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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 1,513 records · Page 84
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Off-Shell Persistence of Composite Pions and Kaons

In order for a Sullivan-like process to provide reliable access to a meson target as t becomes spacelike, the pole associated with that meson should remain the dominant feature of the quarkantiquark scattering matrix and the wave function describing the related correlation must evolve slowly and smoothly. Using continuum methods for the strong-interaction bound-state problem, we explore and delineate the circumstances under which these conditions are satisfied: for the pion, this requires -t ≲ 0.6 GeV 2 , whereas -t ≲ 0.9 GeV 2 will suffice for the kaon. Furthermore, these results should prove useful in evaluating the potential of numerous experiments at existing and proposed facilities.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2018

Mass measurements of neutron-rich indium isotopes toward the N = 82 shell closure

Precise mass measurements of the neutron-rich 125–130 In isotopes have been performed with the TITAN Penning trap mass spectrometer. TITAN's electron beam ion trap was used to charge breed the ions to charge state q = 13+ thus providing the necessary resolving power to measure not only the ground states but also isomeric states at each mass number. Here, the properties of the ground states are investigated through a series of mass differentials, highlighting trends in the indium isotopic chain as compared to its proton-magic neighbor, tin (Z = 50). In addition, the energies of the indium isomers are presented. The (8 - ) level in 128 In is found to be 78 keV lower than previously thought and the (21/2 - ) isomer in 127 In is shown to be lower than the literature value by more than 150 keV.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2018

Structure of the exotic He 9 nucleus from the no-core shell model with continuum

Here, the exotic 9 He nucleus, which presents one of the most extreme neutron-to-proton ratios, belongs to the N = 7 isotonic chain famous for the phenomenon of ground-state parity inversion with decreasing number of protons. Consequently, it would be expected to have an unnatural (positive) parity ground state similar to 11 Be and 10 Li. Despite many experimental and theoretical investigations, its structure remains uncertain. Apart from the fact that it is unbound, other properties including the spin and parity of its ground state, and the very existence of additional low-lying resonances are still a matter of debate

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2018

Sub-shell closure and shape coexistence in the transitional nucleus Zr 98

In the rapid shape change from spherical to deformed nuclei in the Z=40 Zr isotopic chain, recent work has identified shape coexistence in 96 Zr. Between 96 Zr and the strongly deformed 100 Zr, 98 Zr is expected to also exhibit coexistence of nuclear shapes. The degree of mixing between different configurations is mainly determined by the nucleon-nucleon interactions. For nuclear model predictions, experimental constraints are needed, but they are barely available for 98 Zr. To study low-lying transitions in 98 Zr, a Coulomb excitation experiment was conducted at the Argonne Tandem-Linac Accelerator System (ATLAS) facility using a 98 Zr beam extracted from the Californium Rare Ion Breeder Upgrade (CARIBU) ion source and Gamma-Ray Energy Tracking In-beam Nuclear Array (GRETINA) for γ-ray spectroscopy coupled to the compact heavy ion counter (CHICO2) for ion detection. Furthermore, this paper reports on the first decisive deduction of the B(E2;2 + 1 →0 + 1 ) transition strength in 98 Zr and on its interpretation.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
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

Informing direct neutron capture on tin isotopes near the N = 82 shell closure

Half of the elements heavier than iron are believed to be produced through the rapid neutron-capture process ($r$-process). The astrophysical environment(s) where the $r$-process occurs remains an open question, even after recent observations of neutron-star mergers and the associated kilonova. Features in the abundance pattern of $r$-process ashes may provide critical insight for distinguishing contributions from different possible sites, including neutron-star mergers and core-collapse supernovae. In particular, the largely unknown neutron-capture reaction rates on neutron-rich unstable nuclei near 132 Sn could have a significant impact on the final $r$-process abundances. To better determine these neutron-capture rates, the ($d,p$) reaction has been measured in inverse kinematics using radioactive ion beams of 126 Sn and 128 Sn and a stable beam of 124 Sn interacting with a (CD 2 )$_n$ target. An array of position-sensitive silicon strip detectors, including the Super Oak Ridge Rutgers University Barrel Array, was used to detect light reaction products. In addition to the present measurements, previous measurements of 130,132 Sn($d,p$) were reanalyzed using state-of-the-art reaction theory to extract a consistent set of spectroscopic factors for ($d,p$) reactions on even tin nuclei between the heaviest stable isotope 124 Sn and doubly magic 132 Sn. The spectroscopic information was used to calculate direct-semidirect ($n,γ$) cross sections, which will serve as important input for r-process abundance calculations.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗