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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 235 records · Page 13
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DOE OSTI2011

m-STATE INTERFERENCE WITH PARTIAL FREQUENCY REDISTRIBUTION FOR POLARIZED LINE FORMATION IN ARBITRARY MAGNETIC FIELDS

The present paper concerns the derivation of polarized partial frequency redistribution (PRD) matrices for scattering on a two-level atom in arbitrary magnetic fields. We generalize the classical theory of PRD that is applicable to a J = 0 {yields} 1 {yields} 0 scattering transition, to other types of atomic transitions with arbitrary quantum numbers. We take into account quantum interference between magnetic substates of a given upper J-state. The generalization proceeds in a phenomenological way, based on the direct analogy between the Kramers-Heisenberg scattering amplitude in quantum mechanics and the Jones scattering matrix in classical physics. The redistribution matrices derived from such a generalization of classical PRD theory are identical to those obtained from a summed perturbative quantum electrodynamic treatment of the atom-radiation interaction. Our semi-classical approach has the advantage that it is non-perturbative, more intuitive, and lends itself more easily to further generalization (like the inclusion of J-state interference in the PRD theory).

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2011

POLARIZED LINE FORMATION WITH J-STATE INTERFERENCE IN THE PRESENCE OF MAGNETIC FIELDS. I. PARTIAL FREQUENCY REDISTRIBUTION IN THE COLLISIONLESS REGIME

Quantum interference phenomena play a fundamental role in astrophysical spectra that are formed by coherent scattering processes. Here we derive a partial frequency redistribution (PRD) matrix that includes J-state interference in the presence of magnetic fields of arbitrary strength. The paper focuses on PRD in the collisionless regime, which in the traditional PRD terminology is referred to as Hummer's type-II scattering. By limiting the treatment to the linear Zeeman regime, for which the Zeeman splitting is much smaller than the fine-structure splitting, it is possible to formulate analytical expressions for the PRD matrices. In the special case of non-magnetic scattering we recover the redistribution matrix derived from an independent quantum electrodynamic formulation based on the metalevel theory.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

The quantum interference effects in the SC II 4247 Å line of the second solar spectrum

The Sc II 4247 Å line formed in the chromosphere is one of the lines well known, like the Na I D{sub 2} and Ba II D{sub 2}, for its prominent triple-peak structure in Q/I and the underlying quantum interference effects governing it. In this paper, we try to study the nature of this triple-peak structure using the theory of F-state interference including the effects of partial frequency redistribution (PRD) and radiative transfer (RT). We compare our results with the observations taken in a quiet region near the solar limb. In spite of accounting for PRD and RT effects, it has not been possible to reproduce the observed triple-peak structure in Q/I. While the two wing PRD peaks (on either side of central peak) and the near wing continuum can be reproduced, the central peak is completely suppressed by the enhanced depolarization resulting from the hyperfine structure splitting. This suppression remains for all the tested widely different one-dimensional model atmospheres or for any multi-component combinations of them. While multidimensional RT effects may improve the fit to the intensity profiles, they do not appear capable of explaining the enigmatic central Q/I peak. This leads us to suspect that some aspect of quantum physics is missing.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2026

Electrostatic gate-controlled quantum interference in a high-mobility two-dimensional electron gas at the (La 0.3 ⁢Sr 0.7 )(Al 0.65 ⁢Ta 0.35 )O 3 /SrTiO 3 interface

Here, we report quantum oscillations in magnetoresistance that are periodic in magnetic field (𝐵), observed at the interface between (La 0.3 ⁢Sr 0.7 )(Al 0.65 ⁢Ta 0.35 )O 3 and SrTiO 3 . Unlike Shubnikov–de Haas oscillations, which appear at magnetic fields > 7 T and diminish quickly as the temperature rises, these 𝐵-periodic oscillations emerge at low fields and persist up to 10 K. Their amplitude decays exponentially with both temperature and field, specifying dephasing of quantum interference. Increasing the carrier density through electrostatic gating results in a systematic reduction in both the amplitude and frequency of the oscillations, with complete suppression beyond a certain gate voltage. We attribute these oscillations to the Altshuler-Aronov-Spivak effect, likely arising from naturally formed closed-loop paths due to the interconnected quasi-one-dimensional conduction channels along SrTiO 3 domain walls. The relatively long phase coherence length (≃ 1.8 µ⁢m at 0.1 K), estimated from the oscillation amplitude, highlights the potential of complex oxide interfaces as a promising platform for exploring quantum interference effects and advancing device concepts in quantum technologies, such as mesoscopic interferometers and quantum sensors.

36 MATERIALS SCIENCE↗
DOE OSTI2011

Interference of parametrically driven one-dimensional ultracold gases

We theoretically analyze interference patterns of parametrically driven one-dimensional ultracold atomic gases. By modulating the interaction strength periodically in time, we propose to excite collective modes in a pair of independent one-dimensional gases at energies corresponding to the drive frequency. The excited collective modes lead to spatial oscillations in the correlations of the interference pattern, which can be analyzed to obtain the sound velocity of the collective modes. We discuss both bosonic and fermionic systems and how such experiments could be used to probe spin-charge separation.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

Quantum interference in a four-level system of a {sup 87}Rb atom: Effects of spontaneously generated coherence

In this work, the effects of quantum interference and spontaneously generated coherence (SGC) are theoretically analyzed in a four-level system of a {sup 87}Rb atom. For the effects of SGC, we find that a new kind of electromagnetically induced transparency channel can be induced due to destructive interference, and the nonlinear Kerr absorption can be coherently narrowed or eliminated under different strengths of the coupling and switching fields.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

Quantum interference in timed Dicke basis and its effect on bipartite entanglement

We analyze the effect of the position-dependent excitation phase on the properties of entanglement between two qubits formed in atomic systems. We show that the excitation phase induces a vacuum-mediated quantum interference in the system that affects the dynamical behavior of entanglement between the qubits. It is also found that the quantum interference leads to a coherent population transfer between the symmetric and antisymmetric states that can considerably modify the dynamics of two-qubit entanglement and can even prevent finite-time disentanglement (sudden death) under certain conditions.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

Interference in above-threshold-ionization electron distributions from molecules

We present quantum-mechanical studies on above-threshold ionization of molecular ions in two and three dimensions. The momentum distributions show signatures of interfering emissions from the molecular centers. These structures deviate from a simple double-slit model that ignores the electron-ion interaction, but they are reproduced by an eikonal model. Such distortions of the interference pattern are partly responsible for the absence of clear interference patterns in the angle-integrated electron energy spectra.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

Nuclear interference in dissociating of HD{sup +} in ultrashort laser fields

The dissociation dynamics of HD{sup +} molecules is studied theoretically by numerically solving the time-dependent Schroedinger equation in which the molecular vibrational and rotational degrees of freedom are included. Based on the Born-Oppenheimer approximation, the ground 1s{sigma}{sub g} state and the excited 2p{sigma}{sub u} state are taken into account, corresponding to two dissociative channels HD{sup +}{yields}D + H{sup +} and HD{sup +}{yields}H + D{sup +}, respectively. Two dissociative nuclear wave packets overlap and interfere after excited by two ultrashort laser pulses. The interference patterns can be controlled by varying the laser parameters and the dissociation probabilities are demonstrated for different laser fields. The kinetic energy-dependent distributions of the fragments are calculated using an asymptotic-flow expression in the momentum space. The branching ratio D{sup +}/(H{sup +} + D{sup +}), as a function of the delay time and the relative phase between two laser pulses, is also discussed.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

Excitation two-center interference and the orbital geometry in laser-induced nonsequential double ionization of diatomic molecules

We address the influence of the molecular orbital geometry and of the molecular alignment with respect to the laser-field polarization on laser-induced nonsequential double ionization of diatomic molecules for different molecular species, namely N{sub 2} and Li{sub 2}. We focus on the recollision excitation with subsequent tunneling ionization (RESI) mechanism, in which the first electron, upon return, promotes the second electron to an excited state, from where it subsequently tunnels. We assume that both electrons are initially in the highest occupied molecular orbital (HOMO) and that the second electron is excited to the lowest unoccupied molecular orbital (LUMO). We show that the electron-momentum distributions exhibit interference maxima and minima due to the electron emission at spatially separated centers. We provide generalized analytical expressions for such maxima or minima, which take into account s-p mixing and the orbital geometry. The patterns caused by the two-center interference are sharpest for vanishing alignment angle and get washed out as this parameter increases. Apart from that, there exist features due to the geometry of the LUMO, which may be observed for a wide range of alignment angles. Such features manifest themselves as the suppression of probability density in specific momentum regions due to the shape of the LUMO wave function, or as an overall decrease in the RESI yield due to the presence of nodal planes.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

Quantum-interference-initiated superradiant and subradiant emission from entangled atoms

We calculate the radiative characteristics of emission from a system of entangled atoms which can have a relative distance larger than the emission wavelength. We develop a quantum multipath interference approach which explains both super- and subradiance though the entangled states have zero dipole moment. We derive a formula for the radiated intensity in terms of different interfering pathways. We further show how the interferences lead to directional emission from atoms prepared in symmetric W states. As a byproduct of our work we show how Dicke's classic result can be understood in terms of interfering pathways. In contrast to the previous works on ensembles of atoms, we focus on finite numbers of atoms prepared in well characterized states.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

Quantum-interference-controlled resonance profiles from lasing without inversion to photodetection

In this work we report a quantum interference mediated control of the resonance profiles in a generic three-level system and investigate its effect on key quantum interference (QI) phenomena. Namely in a three-level configuration with doublets in the ground or excited states, we show control over enhancement and suppression of the emission (absorption) profiles. This is achieved by manipulation of the strength of QI and the energy spacing of the doublets. We analyze the application of such QI-induced control of the resonance profile in the framework of two limiting cases of lasing without inversion and photodetection.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2017

Quantum interference effects on the intensity of the G modes in double-walled carbon nanotubes

The effects of quantum interferences on the excitation dependence of the intensity of G modes have been investigated on single-walled carbon nanotubes [Duque et al., Phys. Rev. Lett.108, 117404 (2012)]. In this work, by combining optical absorption spectroscopy and Raman scattering on individual index identified double-walled carbon nanotubes, we examine the experimental excitation dependence of the intensity of longitudinal optical and transverse optical G modes of the constituent inner and outer single-walled carbon nanotubes. The observed striking dependencies are understood in terms of quantum interference effects. Considering such effects, the excitation dependence of the different components of the G modes permit to unambiguously assign each of them as originating from the longitudinal or transverse G modes of inner and outer tubes.

36 MATERIALS SCIENCE↗
DOE OSTI2011

Interference pattern in the collision of structures in the Bose-Einstein condensate dark matter model: Comparison with fluids

In order to explore nonlinear effects on the distribution of matter during collisions within the Bose-Einstein condensate (BEC) dark matter model driven by the Schroedinger-Poisson system of equations, we study the head-on collision of structures and focus on the interference pattern formation in the density of matter during the collision process. We explore the possibility that the collision of two structures of fluid matter modeled with an ideal gas equation of state also forms interference patterns and found a negative result. Given that a fluid is the most common flavor of dark matter models, we conclude that one fingerprint of the BEC dark matter model is the pattern formation in the density during a collision of structures.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

A general theory of interference fringes in x-ray phase grating imaging

Purpose: The authors note that the concept of the Talbot self-image distance in x-ray phase grating interferometry is indeed not well defined for polychromatic x-rays, because both the grating phase shift and the fractional Talbot distances are all x-ray wavelength-dependent. For x-ray interferometry optimization, there is a need for a quantitative theory that is able to predict if a good intensity modulation is attainable at a given grating-to-detector distance. In this work, the authors set out to meet this need. Methods: In order to apply Fourier analysis directly to the intensity fringe patterns of two-dimensional and one-dimensional phase grating interferometers, the authors start their derivation from a general phase space theory of x-ray phase-contrast imaging. Unlike previous Fourier analyses, the authors evolved the Wigner distribution to obtain closed-form expressions of the Fourier coefficients of the intensity fringes for any grating-to-detector distance, even if it is not a fractional Talbot distance. Results: The developed theory determines the visibility of any diffraction order as a function of the grating-to-detector distance, the phase shift of the grating, and the x-ray spectrum. The authors demonstrate that the visibilities of diffraction orders can serve as the indicators of the underlying interference intensity modulation. Applying the theory to the conventional and inverse geometry configurations of single-grating interferometers, the authors demonstrated that the proposed theory provides a quantitative tool for the grating interferometer optimization with or without the Talbot-distance constraints. Conclusions: In this work, the authors developed a novel theory of the interference intensity fringes in phase grating x-ray interferometry. This theory provides a quantitative tool in design optimization of phase grating x-ray interferometers.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

Enhancing the Resistance of Spectral Characteristics of Interference Coatings to Deviation in Parameters of Layers Entering into Their Composition

A new method of enhancing the resistance of spectral characteristics of interference coatings to deviations in parameters of layers entering into their composition is presented. The spectral characteristic that can be obtained using this method for the energy transmittance (or reflectance) of an experimentally manufactured coating is maximally close to the characteristic of the synthesized coating. A way to use several samples for monitoring the thickness of layers during the process of their formation with the aim to reduce the deviation of optical layers during manufacturing of interference coatings is presented.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Optical magnetic resonances induced by the interference of reactive components in the near radiation-field zone of atoms in a glow discharge of a mixture of even neon isotopes

Four types of anomalous optical magnetic resonances shifted with respect to the zero magnetic field and with different shapes are found in radiation of a glow discharge in a mixture of even neon isotopes placed in a swept longitudinal magnetic field. This testifies to the manifestation of collective processes of synchronous light emission by oscillators belonging to isotopically different spatially separated atoms in discharge plasma. The origin of resonances is associated with nonstationary interference of reactive fields in the near radiation-field zones of emission of atoms, averaged over the lifetime of the fields (interference), while different types of resonances are associated with different methods of synchronization of the phases of the fields.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗