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DOE OSTI2020

Landscape of pear-shaped even-even nuclei

The phenomenon of reflection-asymmetric nuclear shapes is relevant to nuclear stability, nuclear spectroscopy, nuclear decays and fission, and the search for new physics beyond the standard model. Global surveys of ground-state octupole deformation, performed with a limited number of models, suggest that the number of pear-shaped isotopes is fairly limited across the nuclear landscape. Here, we carry out a global analysis of ground-state octupole deformations for particle-bound even-even nuclei with Z ≤ 110 and N ≤ 210 using nuclear density functional theory (DFT) with several nonrelativistic and covariant energy density functionals. In this way, we can identify the best candidates for reflection-asymmetric shapes. The calculations are performed in the frameworks of axial reflection-asymmetric Hartree-Fock-Bogoliubov theory and relativistic Hartree-Bogoliubov theory using DFT solvers employing harmonic oscillator basis expansion. We consider five Skyrme and four covariant energy density functionals. We predict several regions of ground-state octupole deformation. In addition to the “traditional” regions of neutron-deficient actinide nuclei around 224 Ra and neutron-rich lanthanides around 146 Ba, we identified vast regions of reflection-asymmetric shapes in very neutron-rich nuclei around 200 Gd and 288 Pu, as well as in several nuclei around 112 Ba. Our analysis suggests several promising candidates with stable ground-state octupole deformation, primarily in the neutron-deficient actinide region, that can be reached experimentally. Detailed comparison between Skyrme and covariant models is performed. Octupole shapes predicted in this study are consistent with the current experimental information. This work can serve as the starting point of a systematic search for parity doublets in odd-mass and odd-odd nuclei, which will be of interest in the context of new physics searches.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2025

Fingerprints of Triaxiality in the Charge Radii of Neutron-Rich Ruthenium

We present the first measurements with a new collinear laser spectroscopy setup at the Argonne Tandem Linac Accelerator System, utilizing its unique capability to deliver neutron-rich refractory metal isotopes produced by the spontaneous fission of 252 Cf. We measured isotope shifts from optical spectra for nine radioactive ruthenium isotopes 106–114 Ru, reaching deep into the mid-shell region. The extracted charge radii are in excellent agreement with predictions from the Brussels-Skyrme-on-a-Grid models that account for the triaxial deformation of nuclear ground states. We show that triaxial deformation impacts charge radii in models that feature shell effects, in contrast to what could be concluded from a liquid drop analysis. This indicates that this exotic type of deformation should not be neglected in regions where it is known to occur, even if its presence cannot be unambiguously inferred through laser spectroscopy.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2025

Yrast structures of 98 Nb and 99 Mo

Neutron-rich nuclei in the A ≈ 100 mass region are interesting due to a rapid shape transition, especially pronounced in the Zr isotopes, and more recently observed in Nb isotopes. 98 Nb, with only one proton and one neutron outside the subshell closure nucleus of 96 Zr, is amenable to shell model calculations. To further examine the rapid shape transition the yrast structure of 98 Nb was established in this work. This was the only yrast structure missing from all immediate neighbors to 96 Zr. The yrast structure of 98 Nb was studied in the fission of the compound systems formed in three heavy-ion induced reactions, 24 Mg (134.5 MeV) + 173 Yb, 23 Na (129 MeV) + 176 Yb, and 18 O (91 MeV) + 208 Pb. Prompt γ-ray spectroscopy was accomplished using the Gammasphere array. Excitation energies up to 3 MeV were observed for the first time in 98 Nb. The yrast structure above the previously known (5) + isomer was established. In the process of studying 98 Nb the yrast structure of positive-parity states in 99 Mo was extended to 3.7 MeV excitation energy, the previously-known 99 Nb level scheme was enriched, and two new levels were added in the level scheme of 97 Zr. The coupling of the odd proton occupying the g 9/2 orbital to the yrast states in the core nucleus of 97 Zr can account for all observed states in 98 Nb. The yrast structure for the positive-parity states of 99 Mo is compared to the deformed ground-state bands of the 101 Ru isotone and of 98,100 Mo.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

NASA NTRS1989

Urey prize lecture - Water on Mars

Taking the heat-transport physics of ice-covered lakes in the Dry Valleys of Antarctica as a model, it is presently suggested that liquid water lakes could have persisted for significant periods under protective ice covers in the Valles Marineris depressions of Mars. Calculations of ground ice thermodynamic stability in a Martian setting indicate that they may exist close to the surface at high latitudes, but are able to persist near the equator only at substantial depths. Such Martian landforms as terrain-softening are attributable to the creep of the Martian regolith under the influence of ground-ice deformation; FEM modeling of the flow process implies terrain-softening to be a near-surface phenomenon.

Squyres, Steven W.↗

DOE OSTI2021

Oregon Roadway CSZ Liquefaction and Landslide Impact Screening Analysis

The roadway transportation routes and the surrounding environments in Oregon will be subject to ground acceleration and potential associated deformation due to the propagation of waves of energy during a Cascadia Subduction Zone (CSZ) earthquake. Linear features such as highways may be subject to partial or complete disruption of their function resulting from ground deformations at and along the roadway. A potential source of these disruptions associated with a CSZ event are landslides and liquefaction in the soils along and beneath the highways and local roadways. The construction of the Oregon roadway system and urban development have occurred largely along the banks of the rivers—those along the Pacific coast, and along the valleys throughout the Oregon Coast Range and Cascade Mountains. These locations also represent areas where landslides and liquefaction have occurred historically, or may potentially occur in the future, presenting a significant vulnerability for the roadway system and dependent post-CSZ earthquake emergency response and recovery effort. Many of the Oregon areas with landslide- and liquefaction-prone soils have the potential to impact roadway transportation routes after a major earthquake causing delays in establishing routes to transport emergency response personnel and resources to impacted areas and communities. This report presents methods used to project the impacts that CSZ earthquake-induced landslides and liquefaction may have on roadways across Oregon. First, this report presents an approach for estimating the risk of landslides to Oregon roadways, and determining approximate reopening times. Second, this report presents a similar approach for estimating the risk of liquefaction-induced ground displacements to roadway pavements, also resulting in approximate reopening times for roadway segments. The outcomes of these two ground failure analyses serve as inputs to a broader analysis of CSZ earthquake impacts to Oregon’s surface transportation system and its ability to support post-disaster response and recovery activities, as part of the Oregon Transportation Systems Regional Resiliency Assessment Program project (CISA 2021).

58 GEOSCIENCES↗

NASA NTRS1980

Crustal deformation at very long baseline interferometry sites due to seasonal air-mass and ground water variations

The seasonal deformation normal to the Earth's surface was calculated at stations involved or interested in very long baseline interferometry (VLBI) geodesy and at hypothetical sites in Australia and Brazil using global atmospheric pressure data, values for groundwater storage, and load Love numbers deduced from current Earth models. It was found that the annual range of deformation approached the centimeter level measuring potential of the VLBI technqiue at Greenbank, Haystack, and the Brazil site.

Stolz, A.↗

DOE OSTI2021

First observation of collective rotational bands in neutron-rich 142 La and the study of octupole/triaxial deformations in 142,143 La

Collective rotational bands were observed for the first time in neutron-rich odd–odd 142 La by means of γ-γ-γ and γ-γ-γ-γ coincidence measurements of prompt fission γ rays from 252 Cf using multi-detector array Gammasphere. Similarity between the yrast band of 142 La and those of neighboring 144 La, 144 Ce was found and interpreted as quasiparticle excitations. Here, PES calculations suggested triaxial deformation for the ground state of 142La. Considerable triaxial and near zero octupole deformations were deduced for the yrast band of 142 La by the TRS model calculations. The band-crossing observed in the yrast band of 142 La was interpreted to be caused by alignment of the (h 11/2 ) 2 proton pair, and the crossing frequency was best reproduced by the TRS calculations taking into account triaxial deformations. In contrast to the interpretations for the band crossing of 142 La, alignments of the (i 13/2 ) 2 neutron pair were found to be responsible for the band-crossing of the yrast band in the neighboring even-N 143 La, and triaxial degree of freedom was found to play a more significant role than octupole deformations in the nucleus, although its β 3 values deduced are large.

142La↗

DOE OSTI2023

Back-Azimuth Estimation of Air-to-Ground Coupled Infrasound from Transverse Coherence Minimization [Slides]

Infrasonic signals are generated by a variety of natural and anthropogenic sources and can propagate long distances through a windy, layered atmosphere. When these signals impinge on the ground, the resulting deformation can be recorded by buried seismometers, we call this signal a ground coupled airwave (GCA). GCAs are relatively common, and several methods now exist to leverage an infrasound microphone to separate GCAs from pure seismic motion.

47 OTHER INSTRUMENTATION↗

DOE OSTI2023

Spectroscopic quadrupole moments in 124 $\mathrm{Xe}$

The Xe isotopic chain with four valence protons above the Z=50 shell closure is an ideal laboratory for the study of the evolution of nuclear deformation. At the N=82 shell closure, 136 Xe presents all characteristics of a doubly closed shell nucleus with a spherical shape. In the very neutron-deficient isotopes close to N=50, the α-decay chain of Xe was investigated to probe the radioactive decay properties near the drip-line and the magicity of 100 Sn. Additionally, the Xe isotopes present higher order symmetries in the nuclear deformation such as the octupole degree of freedom near N=60 and N=90 or O(6) symmetry in stable isotopes. The relevance of the O(6) symmetry has been investigated by measuring the spectroscopic quadrupole moment of the first excited states in 124 Xe. In the O(6) symmetry limit, the spectroscopic quadrupole moment of collective states is expected to be null. A stable 124 Xe beam with energies of 4.03A MeV and 4.11 A MeV was used to bombard a nat W target at the GANIL facility. Excited states were populated via the safe Coulomb excitation reaction. The collision of the heavy ions with a large Z at low energy make this reaction sensitive to the diagonal E2 matrix element of the excited states. The recoils were detected in the VAMOS++ magnetic spectrometer and the γ rays in the AGATA tracking array. The least squares fitting code gosia was used for the analysis to extract both E2 and M1 transitional and E2 diagonal matrix elements. The rotational ground state band was populated up to the 8$^{+}_{1}$ state as well as the 2$^{+}_{2}$ and 4$^{+}_{2}$ states. Using high precision spectroscopic data to constrain the gosia fit, the spectroscopic quadrupole moments of the 2$^{+}_{1}$, 4$^{+}_{1}$, and 6$^{+}_{1}$ states were determined for the first time. The spectroscopic quadrupole moments were found to be negative, large, and constant in the ground state band underlining the prolate axially deformed ground state band of 124 Xe. Here, the present experimental data confirm that the O(6) symmetry is substantially broken in 124 Xe .

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2022

Research on Deformation Law of Deep Foundation Pit of Station in Core Region of Saturated Soft Loess Based on Monitoring

Saturated soft loess has a large pore structure, high compressibility, low strength, fluid plastic state, and poor engineering properties. It is still one of the key problems that engineering needs to solve. In order to study the influence of deep foundation pit excavation in the saturated soft loess area on the deformation of foundation pits, the deformation laws of ground settlement, enclosure structure, and supporting axial force were clarified based on the field tests on the deformation characteristics of deep foundation pits in areas with the high-water level in saturated soft loess, combined with geological conditions and on-site construction procedures. The results indicate the following: water supply and construction process were found to be the main factor in changing the surface settlement curve of deep foundation pits in saturated soft loess; increasing the construction speed of the pit bottom floor, inverted braces, floor frame beams, and sidewall frame beams to close the structure, which is conducive to restraining the deformation of the continuous underground wall and foundation pits in similar areas. In the initial stage of support layout, the axial force of steel support tends to increase too fast or even exceed the standard control value. Therefore, a reasonable preadding axial force is an effective means to control the deformation of the continuous underground wall and the axial force of the steel support. The current research results may provide a reference for constructing deep foundation pits in similar areas.

Wang, Xueyan↗

NASA NTRS1974

The response of many-storied structures under seismic actions

A seismic action which is characterized by the acceleration function of the seismic motion is analyzed. The equations of motion in the direction of the seismic action are determined for a completely rigid ground and for a ground with linear deformability characteristics (rotation deformability). The equation for the rotation motion is derived by considering elastic and viscoelastic properties of the foundation ground. The differential equations are written by treating the mechanical model of a many-storied structure as a fixed vertical beam with a uniformly distributed mass as well as with concentrated masses on each floor.

Munteanu, K.↗

NASA NTRS2020

Comparison of Vertical Surface Deformation Estimates Derived From Space-Based Gravimetry, Ground-Based GPS, and Model-Based Hydrologic Loading Over Snow-Dominated Watersheds in the United States

Spatiotemporal variability in Earth's terrestrial water storage (TWS) causes changes in surface deformation. The potential for using ground-based Global Positioning System (GPS) vertical displacement observations for estimating TWS is explored through a comparison of vertical displacements derived from space-based gravimetric retrievals, ground-based GPS, and model-based hydrologic estimates. The study presented here focuses on two snow-dominated basins in the Western United States for the years 2003–2016. Seasonal variations are observed in the vertical displacements derived from all three data sets, and the variation is coherent with the changes in hydrologic loading. Good consistency is observed between any two of the three data sets with gravimetric retrievals and hydrologic model estimates providing the highest level of agreement (i.e., all examined stations with correlation coefficient R > 0.70). Vertical displacements derived from gravimetric retrievals and ground-based GPS yielded R > 0.70 for more than 89% of the stations. In addition, it is found that both GPS-derived and space-based, gravimetry-derived vertical displacements clearly reflected the impact of climate variation (i.e., heavy precipitation during 2010–2011 winter followed by prolonged drought). Vertical displacements derived from the hydrologic model highlighted the relatively large precipitation convergence phase during late 2010 to early 2011 at some stations but not the prolonged drought that followed. The results indicate that ground-based GPS observations of vertical displacement have the capability to capture variations in TWS changes, which can be systematically merged in conjunction with Gravity Recovery and Climate Experiment (GRACE) into a land surface model to improve TWS estimates in a follow-up study.

Gaohong Yin↗

DOE OSTI2022

Naturally Self-Tuned Low Mass Composite Scalars

Scalar bosons composed of a pair of chiral fermions in a non-confining potential have an effective Yukawa coupling, $g$, to free external chiral fermions. At large distance a Feynman loop of external fermions generates a scale invariant potential, $V_{loop}\propto -g^2/{\rho^{2}}$, for separation $\rho$, which acts on valence fermions. This generally forces the $s$-wave ground state to deform to a static, zero mass, configuration, and for slowly running, perturbative $g$, a large external "shroud" wave function forms. This is related to old results of Landau and Lifshitz in quantum mechanics. The massless composite scalar boson ground state is then an extended object. Infra-red effects can generate a small mass for the system. This points to a perturbative BEH-boson composed of top and anti-top quarks and a novel dynamical mechanism for spontaneous electroweak symmetry breaking.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2023

Probing triaxiality beyond the proton drip line: Spectroscopy of Tm 147

Two triaxial states of the proton-decaying nucleus 147 Tm were studied via a comparison of experimental data to results obtained through nonadiabatic quasiparticle calculations. The experimental data were collected in a recoil-decay tagging study using the vacuum-mode recoil separator MARA coupled with the JUROGAM3 $\gamma$-ray spectrometer. The previously proposed level scheme above the triaxial 11/2 - (π⁢ℎ 11/2 ) ground state was confirmed, and the level structure was expanded to cover the states above the weakly populated proton-emitting 5/2 + (πd 5/2 ) isomeric state. Further, it was found that the isomeric state is also triaxial, and possibly more deformed than the ground state.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

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↗

NASA NTRS2004

On Physical Interpretation of the In-Site Measurement of Earth Rotation by Ring Laser Gyrometers

Large ring laser gyrometers under development have demonstrated the capability of detecting minute ground motions and deformations on a wide range of timescales. The next challenge and goal is to measure the Earth's rotation variations to a precision that rivals that of the present space-geodesy techniques, thus providing an in-situ (and cost effective alternatives of Earth rotation measurement for geophysical research and geodetic applications. Aside from thermal and mechanical instabilities, "undesirable" ground motion and tilt that appear in the signal will need to be removed before any variation in Earth rotation can be detected. Removal of these signals, some of them are larger than the sought rotation signals, has been a typical procedure in many precise geophysical instruments, such as gravimeters, seismometers, and tiltmeters. The remaining Earth rotation signal resides in both the spin around the axis and in the orientation of the axis. In the case of the latter, the in-situ measurement is complementary to the space-geodetic observables in terms of polar motion and nutation, a fact to be exploited.

Chao, B. F.↗

DOE OSTI2021

Contribution of Electron Pressure to Ring Current and Ground Magnetic Depression Using RAM-SCB Simulations and Arase Observations During 7–8 November 2017 Magnetic Storm

Understanding the physical processes that control the dynamics of energetic particles in the inner magnetosphere is important for both space-borne and ground-based assets essential to the modern society. The storm time distribution of ring current particles in the inner magnetosphere depends strongly on their transport in the evolving electric and magnetic fields along with particle acceleration and loss. Here, we investigated the ring current particle variations using observations and simulations. We compared the ion (H + , He + , and O + ) and electron flux and plasma pressure variations from Arase observations with the self-consistent inner magnetosphere model: Ring current Atmosphere interactions Model with Self Consistent magnetic field (RAM-SCB) during the 7–8 November 2017 geomagnetic storm. We investigated the contribution of the different species (ions and electrons) to the magnetic field deformation observed at ground magnetic stations (09°–45° MLat) using RAM-SCB simulations. The results show that the ions are the major contributor with ~88% and electrons contribute ~12% to the total ring current pressure. It is also found that the electron contribution is non-negligible (~18%) to the ring current in dawn-side during the main phase of the storm. Thus, the electron contribution to the storm time ring current is important and should not be neglected.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2021

T$ \overline{T} $ deformation in SCFTs and integrable supersymmetric theories

We calculate the $ \mathcal{S} $ -multiplets for two-dimensional Euclidean $ \mathcal{N} $ = (0 , 2) and $ \mathcal{N} $ = (2 , 2) superconformal field theories under the T $ \overline{T} $ deformation at leading order of perturbation theory in the deformation coupling. Then, from these $ \mathcal{N} $ = (0 , 2) deformed multiplets, we calculate two- and three-point correlators. We show the $ \mathcal{N} $ = (0 , 2) chiral ring’s elements do not flow under the T $ \overline{T} $ deformation. Specializing to integrable supersymmetric seed theories, such as $ \mathcal{N} $ = (2 , 2) Landau-Ginzburg models, we use the thermodynamic Bethe ansatz to study the S-matrices and ground state energies. From both an S-matrix perspective and Melzer’s folding prescription, we show that the deformed ground state energy obeys the inviscid Burgers’ equation. Finally, we show that several indices independent of D -term perturbations including the Witten index, Cecotti-Fendley-Intriligator-Vafa index and elliptic genus do not flow under the T $ \overline{T} $ deformation.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗