Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “FALLON”

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 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Decay spectroscopy of element 115 daughters: Rg 280 → Mt 276 and Mt 276 → Bh 272

In this study, forty-six decay chains, assigned to the decay of 288 115, were produced using the 243 Am ( 48 Ca, 3n) 288 115 reaction at the Lawrence Berkeley National Laboratory 88-in. cyclotron. The resulting series of α decays were studied using α-photon and α-x-ray spectroscopies. Multiple α-photon coincidences were observed in the element 115 decay chain members, particularly in the third- and fourth-generation decays (presumed to be 280 Rg and 276 Mt, respectively). Upon combining these data with those from 22 288 115 decay chains observed in a similar experiment, updated level schemes in 276 Mt and 272 Bh (populated by the α decay of 280 Rg and 276 Mt, respectively) are proposed. Additionally, photons were observed in the energy range expected for K x rays coincident with the α decay of both 280 Rg and 276 Mt. However, Compton scattering of higher-energy γ rays and discrete transitions are present in the K x-ray region preventing a definitive Z identification to be made based on observation of characteristic K x-ray energies.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2015

Toward complete spectroscopy of 167 Lu

Excited states in 167 Lu were populated in the 123 Sb( 48 Ca,4n) reaction at 203 MeV and decay γ rays measured using the Gammasphere spectrometer array. Two triaxial strongly deformed bands were identified previously and interpreted as zero- and one-phonon wobbling excitations. As a result of more extensive band search, the level scheme has been considerably extended to include ten new rotational bands and some 630γ-ray transitions. A number of interband linking transitions were revealed, so that all but two bands could be connected with each other. Configurations are proposed for all new bands based on measured observables, with the help of cranked shell model calculations. A γ-ray sequence, previously suggested as a triaxial strongly deformed band based on quasiparticle excitations coexisting with the wobbling excitation in the triaxial potential well, has now been determined to be a signature partner of a coupled band, associated with a normal deformed five-quasiparticle configuration. Here, the possibility of two new bands being associated with triaxial deformation is discussed.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2015

Lifetime measurements of C 17 excited states and three-body and continuum effects

We studied transition rates for the lowest 1/2 + and 5/2 + excited states of 17 C through lifetime measurements with the GRETINA array using the recoil-distance method. The present measurements provide a model-independent determination of transition strengths giving the values of B(M1;1/2 + →3/2$+\atop{g.s}$)=1.04$+0.03\atop{-0.12}$ ×10 -2 μ$2\atop{N}$ and B(M1;5/2 + →3/2$+\atop{g.s}$)=7.12$+1.27\atop{-0.96}$×10 -2 μ$2\atop{N}$. The quenched M1 transition strength for the 1/2+→3/2$+\atop{g.s}$ transition, with respect to the 5/2 + →3/2$+\atop{g.s}$ transition, has been confirmed with greater precision. The current data are compared to importance-truncated no-core shell model calculations addressing effects due to continuum and three-body forces.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2016

γ-ray decay from neutron-bound and unbound states in 95 Mo and a novel technique for spin determination

The emission of γ rays from neutron-bound and neutron-unbound states in 95 Mo, populated in the 94 Mo(d,p) reaction, has been investigated. Charged particles and γ radiation were detected with arrays of annular silicon and Clover-type high-purity Germanium detectors, respectively. Utilizing p-γ and p-γ-γ coincidences, the 95 Mo level scheme was greatly enhanced with 102 new transitions and 43 new states. It agrees well with shell model calculations for excitation energies below ≈2 MeV. From p-γ coincidence data, a new method for the determination of spins of discrete levels is proposed. The method exploits the suppression of high-angular momentum neutron emission from levels with high spins populated in the (d,p) reaction above the neutron separation energy. As a result, spins for almost all 95 Mo levels below 2 MeV (and for a few levels above) have been determined with this method.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2016

Z = 50 core stability in 110 Sn from magnetic-moment and lifetime measurements

In this study, the structure of the semimagic Sn50 isotopes were previously studied via measurements of B(E2;2 1 + → 0 1 + ) and g factors of 2 1 + states. The values of the B(E2;2 1 + ) in the isotopes below midshell at N = 66 show an enhancement in collectivity, contrary to predictions from shell-model calculations. This work presents the first measurement of the 2 1 + and 4 1 + states' magnetic moments in the unstable neutron-deficient 110 Sn. The g factors provide complementary structure information to the interpretation of the observed B(E2) values.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2016

High-spin structure of Xe 134

Detailed spectroscopic information on the N~82 nuclei is necessary to benchmark shell-model calculations in the region. The nuclear structure above long-lived isomers in 134 Xe is investigated after multinucleon transfer (MNT) and actinide fission. Xenon-134 was populated as (i) a transfer product in 136 Xe+ 238 U and 136 Xe+ 208 Pb MNT reactions and (ii) as a fission product in the 136 Xe+ 238 U reaction employing the high-resolution Advanced Gamma Tracking Array (AGATA). Trajectory reconstruction has been applied for the complete identification of beamlike transfer products with the magnetic spectrometer PRISMA. The 136 Xe+ 198 Pt MNT reaction was studied with the γ-ray spectrometer GAMMASPHERE in combination with the gas detector array Compact Heavy Ion Counter (CHICO). Several high-spin states in 134 Xe on top of the two long-lived isomers are discovered based on γγ-coincidence relationships and information on the γ-ray angular distributions as well as excitation energies from the total kinetic energy loss and fission fragments. The revised level scheme of 134 Xe is extended up to an excitation energy of 5.832 MeV with tentative spin-parity assignments up to 16 + . Previous assignments of states above the 7 - isomer are revised. Latest shell-model calculations employing two different effective interactions reproduce the experimental findings and support the new spin and parity assignments.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2016

Properties of isoscalar-pair condensates

In this work, it is pointed out that the ground state of $n$ neutrons and n protons in a single-$j$ shell, interacting through an isoscalar ($T=0$) pairing force, is not paired, $J=0$, but rather spin aligned, $J=n$. This observation is explained in the context of a model of isoscalar $P(J=1)$ pairs, which is mapped onto a system of $p$ bosons, leading to an approximate analytic solution of the isoscalar-pairing limit in $jj$ coupling.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2016

Magnetic moment and lifetime measurements of Coulomb-excited states in Cd 106

The Cd isotopes are well studied, but experimental data for the rare isotopes are sparse. At energies above the Coulomb barrier, higher states become accessible. Remeasure and supplement existing lifetimes and magnetic moments of low-lying states in 106 Cd. Methods: In an inverse kinematics reaction, a 106 Cd beam impinging on a 12 C target was used to Coulomb excite the projectiles. The high recoil velocities provide a unique opportunity to measure g factors with the transient-field technique and to determine lifetimes from lineshapes by using the Doppler-shift-attenuation method. Large-scale shell-model calculations were carried out for 106 Cd. As a result, the g factors of the 2 + 1 and 4 + 1 states in 106 Cd were measured to be g(2 + 1 ) = +0.398(22) and g(4 + 1 ) = +0.23(5). A lineshape analysis yielded lifetimes in disagreement with published values. The new results are τ( 106 Cd; 2 + 1 ) = 7.0(3) ps and τ( 106 Cd; 4 + 1 ) = 2.5(2) ps. The mean life τ( 106 Cd; 2 + 2 ) = 0.28(2) ps was determined from the fully-Doppler-shifted γ line. Mean lives of τ( 106 Cd; 4 + 3 ) = 1.1(1) ps and τ( 106 Cd; 3 – 1 ) = 0.16(1) ps were determined for the first time. In conclusion, the newly measured g(4 + 1 ) of 106 Cd is found to be only 59% of the g(2 + 1 ). This difference cannot be explained by either shell-model or collective-model calculations.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2016

Observation of high-spin bands with large moments of inertia in Xe 124

In this paper, high-spin states in 124 Xe have been populated using the 80 Se( 48 Ca, 4n) reaction at a beam energy of 207 MeV and high-multiplicity, γ-ray coincidence events were measured using the Gammasphere spectrometer. Six high-spin rotational bands with moments of inertia similar to those observed in neighboring nuclei have been observed. The experimental results are compared with calculations within the framework of the Cranked Nilsson-Strutinsky model. Finally, it is suggested that the configurations of the bands involve excitations of protons across the Z = 50 shell gap coupled to neutrons within the N = 50 - 82 shell or excited across the N = 82 shell closure.

124Xe deduced levels↗
DOE OSTI2016

The Mg 30 ( t , p ) Mg 32 “puzzle” reexamined

Background: Competing interpretations of the results of a Mg 30 (t,p)Mg 32 measurement populating the ground state and 0$+\atop{2}$ state in Mg 32 , both limited to a two-state mixing description, have left an open question regarding the nature of the Mg 32 ground state. Purpose: Inspired by recent shell-model calculations, we explore the possibility of a consistent interpretation of the available data for the low-lying 0 + states in Mg 32 by expanding the description from two-level to three-level mixing. Methods: A phenomenological three-level mixing model of unperturbed 0p0h, 2p2h, and 4p4h states is applied to describe both the excitation energies in Mg 32 and the transfer reaction cross sections. Results: Within this approach, self-consistent solutions exist that provide good agreement with the available experimental information obtained from the Mg 30 (t,p)Mg 32 reaction. Conclusion: The inclusion of the third state, namely the 4p4h configuration, resolves the "puzzle" that results from a two-levelmodel interpretation of the same data. In our analysis, the Mg 32 ground state emerges naturally as dominated by intruder (2p2h and 4p4h) configurations, at the 95% level.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2017

β decay of Si 38 , 40 ( T z = + 5 , + 6 ) to low-lying core excited states in odd-odd P 38 , 40 isotopes

Low-lying excited states in P 38,40 have been identified in the β decay of T z =+5,+6, Si 38,40 . Based on the allowed nature of the Gamow-Teller (GT) decay observed, these states are assigned spin and parity of 1 + and are core-excited 1p1h intruder states with a parity opposite to the ground state. The occurrence of intruder states at low energies highlights the importance of pairing and quadrupole correlation energies in lowering the intruder states despite the N=20 shell gap. Configuration interaction shell model calculations with the state-of-art SDPF-MU effective interaction were performed to understand the structure of these 1p1h states in the even-A phosphorus isotopes. States in P 40 with N=25 were found to have very complex configurations involving all the fp orbitals leading to deformed states as seen in neutron-rich nuclei with N≈28. The calculated GT matrix elements for the β decay highlight the dominance of the decay of the core neutrons rather than the valence neutrons.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2017

Isomers and high-spin structures in the N = 81 isotones Xe 135 and Ba 137

In this study, the high-spin structures and isomers of the N=81 isotones 135 Xe and 137 Ba are investigated after multinucleon-transfer (MNT) and fusion-evaporation reactions. Both nuclei are populated (i) in 136 Xe + 238 U and (ii) 136 Xe+ 208 Pb MNT reactions employing the high-resolution Advanced Gamma Tracking Array (AGATA) coupled to the magnetic spectrometer PRISMA, (iii) in the 136 Xe+ 198 Pt MNT reaction employing the γ-ray array GAMMASPHERE in combination with the gas-detector array CHICO, and (iv) via a 11 B+ 130 Te fusion-evaporation reaction with the HORUS γ-ray array at the University of Cologne. The high-spin level schemesof 135 Xe and 137 Ba are considerably extended to higher energies. The 2058-keV (19/2 - ) state in 135 Xe is identified as an isomer, closing a gap in the systematics along the N=81 isotones. Its half-life is measured to be 9.0(9) ns, corresponding to a reduced transition probability of B(E2,19/2 - →15/2 - )=0.52(6) W.u. The experimentally deduced reduced transition probabilities of the isomeric states are compared to shell-model predictions. Finally, latest shell-model calculations reproduce the experimental findings generally well and provide guidance to the interpretation of the new levels.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2017

Unexpected distribution of ν 1 f 7 / 2 strength in Ca 49

Here, the calcium isotopes have emerged as a critical testing ground for new microscopically derived shell-model interactions, and a great deal of experimental and theoretical focus has been directed toward this region. We investigate the relative spectroscopic strengths associated with 1f 7/2 neutron hole states in 47,49 Ca following one-neutron knockout reactions from 48,50 Ca. The observed reduction of strength populating the 7/2 – 1 state in 49 Ca, as compared to 47 Ca, is inconsistent with shell-model calculations using both phenomenological interactions such as GXPF1, and interactions derived from microscopically based two- and three-nucleon forces. The result suggests a fragmentation of the l = 3 strength to higher-lying states as suggested by the microscopic calculations, but the observed magnitude of the reduction is not reproduced in any shell-model description.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2017

Cross-shell excitations in Si 31

The Si-31 nucleus was produced through the O-18(18O, an) fusion-evaporation reaction at E-lab = 24 MeV. Evaporated a particles from the reaction were detected and identified in the Microball detector array for channel selection. Multiple gamma-ray coincidence events were detected in Gammasphere. The energy and angle information for the alpha particles was used to determine the Si-31 recoil kinematics on an event-by-event basis for a more accurate Doppler correction. A total of 22 new states and 52 new gamma transitions were observed, including 14 from states above the neutron separation energy. The positive-parity states predicted by the shell-model calculations in the sd model space agree well with experiment. The negative-parity states were compared with shell-model calculations in the psdpf model space with some variations in the N = 20 shell gap. The best agreement was found with a shell gap intermediate between that originally used for A approximate to 20 nuclei and that previously adapted for P-32,P-34. This variation suggests the need for a more universal cross-shell interaction.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2017

High-spin structures in Xe 132 and Xe 133 and evidence for isomers along the N = 79 isotones

In this study, the transitional nuclei 132 Xe and 133 Xe are investigated after multinucleon-transfer (MNT) and fusion-evaporation reactions. Both nuclei are populated (i) in 136 Xe + 208 Pb MNT reactions employing the high-resolution Advanced GAmma Tracking Array (AGATA) coupled to the magnetic spectrometer PRISMA, (ii) in the 136 Xe + 198 Pt MNT reaction employing the GAMMASPHERE spectrometer in combination with the gas-detector array CHICO, and (iii) as an evaporation residue after a 130 Te (α,xn) 134-xn Xe fusion-evaporation reaction employing the HORUS γ -ray array at the University of Cologne. The high-spin level schemes are considerably extended above the J π = (7 - ) and (10 + ) isomers in 132 Xe and above the 11/2 - isomer in 133 Xe. The results are compared to the high-spin systematics of the Z = 54 as well as the N = 78 and N = 79 chains. Furthermore, evidence is found for a long-lived (T 1/ 2 » 1 μs) isomer in 133 Xe which closes a gap along the N = 79 isotones. Finally, shell-model calculations employing the SN100PN and PQM130 effective interactions reproduce the experimental findings and provide guidance to the interpretation of the observed high-spin features.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗