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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 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Quantum-amplified global-phase spectroscopy on an optical clock transition

Optical lattice clocks are at the forefront of precision metrology, operating near a standard quantum limit set by quantum noise. Harnessing quantum entanglement offers a promising route to surpass this limit; however, there are practical difficulties in terms of scalability and measurement resolution requirements. Here we adapt the holonomic quantum gate concept to develop a new Rabi-type ‘global-phase spectroscopy’ that uses the detuning-sensitive global Aharonov–Anandan phase19. With this approach, we can demonstrate quantum-amplified time-reversal spectroscopy on an optical clock transition that achieves directly measured 2.4(7) dB metrological gain and 4.0(8) dB improvement in laser noise sensitivity beyond the standard quantum limit. To this end, we introduce rotary echo to protect the dynamics from inhomogeneities in light–atom coupling and implement a laser-noise-cancelling differential measurement through symmetric phase encoding in two nuclear spin states. Our technique is not limited by measurement resolution, scales easily because of the global nature of entangling interaction and exhibits high resilience to typical experimental imperfections. As a result, we expect it to be broadly applicable to next-generation atomic clocks and other quantum sensors approaching the fundamental quantum precision limits.

Zaporski, Leon [Massachusetts Institute of Technol↗
DOE OSTI2025

Two-dimensional ring polymer molecular dynamics determination of the MnO + + H 2 /D 2 reaction rates on a Δ-machine learned potential energy surface

In this work, we investigate the impact of nuclear quantum effects in the kinetics of the MnO + + H 2 reaction, a prototypical system for gas-phase H 2 activation by transition metal oxide ions. The DFT based potential energy surfaces (PESs) for the lowest-lying quintet and septet spin states reported in our previous work are improved by 2953 newly calculated CCSD(T)/AVDZ points using a delta-machine learning (Δ-ML) method. To examine nuclear quantum effects, the rate coefficients are computed using ring-polymer molecular dynamics (RPMD). Due to the mechanistic complexity of the reaction, two reaction coordinates are necessary to map out the free-energy surface and an extended RPMD rate theory is developed. The calculated RPMD rate coefficients on the new PES are in better agreement with experimental data. The calculated kinetic isotope effects (KIEs) range from 1.6 to 1.8, also in good agreement with the experimental values. Additionally, the converged RPMD rate coefficients are 2.3 to 3.1 times higher than their classical counterparts across the studied temperature range, suggesting the presence of moderate nuclear quantum effects in this reaction.

Liu, Yang [University of New Mexico, Albuquerque, ↗
DOE OSTI2025

Designing molecular qubits: computational insights into first-row and group 6 transition metal complexes

In the realm of optically addressable qubits, a previously synthesized and characterized Cr( IV ) pseudo-tetrahedral complex, featuring four strongly donating ligands surrounding the chromium center, has demonstrated potential as a qubit candidate. This study proposes analogs of this complex through a metal substitution strategy, extending the investigation to different complexes based on metal centers selected from first-row and Group 6 transition metals. Computational modeling based on multiconfigurational methods CASPT2 and MC-PDFT was utilized to calculate energy gaps between ground and excited electronic spin states, and zero-field splitting parameters. Simulations were applied to each equilibrium geometry and related deformations based on vibrational modes. All results align with previous experimental findings, but also show that qubits based on V and Ti centers could be more electronically stable than the Cr one, suggesting a lower electronic features dependency from their related geometry. In some cases geometrical deformations provide changes in relative energy gaps between triplet and singlet excited state, that could potentially swap, offering a different initialization process, and some inspiration for ligand design based on such deformations. Additionally, this study identifies an unsynthesized Ti( II ) compound as a promising candidate for molecular qubits. This finding highlights the role of computational multireference methods in the rational design of qubit systems.

Sauza-de la Vega, Arturo [Univ. of Chicago, IL (Un↗
DOE OSTI2025

Wide-field microwave magnetic field imaging with nitrogen-vacancy centers in diamond

Non-invasive imaging of microwave (MW) magnetic fields with microscale lateral resolution is pivotal for various applications, such as MW technologies and integrated circuit failure analysis. Diamond nitrogen-vacancy (NV) center magnetometry has emerged as an ideal tool, offering micrometer-scale resolution, millimeter-scale field of view, high sensitivity, and non-invasive imaging compatible with diverse samples. However, up until now, it has been predominantly used for imaging of static or low-frequency magnetic fields or, concerning MW field imaging, to directly characterize the same microwave device used to drive the NV spin transitions. In this work, we leverage an NV center ensemble in diamond for wide-field imaging of MW magnetic fields generated by a test device employing a differential measurement protocol. The microscope is equipped with a MW loop to induce Rabi oscillations between NV spin states, and the MW field from the device-under-test is measured through local deviations in the Rabi frequency. This differential protocol yields magnetic field maps of a 2.57 GHz MW field with a sensitivity of ∼9 μT Hz −1/2 for a total measurement duration of T=357 s, covering a 340 × 340 μm 2 field of view with a micrometer-scale spatial resolution and a device-under-test input power dynamic range of 30 dB. This work demonstrates a novel NV magnetometry protocol, based on differential Rabi frequency measurement, that extends NV wide-field imaging capabilities to imaging of weak MW magnetic fields that would be difficult to measure directly through standard NV Rabi magnetometry.

crystallographic defects↗
DOE OSTI2025

Characterization of chromium impurities in β -Ga2O3

Chromium is a common transition-metal impurity that is easily incorporated during crystal growth. It is perhaps best known for giving rise to the 694.3 nm (1.786 eV) emission in Cr-doped Al2O3, exploited in ruby lasers. Chromium has also been found in monoclinic gallium oxide, a wide-bandgap semiconductor being pursued for power electronics. In this work, we thoroughly characterize the behavior of Cr in Ga2O3 through theoretical and experimental techniques. β-Ga2O3 samples are grown with the floating zone method and show evidence of a sharp photoluminescence signal, reminiscent of ruby. We calculate the energetics of formation of Cr from first principles, demonstrating that Cr preferentially incorporates as a neutral impurity on the octahedral site. Cr possesses a quartet ground-state spin and has an internal transition with a zero-phonon line near 1.8 eV. By comparing the calculated and experimentally measured luminescence lineshape function, we elucidate the role of coupling to phonons and uncover features beyond the Franck–Condon approximation. The combination of strong emission with a small Huang–Rhys factor of 0.05 and a technologically relevant host material renders Cr in Ga2O3 attractive as a quantum defect.

Turiansky, Mark E. (ORCID:0000000291543582)↗
DOE OSTI2024

Layer-by-layer assembly of a [Fe-(pyrazine){Pd(CN) 4 }] spin crossover thin film

Abstract [Fe-(pyrazine){Pd(CN) 4 }] (pyrazine = pz) thin films were fabricated using a layer-by-layer assembly approach, a method known to be tunable, versatile, and scalable, since thin films are better-suited for industrial applications. In this study, [Fe-(pz){Pd(CN) 4 }] powder was synthesized, and the results obtained from a vibrating sample magnetometer verified the presence of an abrupt hysteresis loop with widths of 45 K centered around 300 K, indicating good cooperativity. Super conducting quantum interference device magnetometry results indicated a slow spin transition with temperature but with evidence of hysteresis for thin film samples. X-ray absorption analysis provided further support of the spin crossover behavior but differs from the magnetometry because the spin state transition at the surface differs from the bulk of the thin film. X-ray photoelectron spectroscopy provided some insight into issues with the film deposition process and multiplex fitting was used to further support the claim that the surface of the film is different than the bulk of the film.

McElveen, Kayleigh A. (ORCID:0000000210302913)↗
DOE OSTI2026

First Observation of Multiphonon 𝛾-Vibrations in an Odd-Odd Nuclear System

Here, the identification of the first multiphonon 𝛾-vibrational bands in an odd-odd neutron-rich nucleus of the nuclear chart is presented. These high-spin structures of hard to access $^{104}_{41}\textrm{Nb}_{63}$, produced in fission, were studied by combining a spectrometer with isotopic resolution coupled to a 𝛾-ray tracking array and independently from high-fold 𝛾 coincidence measurements. Triaxial projected shell model calculations for the high-spin states are in good agreement with the measured observables for the yrast, one-phonon, and two-phonon 𝛾 bands. The possibility of an oblate shape of an isomeric state and coexistence of triaxial and oblate configurations is investigated from the decay of the 141 keV isomer. The present Letter illustrates the robustness of vibration excitations in the presence of an odd valence proton and neutron as well as the possibly coexisting shapes beyond the 𝑁 = 60 transitional region.

Wang, E. H. [Shandong Univ., Jinan (China); Vander↗
DOE OSTI2026

Nanoscale Defects as Probes of Time-Reversal Symmetry Breaking

Nanoscale defects such as nitrogen-vacancy (NV) centers can serve as sensitive and noninvasive probes of electromagnetic fields and fluctuations from materials, which in turn can be used to characterize these systems. Here we specifically discuss how NV centers can probe time-reversal symmetry breaking (TRSB) phenomena in low-dimensional electronic systems. We argue that the difference in relaxation rates Γ$_{±\hat{z}}$ of NV centers starting from 𝑚 = ±1 spin states to the ground state with 𝑚 = 0 directly probes TRSB. The effect arises from the difference in the fluctuation spectrum of left- and right-polarized electromagnetic fields emanating from such materials. In the quantum Hall setting, the NV center experiences (nearly zero) large additional contribution to its relaxation due to the presence of the material when its magnetic dipole (anti)aligns with the external field. More generally, the difference in the relaxation rates is sensitive to the imaginary part of the wave-vector-dependent Hall conductivity. We argue that this can be used to determine the Hall viscosity, which can potentially distinguish candidate fractional quantum Hall states and be used to infer the pairing angular momentum in TRSB superconductors. We compute the average relaxation rate [Γ$_{+\hat{z}}$ + Γ$_{-\hat{z}}$] near thin film superconductors and find that it exhibits a Hebel-Slichter-like enhancement below 𝑇 𝑐 . The difference Γ$_{+\hat{z}}$ −Γ$_{-\hat{z}}$ also inherits this peak but is only nonzero for 𝑇 < 𝑇 𝑐 and only if the superconductivity is chiral. We provide concrete estimates for observing this effect in stacked twisted bismuth strontium calcium copper oxide flakes.

NV centers↗
DOE OSTI2026

Hyperfine spectroscopy and laser cooling of the fermionic isotopes 47 Ti and 49 Ti

Here, we report on magneto-optical trapping of the two fermionic isotopes of atomic titanium, 47 Ti and 49 Ti . Unlike the even mass-number isotopes, which were recently laser cooled, 47 Ti and 49 Ti have nonzero nuclear spins and, consequently, their atomic levels are split by hyperfine structure. Combining and comparing theoretical calculations and atomic beam-spectroscopy measurements, we determine the hyperfine structures and isotope shifts of the 3⁢𝑑 2 ⁢4⁢𝑠 2 𝑎 3 ⁢𝐹 4 → 3⁢𝑑 2 ⁢( 3 𝑃)⁢4⁢𝑠⁢4⁢𝑝⁢( 3 𝑃 𝑜 ) 𝑦 5 ⁢𝐷$^o_4$ optical-pumping transition at optical wavelength 391 nm and the 3⁢𝑑 3 ⁢(4𝐹)⁢4⁢𝑠 𝑎 5 ⁢𝐹 5 → 3⁢𝑑 3 ⁢( 4 𝐹)⁢4⁢𝑝 𝑦 5 ⁢𝐺$^𝑜_6$ laser-cooling transition at wavelength 498 nm. With this information, we produce magneto-optical traps of both 47 Ti and 49 Ti by applying two additional tones of light to repump atoms to the maximum-spin states on the laser-cooling transition. Directly loading from the atomic flux of a titanium sublimation pump, we produce 47 Ti and 49 Ti traps with 731(190) and 1142(240) atoms, and with lifetimes of 330⁢(15) and 310⁢(8)⁢ ms, respectively.

atomic spectra↗
DOE OSTI2025

Probing soft X-ray induced photoreduction of a model Mn-complex at cryogenic conditions

Soft X-ray absorption spectroscopy of first row transition elements at their respective L -edges provides important information about the oxidation and spin states of the metal centers. However, the associated sample damage in radiation-sensitive samples substantially alters the electronic and chemical structures of redox-active metal centers. Here, we measure the soft X-ray spectrum of the model Mn III (acac) 3 complex containing a redox-active Mn III metal center in an octahedral environment with a superconducting transition-edge sensor detector. To reduce the secondary damage resulting primarily from the diffusion of radicals and electrons, the spectra are collected at 30 K and 80 K on solid samples. Starting from the first scan, we detect the contribution of X-ray induced sample damage leading to a change in the Mn II intensity. However, at low temperatures, particularly at 30 K, we do not observe a gradual increase in the radiation damage with successive scans with the X-ray beam at the same spot. At our estimated dose of 90 kGy, we find 62% of Mn III (acac) 3 is still intact at 30 K. However, at room temperature, we see a gradual increase in radiation damage with increasing numbers of scans at the same spot, which is consistent with the possibility of increased diffusion rates of secondary radicals and electrons as noted in other studies.

L-edge spectroscopy↗
NASA NTRS1973

Rotary acceleration

Rotary acceleration is found to be a manifestation of angular acceleration, and is always present during steady state spinning or tumbling, even when the angular velocity is constant. Subjective reactions and tolerances, performance, physiological effects, and pathological effects are reviewed for rotary acceleration. Thresholds for stimulation perception by angular acceleration in man are presented in tabular form.

Fraser, T. M.↗
NASA NTRS1982

Analysis of rotary balance data for the F-15 airplane including the effect of conformal fuel tanks

F-15 rotary balance data was analyzed, and the influence of control deflections, Reynolds number and airplane components, i.e., body, wing, horizontal and vertical tails, as well as conformal tanks, on the aerodynamics up to 90 degrees angle of attack are discussed. Steady state spin mode predictions using these data are presented, which show excellent correlation with spin tunnel and flight test results. Generally, the data shows damped yawing moment slopes with rotation at all angles of attack, and good control effectiveness. Differences in the rotary aerodynamics due to the addition of conformal tanks are minimal. The small differences in the region of the flat spin do, however, indicate that the resulting spin mode would be slightly flatter and faster for a conformal tank equipped airplane. The addition of conformal tanks make the airplane more departure susceptible.

Barnhart, B.↗
NASA NTRS1982

High-temperature electronics applications in space exploration

One of the most exciting applications of high-temperature electronics is related to the exploration of the planet Venus. On this planet the atmospheric temperatures range from about 170 K at elevations of 100 km to a searing 730 K near the surface. Mechanisms for exploring the atmosphere might include balloons, airplanes, surface landers, and surface-launched probes. Balloons, for example, could fly in the region from 20 (320 C at 22 bars) to 60 km (-20 C at 0.2 bar). Suitable balloon fabrics presently exclude excursions to lower altitudes; however, adequate electronic systems could survive to 325 C. Small airplanes would require more sophisticated electronics for guidance and control. Long life surface landers would most likely be developed first, as these could be used to measure long-term variations in weather. Ranging transponders would be important for ephemeris development, measurement of spin state, and studies of general relativity. Surface temperatures of 460 C and pressures of 90 bars present a challenge to the developers of such instruments. Other space applications for high-temperature electronics include transponders for the surface of Mercury, near solar drag-free orbiters, and deep atmospheric penetrators for Jupiter and Saturn. Each of these has its own particular problems with respect to instrumentation adequate to meet the desired scientific goals. This paper is primarily concerned with defining possible mission applications, the required electronic systems, and the approaches that are currently being studied for their development.

Jurgens, R. F.↗
NASA NTRS1983

Theory of molecular formation by radiative association in interstellar clouds

A theory of molecular formation by radiative association is presented which is consistent with angular momentum being conserved during the encounter and which incorporates explicitly the long-range attraction between the reactants. It is pointed out that the activated complex would not have a Boltzmann energy distribution should the rotational and kinetic temperatures of the reactants differ, and it is shown how allowance for this may be made. Account is taken of the inaccessibility of a considerable fraction of the nuclear spin states of the complex. Methods are given for treating the effect which the finiteness of the dissociation frequency may have on the association rate. Calculations on some reactions of interest are performed. A very simple semiempirical formula for the rate coefficient for radiative association is also given.

Bates, D. R.↗
NASA NTRS1986

Goldstone solar system radar

Information is provided about physical nature planetary surfaces and their topography as well as dynamical properties such as orbits and spin states using ground based radar as a remote sensing tool. Accessible targets are the terrestrial planets: the Earth's Moon, Mercury, Venus and Mars, the outer planets rings and major moons, and many transient objects such as asteroids and comets. Data acquisition utilizes the unique facilities of the Goldstone Deep Space Network, occasionally the Arecibo radar, and proposed use of the VLA (very large array).

Jurgens, R. F.↗
NASA NTRS1990

Theory of multicolor lattice gas - A cellular automaton Poisson solver

The present class of models for cellular automata involving a quiescent hydrodynamic lattice gas with multiple-valued passive labels termed 'colors', the lattice collisions change individual particle colors while preserving net color. The rigorous proofs of the multicolor lattice gases' essential features are rendered more tractable by an equivalent subparticle representation in which the color is represented by underlying two-state 'spins'. Schemes for the introduction of Dirichlet and Neumann boundary conditions are described, and two illustrative numerical test cases are used to verify the theory. The lattice gas model is equivalent to a Poisson equation solution.

Chen, H.↗
NASA NTRS1990

The spin vector of Venus

Analysis of radar observations from 1964 through 1983 yields the following values for the components of the spin vector of Venus: P = 243.026 + or - 0.006 d (retrograde); alpha = 272.75 + or - 0.09 deg; and delta = 67.10 + or - 0.09 deg, where the standard errors quoted are three- to five-fold larger than the statistical standard errors and encompass the changes in results obtained by various tests designed to expose possible systematic errors. These values demonstrate conclusively that the spin state of Venus is not in resonance with the relative orbital motions of Venus and earth.

Shapiro, I. I.↗