Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “TRIPLETS”

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 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

The Effect of Quantum-Mechanical Interference on Precise Measurements of the n = 2 Triplet P Fine Structure of Helium

For many decades, improvements in both theory and experiment of the fine structure of the n = 2 triplet P levels of helium have allowed for an increasingly precise determination of the fine-structure constant. Recently, it has been observed that quantum-mechanical interference between neighboring resonances can cause significant shifts, even if such neighboring resonances are separated by thousands of natural widths. The shifts depend in detail on the experimental method used for the measurement, as well as the specific experimental parameters employed. Here, we review how these shifts apply for the most precise measurements of the helium 2{sup 3}P fine-structure intervals.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Global triplet potential energy surfaces for the N{sub 2}(X{sup 1}Σ) + O({sup 3}P) → NO(X{sup 2}Π) + N({sup 4}S) reaction

This work presents two global triplet potential energy surfaces (PESs) for the high-energy reaction N{sub 2}(X{sup 1}Σ) + O({sup 3}P) → NO(X{sup 2}Π) + N({sup 4}S)—in particular, for the lowest energy {sup 3}A′ and {sup 3}A″ PESs. In order to obtain the energies needed for fitting analytic surfaces, we carried out multireference configuration interaction (MRCI) calculations based on wave functions obtained from state-averaged complete active space self-consistent field calculations for 2280 geometries for the three lowest {sup 3}A″ states and for 2298 geometries for the three lowest {sup 3}A′ states. The lowest-energy {sup 3}A′ and {sup 3}A″ states at each of these geometries were then improved by applying the dynamically scaled external correlation (DSEC) method to all MRCI points, and the resulting DSEC energies were used for construction of the ground-state PES for each symmetry. The many-body component of the DSEC energies for the three-dimensional {sup 3}A′ and {sup 3}A″ PESs was then least-squares fitted in terms of permutationally invariant polynomials in mixed exponential–Gaussian bond order variables. The global and local minima as well as the transition structures of both the {sup 3}A′ and the {sup 3}A″ analytic PES were explored. In agreement with previous work, we find that the reverse reaction is barrierless on the {sup 3}A″ surface along the minimum energy pathway. However, we have explored several new local minima and transition structures on the {sup 3}A′ PES. Furthermore, based on the newly found minima and transition structures, two independent reaction mechanisms have been illustrated for the reaction path on the {sup 3}A′ PES. The analytic surfaces may be used for dynamics calculations of electronically adiabatic reactive scattering and energy transfer.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Potential energy surface of triplet N{sub 2}O{sub 2}

We present a global ground-state triplet potential energy surface for the N{sub 2}O{sub 2} system that is suitable for treating high-energy vibrational-rotational energy transfer and collision-induced dissociation. The surface is based on multi-state complete-active-space second-order perturbation theory/minimally augmented correlation-consistent polarized valence triple-zeta electronic structure calculations plus dynamically scaled external correlation. In the multireference calculations, the active space has 14 electrons in 12 orbitals. The calculations cover nine arrangements corresponding to dissociative diatom-diatom collisions of N{sub 2}, O{sub 2}, and nitric oxide (NO), the interaction of a triatomic molecule (N{sub 2}O and NO{sub 2}) with the fourth atom, and the interaction of a diatomic molecule with a single atom (i.e., the triatomic subsystems). The global ground-state potential energy surface was obtained by fitting the many-body interaction to 54 889 electronic structure data points with a fitting function that is a permutationally invariant polynomial in terms of bond-order functions of the six interatomic distances.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Time sequence spectroscopy of AW UMa. The 518 nm Mg I triplet region analyzed with broadening functions

High-resolution spectroscopic observations of AW UMa, obtained on three consecutive nights with a median time resolution of 2.1 minutes, have been analyzed using the broadening function method in the spectral window of 22.75 nm around the 518 nm Mg i triplet region. Doppler images of the system reveal the presence of vigorous mass motions within the binary system; their presence puts into question the solid-body rotation assumption of the contact binary model. AW UMa appears to be a very tight, semi-detached binary; the mass transfer takes place from the more massive to the less massive component. The primary, a fast-rotating star with Vsini=181.4±2.5 km s{sup −1}, is covered with inhomogeneities: very slowly drifting spots and a dense network of ripples more closely participating in its rotation. The spectral lines of the primary show an additional broadening component (called the “pedestal”) that originates either in the equatorial regions, which rotate faster than the rest of the star by about 50 km s{sup −1}, or in an external disk-like structure. The secondary component appears to be smaller than predicted by the contact model. The radial velocity field around the secondary is dominated by accretion of matter transferred from (and possibly partly returned to) the primary component. The parameters of the binary are Asini=2.73±0.11 R{sub ⊙} and M{sub 1}sin{sup 3}i=1.29±0.15 M{sub ⊙}, M{sub 2}sin{sup 3}i=0.128±0.016 M{sub ⊙}. The mass ratio, q{sub sp}=M{sub 2}/M{sub 1}=0.099±0.003, while still the most uncertain among the spectroscopic elements, is substantially different from the previous numerous and mutually consistent photometric investigations which were based on the contact model. It should be studied why photometry and spectroscopy give such discrepant results and whether AW UMa is an unusual object or if only very high-quality spectroscopy can reveal the true nature of W UMa-type binaries.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

WIYN Open Cluster Study. LXIII. Abundances in the super-metal-rich open cluster NGC 6253 from hydra spectroscopy of the 7774 Å oxygen triplet region

We present a spectroscopic abundance analysis of the old, super-metal-rich open cluster NGC 6253, with emphasis on its O abundance. High-dispersion, 7774 Å O i triplet region spectra of 47 stars were obtained using Hydra II on the CTIO Blanco 4 m. Radial velocity analysis confirms 39 stars consistent with single star membership, primarily at the turnoff. Thirty-six of these are included in our abundance analysis. Our differential analysis relative to the Sun yields primarily scaled-solar values, with weighted cluster averages of [O/H] = +0.440 ± 0.020, [Fe/H] = +0.445 ± 0.014, [Al/H] = +0.487 ± 0.020, [Si/H] = +0.504 ± 0.018, and [Ni/H] = +0.702 ± 0.018 (where the errors are σ{sub μ}). We discuss possible origins for the three known super-metal-rich clusters based upon their abundance patterns, Galactic locations, and space motions. The abundance patterns of NGC 6253 are very similar to those of NGC 6791 and NGC 6583. With the possible exception of oxygen, the abundances of these clusters are all close to scaled-solar, and they are similar to patterns seen in metal-rich disk dwarfs and giants. However, they also seem to differ from those of metal-rich bulge stars. We demonstrate that NGC 6253 is unusually oxygen rich (in [O/H]) for its 3.3 Gyr age. While we find [O/Fe] to be scaled-solar for NGC 6253, the more recently reported values for NGC 6791 show a large variation, from values close to scaled-solar down to values at least a factor of two below scaled-solar. We discuss the possibility that the scaled-solar [O/Fe] abundances of NGC 6253 and NGC 6791 might reflect a flattening of the Galactic [O/Fe] versus [Fe/H] relationship. This possibility may be consistent with disk star abundance data, which show an apparent “floor” at [O/Fe] ∼−0.1 for [Fe/H] > 0, and with chemical evolution model results, which may predict such a flattening due to a decrease in supernova Fe yields at super-solar-metallicities. Orbit solutions for NGC 6791 allow that it may have formed in the inner disk and was then kicked out, but the origins of the other two much younger clusters remain mysterious. We re-evaluate the age of NGC 6583 in view of the evidence that the cluster is super-metal-rich, and confirm a probable age less than 1 Gyr (best range: 500–900 Myr). We also argue that it is unlikely the cluster is more than 3 kpc away (best range: 2–3 kpc) if the apparent turnoff, main sequence, and giants are all cluster members.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

CA II TRIPLET SPECTROSCOPY OF SMALL MAGELLANIC CLOUD RED GIANTS. III. ABUNDANCES AND VELOCITIES FOR A SAMPLE OF 14 CLUSTERS

We obtained spectra of red giants in 15 Small Magellanic Cloud (SMC) clusters in the region of the Ca ii lines with FORS2 on the Very Large Telescope. We determined the mean metallicity and radial velocity with mean errors of 0.05 dex and 2.6 km s{sup −1}, respectively, from a mean of 6.5 members per cluster. One cluster (B113) was too young for a reliable metallicity determination and was excluded from the sample. We combined the sample studied here with 15 clusters previously studied by us using the same technique, and with 7 clusters whose metallicities determined by other authors are on a scale similar to ours. This compilation of 36 clusters is the largest SMC cluster sample currently available with accurate and homogeneously determined metallicities. We found a high probability that the metallicity distribution is bimodal, with potential peaks at −1.1 and −0.8 dex. Our data show no strong evidence of a metallicity gradient in the SMC clusters, somewhat at odds with recent evidence from Ca ii triplet spectra of a large sample of field stars. This may be revealing possible differences in the chemical history of clusters and field stars. Our clusters show a significant dispersion of metallicities, whatever age is considered, which could be reflecting the lack of a unique age–metallicity relation in this galaxy. None of the chemical evolution models currently available in the literature satisfactorily represents the global chemical enrichment processes of SMC clusters.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

MAGNETIC FIELD STRENGTH FLUCTUATIONS AND THE q-TRIPLET IN THE HELIOSHEATH: VOYAGER 2 OBSERVATIONS FROM 91.0 TO 94.2 AU AT LATITUDE 30 Degree-Sign S

Voyager 2 (V2) was in the heliosheath during 2010, at (91.0-94.2) AU from the Sun and at the latitudes (28. Degree-Sign 8-29. Degree-Sign 3 S) AU, observing solar wind that left the Sun during 2009, when solar activity was very low. There was no feature in B(t) associated with the changes in the plasma parameters observed near 2010.4. The CR-B relation was satisfied. The fluctuations of daily averages of B showed (1) a Gaussian distribution of B, (2) a q-Gaussian of the daily increments of B with q = 1.6, (3) a power-law correlation of B on scales from 1 to 16 days, (4) multifractal structure of B on scales from 1 to 8 days, and (5) a 1/f spectrum of B on scales from 1 to 100 days. The amplitude of the compressive microscale fluctuations of B during several hours on each day is described by the standard deviation (SD) of the 48 s averages of B during the day. Items 2, 3, and 4 determine a 'q-triplet' in the heliosheath. Large-scale fluctuations of SD show (1) a lognormal distribution of SD; (2) an average value of SD = 0.19, 20% of the average B; (3) a q-Gaussian distribution of the increments of SD with q = 1.4; (4) a power-law correlation on scales from 1 to 16 days; and (5) a 1/f spectrum on scales from 1 to 100 days. The heliosheath was in a quasi-stationary, metastable equilibrium state with well-defined structure over a wide range of scales near V2 during 2010.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

Discovery of a tidal dwarf galaxy in the Leo Triplet

We report the discovery of a dwarf galaxy in the Leo Triplet. Analysis of the neutral hydrogen distribution shows that it rotates independently of the tidal tail of NGC 3628, with a radial velocity gradient of 35-40 km s{sup –1} over approximately 13 kpc. The galaxy has an extremely high neutral gas content, accounting for a large amount of its total dynamic mass and suggesting a low amount of dark matter. It is located at the tip of the gaseous tail, which strongly suggests a tidal origin. If this is the case, it would be one of the most confident and nearest (to the Milky Way) detections of a tidal dwarf galaxy and, at the same time, the object most detached from its parent galaxy (≈140 kpc) of this type.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

Leptogenesis, radiative neutrino masses and inert Higgs triplet dark matter

We extend the standard model by three types of inert fields including Majorana fermion singlets/triplets, real Higgs singlets/triplets and leptonic Higgs doublets. In the presence of a softly broken lepton number and an exactly conserved Z{sub 2} discrete symmetry, these inert fields together can mediate a one-loop diagram for a Majorana neutrino mass generation. The heavier inert fields can decay to realize a successful leptogenesis while the lightest inert field can provide a stable dark matter candidate. As an example, we demonstrate the leptogenesis by the inert Higgs doublet decays. We also perform a systematic study on the inert Higgs triplet dark matter scenario where the interference between the gauge and Higgs portal interactions can significantly affect the dark matter properties.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

Fluctuation-induced odd-frequency spin-triplet pairing in a disordered electron liquid

Here we consider a two-dimensional disordered conductor in the regime when the superconducting phase is destroyed by the magnetic field. We analyze a combination of fluctuations of different origin which results in an effective interaction amplitude suitable for a spontaneous s-wave odd-frequency pairing instability. We observe that the end point of the superconductivity is a quantum critical point separating the conventional superconducting phase from a state with the odd-frequency spin-triplet pairing instability. We speculate that this could shed light on a rather mysterious insulating state observed in strongly disordered superconducting films in a broad region of the magnetic fields.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Spin-triplet supercurrent in Josephson junctions containing a synthetic antiferromagnet with perpendicular magnetic anisotropy

In this paper, we present measurements of Josephson junctions containing three magnetic layers with noncollinear magnetizations. The junctions are of the form S / F ' / N / F / N / F " / S , where S is superconducting Nb, F ' is either a thin Ni or Permalloy layer with in-plane magnetization, N is the normal metal Cu, F is a synthetic antiferromagnet with magnetization perpendicular to the plane, composed of Pd/Co multilayers on either side of a thin Ru spacer, and F " is a thin Ni layer with in-plane magnetization. The supercurrent in these junctions decays more slowly as a function of the F -layer thickness than for similar spin-singlet junctions not containing the F ' and F " layers. The slower decay is the prime signature that the supercurrent in the central part of these junctions is carried by spin-triplet pairs. Finally, the junctions containing F ' = Permalloy are suitable for future experiments where either the amplitude of the critical current or the ground-state phase difference across the junction is controlled by changing the relative orientations of the magnetizations of the F ' and F " layers.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2013

Analysis of triplet production by a circularly polarized photon at high energies

The possibility in principle of determining the circular polarization of a high-energy photon by measuring the created electron polarization in the process of triplet photoproduction {gamma} + e{sup -} {yields} e{sup +}e{sup -} + e{sup -} is investigated. The respective event number, which depends on polarization states of the photon and the created electron, does not decrease as the photon energy increases, and this circumstance can ensure the high efficiency in such experiments. We study different double and single distributions of the created electron (or positron), which allow probing the photon circular polarization and measuring its magnitude (the Stokes parameter {xi}{sub 2}) using the technique of Sudakov variables. Some experimental setups with different rules for event selection are studied and the corresponding numerical estimations are presented.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

Photoproduction of Triplets on Free Electrons and the Search for the Dark Photon

We have investigated the photoproduction of triplets on free electrons, γe{sup –} → e{sup +}e{sup –}e{sup –}, in which dark photon A′ can be formed as an intermediate state with subsequent decay into an e{sup +}e{sup –} pair. This effect appears as a result of the so-called kinetic mixing and is characterized by the small parameter describing the intensity of the interaction of the dark photon with charged Standard Model (SM) particles in terms of electric charge e. The search for a manifestation of A′ in this process is advantageous since the background to the A′ signal is purely electrodynamic and, hence, can be calculated with the required accuracy. We calculate this background taking into account the identity of final electrons. As regards A′, its contribution is taken into account only in Compton-type diagrams (of virtual Compton scattering) in which a virtual dark photon is a time-like particle and its propagator has the form of a Breit–Wigner resonance. It is only in the vicinity of resonance that A′ can be manifested. We calculate the invariant mass distribution of both e{sup +}e{sup –} pairs formed in the process and analyze the kinematic region in which relatively small squares of momenta transferred from the target electron to the formed electrons are excluded. In these conditions, the contribution to the differential cross section from Compton-type diagrams is not suppressed relative to the contribution of the remaining (Borsellino) diagrams. A number of limitations on parameter depending on the dark photon mass and the statistics (number) of events are obtained for a special method of gathering events in which the invariant mass of one e{sup +}e{sup –} pair remains fixed and of the other pair is scanned.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

Evolution of Triplet Paramagnetic Centers in Diamonds Obtained by Sintering of Detonation Nanodiamonds at High Pressure and Temperature

The electron paramagnetic resonance (EPR) spectra of triplet centers in detonation nanodiamonds (DNDs) and diamond single crystals of submicrometer size, synthesized from those DNDs at high pressures and temperatures, are studied. In the EPR spectra of DNDs, signals from negatively charged nitrogen- vacancy centers (NV)/sup(-) with a g factor of g{sub 1} = 4.24 and multivacancies with g{sub 2} = 4.00 are observed. The signals from (NV)/sup(-) centers disappear in the spectra of diamond single crystals, and a quintet signal with g = 4.00 is detected at the position of the signal from multivacancies. Analysis of the shape and position of the quintet’ lines showed that this ESR signal is due to the pairs of nitrogen substitution centers in diamond, separated from each other by distances not exceeding 0.7 nm, between which a strong exchange interaction takes place. A comparison of the experimental data and the simulation results allows determining the spin-Hamiltonian parameters of the exchange-coupled pairs of paramagnetic impurity nitrogen atoms.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2016

NON-LTE INVERSIONS OF THE Mg ii h and k AND UV TRIPLET LINES

The Mg ii h and k lines are powerful diagnostics for studying the solar chromosphere. They have become particularly popular with the launch of the Interface Region Imaging Spectrograph ( IRIS ) satellite, and a number of studies that include these lines have lead to great progress in understanding chromospheric heating, in many cases thanks to the support from 3D MHD simulations. In this study, we utilize another approach to analyze observations: non-LTE inversions of the Mg ii h and k and UV triplet lines including the effects of partial redistribution. Our inversion code attempts to construct a model atmosphere that is compatible with the observed spectra. We have assessed the capabilities and limitations of the inversions using the FALC atmosphere and a snapshot from a 3D radiation-MHD simulation. We find that Mg ii h and k allow reconstructing a model atmosphere from the middle photosphere to the transition region. We have also explored the capabilities of a multi-line/multi-atom setup, including the Mg ii h and k, the Ca ii 854.2 nm, and the Fe i 630.25 lines to recover the full stratification of physical parameters, including the magnetic field vector, from the photosphere to the chromosphere. Finally, we present the first inversions of observed IRIS spectra from quiet-Sun, plage, and sunspot, with very promising results.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

Correlation of Broad Absorption Band with Small Singlet‐Triplet Energy Gap in Organic Photovoltaics

Abstract Organic photovoltaics (OPV) are one of the most effective ways to harvest renewable solar energy, with the power conversion efficiency (PCE) of the devices soaring above 19 % when processed with halogenated solvents. The superior photocurrent of OPV over other emerging photovoltaics offers more opportunities to further improve the efficiency. Tailoring the absorption band of photoactive materials is an effective way to further enhance OPV photocurrent. However, the field has mostly been focusing on improving the near‐infrared region photo‐response, with the absorption shoulders in short‐wavelength region (SWR) usually being neglected. Herein, by developing a series of non‐fullerene acceptors (NFAs) with varied side‐group conjugations, we observe an enhanced SWR absorption band with increased side‐group conjugation length. The underpinning factors of how molecular structures and geometries improve SWR absorption are clearly elucidated through theoretical modelling and crystallography. Moreover, a clear relationship between the enhanced SWR absorption and reduced singlet‐triplet energy gap is established, both of which are favorable for the OPV performance and can be tailored by rational structure design of NFAs. Finally, the rationally designed NFA, BO‐TTBr, affords a decent PCE of 18.5 % when processed with a non‐halogenated green solvent.

Chemistry↗