation energies, lifetimes, wavelengths and E1, M1, E2, M2 and E3 line strengths, transition rates, and oscillator strengths for Ga-like to Br-like Gd ions is reported. • The Multi-configuration Dirac–Hartree–Fock method is employed. • The effects of core–valence electron correlation from the deep subshells 3d and 3p have been investigated. • The computed excitation energies from the present MCDHF calculations of the VV+CV{sub 3d}+CV{sub 3p} model agree well with the experimental values. The differences are less than ±0.1% for most of the levels. - Abstract: Theoretical calculations of Ga-like to Br-like gadolinium ions were performed by using the fully relativistic multi-configuration Dirac–Hartree–Fock (MCDHF) method. Extensive lists of excitation energies, wavelengths, line and oscillator strengths, and E1, M1, E2, M2, and E3 transition rates are presented. The effects of core–valence electron correlation from the deep subshells 3d and 3p are investigated and the accuracy of the results is confirmed by comparing with available theoretical and experimental data sets.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2010

Intense few-cycle hard-UV-pulse-induced internal conversion processes

The internal conversion coefficient for bound-free electron transition of originally energetically forbidden internal conversion processes induced by intense, few-cycle UV laser pulse of Gaussian shape in the case of isomers {sup 107}Ag{sup m} (K shell, E3, 25.47 keV), {sup 90}Nb{sup m} (L{sub 2} shell, M2+E3, 2.3 keV), {sup 183}W{sup m1}(M{sub 5} shell, E2, 1.79 keV), {sup 183}W{sup m2} (N{sub 1} shell, E1, 548 eV), and {sup 188}Re{sup m} (M{sub 2} shell, M3+E4, 2.63 keV), and {sup 235}U{sup m} (O{sub 4} and O{sub 5} shells, E3, 73.5 eV) is determined numerically. Experimental conditions and possibilities of the laser-induced internal conversion process of {sup 183}W{sup m2} from the N{sub 1} shell are discussed in more detail.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2011

Dependence of the probabilities of the electric-multipole electron transitions in W{sup 24+} on multipolarity

Usually it is accepted that the probabilities of the electric-multipole electron transitions are rapidly decreasing functions of their multipolarity. Therefore while calculating the probabilities of electronic transitions between the configurations of certain chosen parities, it seems sufficient to take into account the first nonzero term, i.e., to consider the electron transitions of lowest multipolarity permitted by the exact selection rules. This paper aims at verifying this assumption on the example of electric-octupole transitions in W{sup 24+} ion. For this purpose the large-scale multiconfiguration Hartree-Fock and Dirac-Fock calculations have been performed for the configurations [Kr]4d{sup 10}4f{sup 4} and [Kr]4d{sup 10}4f{sup 3}5s energy levels of W{sup 24+} ion. The relativistic corrections were taken into account in the quasirelativistic Breit-Pauli and fully relativistic Breit (taking into account QED effects) approximations. The role of correlation, relativistic, and QED corrections is discussed. Line strengths, oscillator strengths, and transition probabilities in Coulomb and Babushkin gauges are presented for E1 and E3 transitions among these levels.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

Blackbody radiation shift, multipole polarizabilities, oscillator strengths, lifetimes, hyperfine constants, and excitation energies in Hg{sup +}

Excitation energies of the [Xe]4f{sup 14}5d{sup 10}ns, [Xe]4f{sup 14}5d{sup 10}np{sub j}, [Xe]4f{sup 14}5d{sup 10}nd{sub j}, [Xe]4f{sup 14}5d{sup 10}n{sup '}f{sub j}, and [Xe]4f{sup 14}5d{sup 10}n{sup '}g{sub j} states in Hg{sup +} are evaluated (n{<=}10, n{sup '}{<=}9, and [Xe]=1s{sup 2}2s{sup 2}2p{sup 6}3s{sup 2}3p{sup 6}3d{sup 10}4s{sup 2}4p{sup 6}4d{sup 10}5s{sup 2}5p{sup 6}). First-, second-, third-, and all-order Coulomb energies and first- and second-order Coulomb-Breit energies are calculated. Reduced matrix elements, oscillator strengths, and transition rates are determined for electric-dipole transitions, including the ns (n=6-11), np (n=6-10), nd (n=6-10), nf (n=5-9), and ng (n=5-9) states. Lifetime values are determined for all above-mentioned states. The ground state E1, E2, and E3 polarizabilities are evaluated. The hyperfine structure in {sup 199}Hg{sup +} and {sup 201}Hg{sup +} ions is investigated. The hyperfine A and B values are determined for the first low-lying levels up to n = 7. The quadratic Stark effect on hyperfine structure levels of {sup 199}Hg{sup +} and {sup 201}Hg{sup +} ground states is investigated. The calculated shift for the {sup 199}Hg{sup +} (F = 1, M = 0) {r_reversible} (F = 0, M = 0) transition is -0.0597(2) Hz/(kV/cm){sup 2}, in agreement with previous theoretical result -0.060(3) Hz/(kV/cm){sup 2}. These calculations provide a theoretical benchmark for comparison with experiment and theory and provide values of blackbody radiation shifts for microwave frequency standards with {sup 199}Hg{sup +} and {sup 201}Hg{sup +} ions.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2011

Correlation and relativistic effects in actinide ions

Wavelengths, line strengths, and transition rates are calculated for the multipole (E1, M1, E2, M2, E3, and M3) transitions between the excited 6s{sup 2}6p{sup 5}nl and 6s6p{sup 6}nl states and the ground 6s{sup 2}6p{sup 6} state in Ac{sup 3+}, Th{sup 4+}, and U{sup 6+} Rn-like ions. Relativistic many-body perturbation theory (RMBPT), including the Breit interaction, is used to evaluate energies and transition rates for multipole transitions in these hole-particle systems. The RMBPT method agrees with multiconfigurational Dirac-Fock (MCDF) calculations in lowest order, includes all second-order correlation corrections, and includes corrections from negative-energy states. The calculations start from a [Xe]4f{sup 14}5d{sup 10}6s{sup 2}6p{sup 6} Dirac-Fock potential. First-order perturbation theory is used to obtain intermediate-coupling coefficients, and second-order RMBPT is used to determine the matrix elements. Evaluated multipole matrix elements for transitions from excited states to the ground states are used to determine the line strengths, transition rates, and multipole polarizabilities. This work provides a number of yet unmeasured properties of these actinide ions for various applications and for benchmark tests of theory and experiment.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2010

Isomer spectroscopy of {sup 127}Cd

The spin and configurational structure of excited states of {sup 127}Cd, the two-proton and three-neutron hole neighbor of {sup 132}Sn, has been studied. An isomeric state with a half-life of 17.5(3) {mu}s was populated in the fragmentation of a {sup 136}Xe beam on a {sup 9}Be target at a beam energy of 750 MeV/u. Time distributions of the delayed {gamma} transitions and {gamma}{gamma} coincidence relations were exploited to construct a decay scheme. The observed yrast (19/2){sup +} isomer is proposed to have dominant configurations of {nu}(h{sub 11/2}{sup -3}){pi}(g{sub 9/2}{sup -1},p{sub 1/2}{sup -1}), {nu}(h{sub 11/2}{sup -2}d{sub 3/2}{sup -1}){pi}(g{sub 9/2}{sup -2}), and {nu}(h{sub 11/2}{sup -2},s{sub 1/2}{sup -1}){pi}(g{sub 9/2}{sup -2}) and to decay by two competing stretched M2 and E3 transitions. Experimental results are compared with the isotone {sup 129}Sn. The new information provides input for the proton-neutron interaction and the evolution of neutron hole energies in nuclei around the doubly magic {sup 132}Sn core.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2011

Coulomb excitation of {sup 156}Gd

Multiple Coulomb-excitation experiments for {sup 156}Gd were made with a 118 MeV {sup 32}S beam and a 225 MeV {sup 58}Ni beam. The ground-state band, the {beta} band (K=0{sup +}), another K=0{sup +} band, and the {gamma} band (K=2{sup +}) were observed up to the 18{sup +}, 14{sup +}, 8{sup +}, and 12{sup +} states, respectively, while the octupole band (K=1{sup -}) was observed up to the 15{sup -} state, through the analysis of particle-{gamma}-{gamma} data. Compared with the results of the in-beam {gamma}-ray spectroscopy previously obtained, the present result suggests that a band crossing occurs in the {gamma} band. As for the {beta} band, the excitation energy of the 12{sup +} state was revised and the 14{sup +} state was newly observed in the present experiment. The intrinsic matrix elements entering the generalized intensity relations were obtained so as to reproduce the spin dependence of the E2 matrix elements extracted from the experimental results of particle-{gamma} angular correlation for the transitions within each band and between each band and the ground-state band by the least-squares search code gosia. The change of characters in the {beta} and {gamma} bands is discussed as a possible cause for the variation of the E2 matrix elements in the higher-spin region. The intrinsic matrix elements were also obtained for the E1 and E3 transitions from the ground-state band to the octupole band with K=1{sup -} through analysis by gosia.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2011

Identification of the slow E3 transition {sup 136}Cs{sup m{yields}136}Cs with conversion electrons

We performed at ISOLDE the spectroscopy of the decay of the 8{sup -} isomer in {sup 136}Cs by {gamma} and conversion-electron detection. For the first time the excitation energy of the isomer and the multipolarity of its decay have been measured. The half-life of the isomeric state was remeasured to T{sub 1/2}=17.5(2) s. This isomer decays via a very slow 518-keV E3 transition to the ground state. In addition to this, a much weaker decay branch via a 413-keV M4 and a subsequent 105-keV E2 transition has been found. Thus we have found a new level at 105 keV with spin 4{sup +} between the isomeric and the ground state. The results are discussed in comparison to shell-model calculations.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2015

Annual Continuation And Progress Report For Low-Energy Nuclear Physics Research At Lawrence Livermore National Laboratory

(I)In this project, the Beta-­decay Paul Trap, an open-­geometry RFQ ion trap that can be instrumented with sophisticated radiation detection arrays, is used for precision β-­decay studies. Measurements of β-­decay angular correlations, which are sensitive to exotic particles and other phenomena beyond the Standard Model (SM) of particle physics that may occur at the TeV-­energy scale, are being performed by taking advantage of the favorable properties of the mirror 8 Li and 8 B β ± decays and the benefits afforded by using trapped ions. By detecting the β and two α particles emitted in these decays, the complete kinematics can be reconstructed. This allows a simultaneous measurement of the β-­n, β-­n-­α, and β-α correlations and a determination of the neutrino energy and momentum event by event. In addition, the 8 B neutrino spectrum, of great interest in solar neutrino oscillation studies, can be determined in a new way. Beta-­delayed neutron spectroscopy is also being performed on neutron-­rich isotopes by studying the β-­decay recoil ions that emerge from the trap with high efficiency, good energy resolution, and practically no backgrounds. This novel technique is being used to study isotopes of mass-­number A~130 in the vicinity of the N=82 neutron magic number to help understand the rapid neutron-­capture process (r-­process) that creates many of the heavy isotopes observed in the cosmos. (II)A year-long CHICO2 campaign at ANL/ATLAS together with GRETINA included a total of 10 experiments, seven with the radioactive beams from CARIBU and three with stable beams, with 82 researchers involved from 27 institutions worldwide. CHICO2 performed flawlessly during this long campaign with achieved position resolution matching to that of GRETINA, which greatly enhances the sensitivity in the study of nuclear γ-­ray spectroscopy. This can be demonstrated in our results on 144 Ba and 146 Ba where the octupole deformation is evident from the measured B(E3; 3 - →0 + ) strengths that significantly greater than the theoretical predictions. We anticipate that CHICO2 will continue to be a viable charged-­particle detector for the research need of the low-­energy nuclear physics community.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2016

Extended calculations with spectroscopic accuracy: Energy levels and transition properties for the fluorine-like isoelectronic sequence with Z = 24–30

We have performed extensive multiconfiguration Dirac–Hartree–Fock calculations and second-order many-body perturbation calculations for F-like ions with Z = 24–30. Energy levels and transition rates for electric dipole (E1), electric-quadrupole (E2), electric-octupole (E3), magnetic dipole (M1), and magnetic-quadrupole (M2) transitions, as well as radiative lifetimes, are provided for the lowest 200 levels belonging to the 1s{sup 2}2s{sup 2}2p{sup 5}, 1s{sup 2}2s2p{sup 6}, 1s{sup 2}2s{sup 2}2p{sup 4}3l, 1s{sup 2}2s2p{sup 5}3l, 1s{sup 2}2p{sup 6}3l, and 1s{sup 2}2s{sup 2}2p{sup 4}4l configurations of each ion. The results from the two sets of calculations are in excellent agreement. Extensive comparisons are also made with other theoretical results and observed data from the CHIANTI and NIST databases. The present energies and wavelengths are believed to be accurate enough to aid line identifications involving the n = 3 and n = 4 configurations, for which observations are largely missing. The calculated wavelengths and transition data will be useful in the modeling and diagnostics of astrophysical and fusion plasmas.

74 ATOMIC AND MOLECULAR PHYSICS↗