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DOE OSTI2025

Linear Dichroism of the Optical Properties of SnS and SnSe Van der Waals Crystals

Abstract Tin monochalcogenides SnS and SnSe, belonging to a family of Van der Waals crystals isoelectronic to black phosphorus, are known as environmentally friendly materials promising for thermoelectric conversion applications. However, they exhibit other desired functionalities, such as intrinsic linear dichroism of the optical and electronic properties originating from strongly anisotropic orthorhombic crystal structures. This property makes them perfect candidates for polarization‐sensitive photodetectors working in near‐infrared spectral range. A comprehensive study of the SnS and SnSe crystals is presented, performed by means of optical spectroscopy and photoemission spectroscopy, supported by ab initio calculations. The studies reveal the high sensitivity of the optical response of both materials to the incident light polarization, which is interpreted in terms of the electronic band dispersion and orbital composition of the electronic bands, dictating the selection rules. From the photoemission investigation the ionization potential, electron affinity and work function are determined, which are parameters crucial for the design of devices based on semiconductor heterostructures.

Chemistry↗

DOE OSTI2020

Sensitivity and Uncertainty Analysis of Generator Failures under Extreme Temperature Scenarios in Power Systems

This report summarizes work done under the Verification, Validation, and Uncertainty Quantification (VVUQ) thrust area of the North American Energy Resilience Model (NAERM) Program. The specific task of interest described in this report is focused on sensitivity analysis of scenarios involving failures of both wind turbines and thermal generators under extreme cold-weather temperature conditions as would be observed in a Polar Vortex event.

17 WIND ENERGY↗

NASA NTRS1994

The Fraternal Twins of Quartet O4(+)

Eleven stationary geometries of quartet O4(+) have been studied by ab initio methods. The geometries were optimized at the Complete Active Space Self-Consistent Field (CASSCF) level of theory and the energies were calculated by the multiconfigurational second order pertubation method (CASPT2), using Double-Zeta Plus polarization (DZP), Triple-Zeta Plus Double Polarization (TZ2P), average Atomic Natural Orbital (ANO) (5s4p2d) and average ANO (6s5p3d2f) basis sets. The rectangular and trans-planar structures are found to be the most stable, with an energy barrier to conversion between the two at the threshold of dissociation. Both have a delocalized hole and are stable relative to separated 02 and 02(+)by 11.0 and 11.5 kcal/mol for the rectangular and the 2 trans-planar structure, respectively, compared with the experimentally deduced energy in the range of 9.2 to 10.8 kcal/mol. The adiabatic ionization potentials of 04 and 02 are computed to be 11.67 and 12.21 eV, while experimental values are 11.66 and 12.07 eV, respectively. The vibrational frequencies have been computed for all degrees of freedom at the CASSCF level of theory. Symmetry breaking is found to be a particular problem in the computation of the antisymmetric stretch frequency for the delocalized structures at the CASSCF level of theory. Attempts to rectify these problems using the restricted active space self-consistent field (RASSCF) method leads to additional difficulties, but further analysis yields insight into the symmetry breaking and problems with earlier calculations. Finally, a nonorthogonal configuration interaction (CI) calculation based on the interaction of localized CASSCF wave functions using the Complete Active Space State Interation (CASSI) method leads to a balanced treatment of the antisymmetric stretch which is free from symmetry breaking. The study explains the four most prominent absorption frequencies observed in the partially unassigned IR spectrum of O4(+) isolated in solid neon as the antisymmetric OO stretch, and the combination band of the symmetric and antisymmetric 00 stretch of both the rectangular and trans-planar structures.

Lindh, Roland↗

NASA NTRS2004

A Gravity Analysis of the Subsurface Structure of the Utopia Impact Basin

The large, shallow, circular depression in Utopia Planitia has been identified as a huge impact basin, based on both geological evidence and detailed analysis of MOLA topography. Its diameter (approximately 3000 km) is equivalent to that of the Hellas basin, as is its inferred age (early Noachian). However, there the similarity ends. Their appearance, both surficially and geophysically, are virtually polar opposites. Whereas Hellas is extremely deep with rough terrain and large slopes, high-precision MOLA measurements were required to unambiguously define the smooth, shallow, almost imperceptible bowl of the Utopia basin. Conversely, Utopia displays one of the largest (non-Tharsis-related) positive geoid anomalies on Mars, in contrast to a more subdued negative anomaly over Hellas. As these two features presumably formed roughly contemporaneously by similar mechanisms, it is reasonable to assume that they were originally quite similar, and that their differences are due largely to different paths of subsequent modification. The obvious source for these differences is in their elevations: Hellas is located in the southern highlands at a rim elevation of about 3km, whereas Utopia is in the lowlying northern plains, at an average elevation of 4 km. Thus Utopia has been in an especially gravitationally favorable position to be subjected to infilling, for example, by lava flows, sedimentation, or water. In fact, its floor was almost certainly the lowest point on the planet at one time, and it would have been the termination point for down-slope drainage from over two-thirds of Mars. Thus the nature of the material filling this basin has strong connections to the sedimentary and/or volcanic processes acting on Mars in the Noachian and Early Hesperian periods. In particular, it may be able to shed some light on amount and persistence of water on early Mars in general and in the Utopia basin in particular. In this study I will use the inferred early correspondence between Hellas and Utopia to investigate Utopia's subsurface structure.

Barnerdt, W. B.↗

NASA NTRS1977

Localized induced electric field within the magnetotail

The conversion of magnetic energy, stored within the magnetotail during the growth phase, into particle kinetic energy is studied by taking induced electric fields, due to explicit time dependence of magnetic fields, into consideration. The polarization of a plasma in the presence of such a field is discussed, and the topological difference between a polarized and an induced electric field, namely that one is irrotational and the other is not, is pointed out. A localized perturbation in neutral sheet current is also discussed.

Heikkila, W. J.↗

NASA NTRS1977

Asymmetric photolysis of /RS/-leucine with circularly polarized ultraviolet light

(RS)-leucine in 0.1 M HCl solution has been subjected to photolysis with 212.8-nm right (R-) and left circularly polarized light (LCPL) obtained from a laser source. RCPL preferentially photolyzed the (R)-leucine component and LCPL the (S)-leucine component of the RS substrate. The enantiomeric excess produced were 1.98% for the 59% conversion with RCPL and 2.50% for the 75% conversion with LCPL. These 'equal and opposite' effects represent the second highest enantiomeric enrichments yet reported for an asymmetric photolysis and the first ever reported for a prebiotically important substrate - an amino acid. Implications regarding the origin of optical activity are briefly discussed.

Flores, J. J.↗

NASA NTRS1983

The association of energetic particles and shocks in the heliosphere

The observational and theoretical work on heliospheric shocks and cosmic rays in the recent past is surveyed. The data have come mainly from spacecraft in the regions from 0.3-25 AU, and include detection of particles and plasma waves upstream of the earth's bow shock. The theory of shock acceleration is reviewed, together with analytical models of energetic particle enhancement in association with shocks or shocks within the heliosphere. It has been determined that shocks in the heliosphere are associated with energetic suprathermal particles, which are conversely all associated with shocks. Solar cosmic rays and other anomalous components are therefore accelerated by shocks, a factor that is significant for studies of the acceleration mechanisms for galactic cosmic rays. The Solar Polar Mission will provide data on all solar latitudes, and the ISEE-3 spacecraft will continue to gather information on shock accelerated ions in travelling interplanetary shock waves.

Lee, M. A.↗

NASA NTRS1985

A negative ion model in the lower stratosphere

There are a number of problems in the electricity of the stratosphere at middle latitudes; e.g., the positive relation between the seasonal variations of negative polar conductivity and that of ozone density, the observed dependence of the daytime variation of conductivity on the solar zenith angle, and the interaction between the ions and aerosols, particularly the processes of the conversion from negative ions to the sulfate aerosols; e.g., ion-nucleation and the growth through multi-ion complexes. As a basic tool for investigating these problems, a negative ion chemical model was constructed in the altitude region of 15 to 30 km. Recently, the success of in situ mass analysis of stratospheric ions has revealed the nature of the most abundant ions in the stratosphere. Further, the height variations of negative ion composition between 15 and 34 km were obtained with the balloon-borne mass spectrometer by another researcher. A comparison of the calculated result with the observed result is given.

Kawamoto, H.↗

DOE OSTI2021

Photocurrent in carbon nanotube bundle: Graded Seebeck coefficient phenomenon

Here, polarized photovoltage of a suspended aligned carbon nanotube (CNT) bundle under uniform optical irradiation is discovered without additional structural modification or bias voltage. Such a phenomenon is very surprising considering the metallic behavior of the overall bundle and zero temperature difference between ends. The photovoltage characteristic time is found similar to the thermal response time under step Joule heating and implies a relation to the thermal behavior of the CNT bundle. A similar thermoelectric voltage is also observed during step Joule heating. Localized laser heating and scanning along the axial direction of the bundle uncovers a linear spatial variation of the local Seebeck coefficient. The Seebeck coefficient linearly decreases from root to tip of the CNT bundle with a rate of a few - µV∙K –1 ·mm –1 . Deep investigation in both the microscopic and macroscopic structures of the CNT bundle reveals that the local alignment of CNT assemblies rather than the minor defects in individual CNTs brings about this linear distribution of Seebeck coefficient in space. The finding presents a new way for direct photon-to-electric energy conversion via Seebeck coefficient grading in CNT structures.

42 ENGINEERING↗

DOE OSTI2021

A Nickel-Decorated Carbon Flower/Sulfur Cathode for Lean-Electrolyte Lithium–Sulfur Batteries

Lithium–sulfur (Li–S) batteries involve a reversible conversion reaction between sulfur and lithium sulfide (Li 2 S) via a series of soluble lithium polysulfide intermediates (LiPSs), enabling a high theoretical specific capacity of 1675 mAh g –1 . However, this process exhibits large polarization and low sulfur utilization and suffers critical capacity fade. The primary approach to tackle the problem has so far been to infiltrate sulfur into nanostructured carbon. Furthermore, most studies using porous carbon as host materials have tested with high electrolyte to sulfur ratios (E/S) (generally > 15 µL mg –1 ) that compromise the cell-level energy density. Here, a flower-shaped porous carbon structure with nickel nanoparticles that can address the problems discussed above is designed. First, the 3D flower-shaped carbon structure enables short ionic transport lengths. Second, the small pore diameters <10 nm and high specific surface areas > 3300 m 2 g –1 with sufficient pore volume are ideal for charging performance for low E/S ratios. Finally, Ni nanoparticles are employed onto the flower-shaped network to improve the reaction kinetics. Collectively, it is successfully demonstrated that the batteries with a high mass loading of 5 mg cm –2 and a 5 µL mg –1 E/S ratio can retain cycle retention of 70% after 150 cycles.

25 ENERGY STORAGE↗

DOE OSTI2021

Toroidal polar topology in strained ferroelectric polymer

Polar topological texture has become an emerging research field for exotic phenomena and potential applications in reconfigurable electronic devices. Here, we report toroidal topological texture self-organized in a ferroelectric polymer, poly(vinylidene fluoride-ran-trifluoroethylene) [P(VDF-TrFE)], that exhibits concentric topology with anticoupled chiral domains. The interplay among the elastic, electric, and gradient energies results in continuous rotation and toroidal assembly of the polarization perpendicular to polymer chains, whereas relaxor behavior is induced along polymer chains. Such toroidal polar topology gives rise to periodic absorption of polarized far-infrared (FIR) waves, enabling the manipulation of the terahertz wave on a mesoscopic scale. Our observations should inform design principles for flexible ferroic materials toward complex topologies and provide opportunities for multistimuli conversions in flexible electronics.

36 MATERIALS SCIENCE↗

DOE OSTI2024

Systems for Transducing Entanglement Between Photons and Electron Spins

The transfer of quantum properties and entanglement between photons and matter (transduction) is a major challenge in QIS, especially with regard to networking quantum information processing. In order to overcome this challenge, it is important to know how non-classical light (single or entangled photons) interacts with matter. This project specifically addresses fundamental questions about the interaction of single and entangled photons with molecules and nanostructures to produce electrons with prescribed spin polarizations and pairs of electrons with entangled spins, thus resulting in transduction by addressing two major objectives: (2) In Objective 1, we will investigate the formation of polarization-encoded radical (spin qubit) pairs and molecular triplet states photoexcited by single quantum emitter light sources. (2) In Objective 2, we will demonstrate the use of two entangled photons, generated by spontaneous parametric down conversion (SPDC) or by the coherent biexcitonic states of perovskite NPLs, to produce two entangled radical (spin qubit) pairs or molecular triplet states.

74 ATOMIC AND MOLECULAR PHYSICS↗

NASA NTRS1985

Prism-coupled light emission from tunnel junctions

Completely p-polarized light emission has been observed from smooth Al-AlO(x)-Au tunnel junctions placed on a prism coupler. The angle and polarization dependence demonstrate unambiguously that the emitted light is radiated by the fast-mode surface plasmon polariton. The emission spectra suggest that the dominant process for the excitation of the fast mode is through conversion of the slow mode to the fast mode mediated by residual roughness on the junction surface.

Ushioda, S.↗

NASA NTRS1987

Theoretical study of the high-latitude ionosphere's response to multicell convection patterns

A time-dependent three-dimensional model of the high-latitude ionosphere is used to study the characteristic ionospheric signatures associated with two-, three-, and four-cell plasma convection patterns. It is found that, for two-cell convection, the antisunward flow of plasma from the dayside into the polar cap acts to maintain the densities in this region in winter. For four-cell convection, the two additional convection cells in the polar cap are in darkness most of the time, and the resulting O(+) decay acts to produce twin polar holes that are separated by a sun-aligned ridge of enhanced ionization due to theta-auroral precipitation. For three-cell convection, only one polar hole forms in the total electron density, and an additional O(+) depletion region develops near noon. In this region there are strong electric fields, high ion temperatures, and an enhanced rate of O(+) - NO(+) conversion.

Sojka, J. J.↗

NASA NTRS1994

Measurements of stratospheric odd nitrogen at Arrival Heights, Antarctica, in 1991

An FTIR spectrometer was installed at Arrival Heights, Antarctica (78 deg S, 167 deg E) in February 1991 to measure the evolution of stratospheric HNO3 during the year. In particular, it was the intention to make the first observations of HNO3 trends during autumn, concurrently with ongoing measurements of column NO2 made with a grating spectrometer. The time-series of NO2 in the Antarctic shows a rapid decline in the column amount during autumn, and a slow recovery in spring, as the photochemical conditions move the species to and from higher storage reservoirs. The new nitric acid data show for the first time that during autumn the vertical column increases from approximately 1.9 x 10(exp 16) molecule cm(exp -2) at day 30 to approximately 3.1 x 10(exp 16) molecule cm(exp -2) by day 100. When the sun returns in spring, it is found that the column amount has fallen to about half the value at the end of autumn. Spring amounts are variable, but as found in the data from previous years remain low inside the vortex. The autumn increase is attributed to the heterogeneous conversion of N2O5 to gas-phase HNO3 on background aerosols. Low nitric acid column amounts at the start of spring suggest that the HNO3 has moved from the gas to the condensed phase on polar stratospheric clouds with the advent of low temperatures during the polar night.

Keys, J. Gordon↗

NASA NTRS2000

Development of a Two Dimensional Synthetic Aperture Radiometer at L-Band

A radiometer that uses aperture synthesis in two dimensions is being built as part of research under NASA's Instrument Incubator Program. The instrument development team consists of engineers at the Goddard Space Flight Center, the University of Massachusetts and Quadrant Engineering. This will be an aircraft instrument operating at L-band which builds on the heritage of ESTAR. The choice of L-band was made because the problem of achieving adequate resolution in space is most critical at this wavelength and because a polarimetric, conical scanning airborne radiometer for future experiments to validate soil moisture and ocean salinity retrieval algorithms is not currently available. The instrument will be designed to fly on the NASA P-3 aircraft in a nadir pointing mode, although other options are possible. The antenna will consist of an array of modules arranged in a rectangular grid. Each module will be comprised of a printed circuit dual-polarized patch and integrated receiver. The distribution of modules within the rectangular array will be adjustable so that several different imaging configurations (e.g. "+","Y", "T") can be employed. The integrated receiver will provide amplification and conversion to IF. The IF signal will be routed to a processor where the required correlations performed. The I and Q channels will be created digitally and the correlations will be done digitally in this processor. The digitization will be done with sufficient bits to study the effects of quantization on radiometer performance. A computer/controller will store the data for conversion to an image and will also perform temperature control and other data interfacing and housekeeping tasks. The instrument is currently in the bread boarding phase of development. A design of the critical components has been completed and hardware is being assembled to test the individual elements. It is expected that a complete 2-channel correlator will be tested by the summer of 2000 and that the complete instrument will be ready for flight tests the following summer (2001).

LeVine, D. M.↗

NASA NTRS2000

Development of a Two Dimensional Synthetic Aperture Radiometer at L-Band

A radiometer that uses aperture synthesis in two dimensions is being built as part of research under NASA's Instrument Incubator Program. The instrument development team consists of engineers at the Goddard Space Flight Center, the University of Massachusetts and Quadrant Engineering. This will be an aircraft instrument operating at L-band which builds on the heritage of Electronically Steered Thinned Array Radiometer (ESTAR). This instrument is a next step in the development of aperture synthesis (STAR technology) to meet the goal of a future mission to monitor soil moisture globally from space. The instrument will be designed to fly on the NASA P-3 aircraft in a nadir pointing mode, although other options are possible. The antenna will consist of an array of modules in a rectangular grid. Each module will be comprised of a printed circuit dual-polarized patch and integrated receiver. The distribution of modules within the rectangular array will be adjustable so that several different imaging configurations (e.g. '+', 'Y', 'T') can be employed. The integrated receiver will provide amplification and conversion to infrared (IF). The IF signal will be routed to a processor where the required correlations performed. The I and Q channels will be created digitally and the correlations will be done digitally in this processor. The digitization will be done with sufficient bits to study the effects of quantization on radiometer performance. A computer/controller will store the data for conversion to an image and will also perform temperature control and other data interfacing and housekeeping tasks. The design of critical components has been completed and hardware is being assembled to test the individual elements. It is expected that a complete two-channel correlator will be tested by the end of 2000 and that the complete instrument will be ready for flight tests the following summer (2001).

LeVine, D. M.↗

NASA NTRS2022

Variability of the Reconnection Guide Field in Solar Flares

Solar ﬂares may be the best-known examples of the explosive conversion of magnetic energy into bulk motion, plasma heating, and particle acceleration via magnetic re-connection. The energy source for all ﬂares is the highly sheared magnetic ﬁeld of a ﬁlament channel above a polarity inversion line (PIL). During the ﬂare, this shear ﬁeld becomes the so-called reconnection guide ﬁeld (i.e., the non-reconnecting component), which has been shown to play a major role in determining key properties of the recon-nection including the eﬃciency of particle acceleration. We present new high-resolution, three-dimensional, magnetohydrodynamics simulations that reveal the detailed evolution of the magnetic shear/guide ﬁeld throughout an eruptive ﬂare. The magnetic shear evolves in three distinct phases: shear ﬁrst builds up in a narrow region about the PIL, then expands outward to form a thin vertical current sheet, and ﬁnally is transferred by ﬂare reconnection into an arcade of sheared ﬂare loops and an erupting ﬂux rope. We demonstrate how the guide ﬁeld may be inferred from observations of the sheared ﬂare loops. Our results indicate that initially the guide ﬁeld is larger by about a factor of 5 than the reconnecting component, but it weakens by more than an order of magnitude over the course of the ﬂare. Instantaneously, the guide ﬁeld also varies spatially over a similar range along the three-dimensional current sheet. We discuss the implications of the remarkable variability of the guide ﬁeld for the timing and localization of eﬃcient particle acceleration in ﬂares.

Solar magnetic reconnection↗