Fine Structure Interactions Research Articles

Kelvin–Helmholtz Instability “Tube” and “Knot” Dynamics. Part III: Extension of Elevated Turbulence and Energy Dissipation into Increasingly Viscous Flows

Abstract A companion paper by Fritts et al. reviews extensive evidence for Kelvin–Helmholtz instability (KHI) “tube” and “knot” (T&K) dynamics at multiple altitudes in the atmosphere and in the oceans that reveal these dynamics to be widespread. A second companion paper by Fritts and Wang reveals KHI T&K events at larger and smaller scales to arise on multiple highly stratified sheets in a direct numerical simulation (DNS) of idealized, multiscale gravity wave–fine structure interactions. These studies reveal the diverse environments in which KHI T&K dynamics arise and suggest their potentially ubiquitous occurrence throughout the atmosphere and oceans. This paper describes a DNS of multiple KHI evolutions in wide and narrow domains enabling and excluding T&K dynamics. These DNSs employ common initial conditions but are performed for decreasing Reynolds numbers (Re) to explore whether T&K dynamics enable enhanced KHI-induced turbulence where it would be weaker or not otherwise occur. The major results are that KHI T&K dynamics extend elevated turbulence intensities and energy dissipation rates ε to smaller Re. We expect these results to have important implications for improving parameterizations of KHI-induced turbulence in the atmosphere and oceans. Significance Statement Turbulence due to small-scale shear flows plays important roles in the structure and variability of the atmosphere and oceans extending to large spatial and temporal scales. New modeling reveals that enhanced turbulence accompanies Kelvin–Helmholtz instabilities (KHIs) that arise on unstable shear layers and exhibit what were initially described as “tubes” and “knots” (T&K) when they were first observed in early laboratory experiments. We perform new modeling to explore two further aspects of these dynamics: 1) can KHI T&K dynamics increase turbulence intensities compared to KHI without T&K dynamics for the same initial fields and 2) can KHI T&K dynamics enable elevated turbulence and energy dissipation extending to more viscous flows? We show here that the answer to both questions is yes.

Natural non-Hermitian interaction alignment with photon-phonon quantization in Eu3+: NaYF4

We investigated the photon and phonon alignment for two dressing interaction profile in Eu+3: NaYF4. The evolution from strong to weak interaction alignment can be controlled by time gate width and time gate position, which shows that time gate position seems more sensitive than time gate width, while changing both can make interaction alignment oscillation due to two phonon and one photon quantization. Fluorescence FL signal switch from dip to peak interaction profile due to strong gamma, while the Super-Fluorescence SFWM signal switch from peak to dip interaction profile due to strong Rabi frequency (G). Comparing single laser spectral alignment to two-laser interaction alignment, the FL and SFWM shows dressing peak dip switch (spectral to interaction profile). In contrast, there is no switch in AT (spectral to interaction profile) because, the phase difference of the second laser balances the destructive and constructive dressing quantization’s. Such results can have potential applications in fine and hyper structure interaction alignment in non-polar ion.

Coherence control in helium-ion ensembles

The authors show how an attosecond XUV-pump IR-probe sequence can be used to ionize the helium atom and create a polarized ion whose coherence is controllable through the pump-probe delay and can be reconstructed from the picosecond fluctuations of the ionic dipole caused by fine-structure interactions.

Features of High-Frequency EPR/ESE/ODMR Spectroscopy of NV-Defects in Diamond

The methods of high-frequency electron paramagnetic resonance (EPR), electron spin echo (ESE) and optically detected magnetic resonance (ODMR) are used to study the unique properties of nitrogen-vacancy (NV) defects in diamond in strong magnetic fields. It is shown that in strong magnetic fields (∼3–5 T) there occurs an effective optically induced alignment of populations of spin levels resulting in filling the level MS = 0 and emptying of the levels MS = ±1, that makes it possible to record ODMR using the change in the intensity of photoluminescence which reaches 10% at resonance. It is demonstrated that the efficiency of the alignment has the same order as in zero and low magnetic fields. The samples were preliminary studied by the ODMR method in zero magnetic fields that allowed accurate determination of the main parameters of the fine structure and hyperfine interactions with nitrogen nuclei, as well as dipole-dipole interactions between the NV center and deep nitrogen donors in the form of a nitrogen atom replacing carbon, N0. Hyperfine interactions with the nearest carbon atoms (isotope 13C) were observed in the high-frequency ODMR spectra, that opens up opportunities for measuring the processes of dynamic polarization of carbon nuclei in strong magnetic fields using optical methods. It is assumed that narrow ODMR lines in strong magnetic fields can be used to measure these fields with submicron spatial resolution. A new method for recording ODMR of NV centers with microwave frequency modulation has been developed, which simplifies the technique of measuring high magnetic fields. A significant increase in the intensity of the ODMR signal was demonstrated when a strong magnetic field was oriented along the symmetry axis of the NV center.

Особенности высокочастотной ЭПР/ЭСЭ/ОДМР спектроскопии NV-дефектов в алмазе

Methods of high-frequency electron paramagnetic resonance (EPR), electron spin echo (ESE), and optically detectable magnetic resonance (ODMR) were used to study the unique properties of nitrogen-vacancy defects (nitrogen-vacancy NV center) in diamond in strong magnetic fields. It has been shown that in strong magnetic fields (3 to 5 T), an effective optically-induced alignment of populations of spin levels occurs, with filling of the MS=0 level and emptying of the MS=1 levels, which allowed to observe ODMR via variations of the photoluminescence intensity, reaching 10% at resonance. It has been demonstrated that this efficiency in high magnetic fields is of the same order as that in zero and low magnetic fields. The samples were preliminarily studied by ODMR in zero magnetic fields, which made it possible to accurately determine the main parameters of the fine structure and hyperfine interactions with nitrogen nuclei, as well as dipole-dipole interactions between the NV center and deep nitrogen donors (nitrogen atom replacing carbon, N0). In the spectra of high-frequency ODMR, hyperfine interactions with the nearest carbon atoms (13C isotope) were observed, which opens up possibilities for optical measurements of the processes of dynamic nuclear polarization of carbon in strong magnetic fields. Narrow ODMR lines in high magnetic fields are supposed to be used to measure these fields with submicron spatial resolution. A new method for detecting ODMR of NV centers with modulation of the microwave frequency has been developed, which simplifies the technique of measuring high magnetic fields. A significant increase in the intensity of the ODMR signal at orientation of the magnetic field along the symmetry axis of NV center was demonstrated.

Non-Abelian geometric potentials and spin-orbit coupling for periodically driven systems

We demonstrate the emergence of the non-Abelian geometric potentials and thus the three-dimensional (3D) spin-orbit coupling (SOC) for ultracold atoms without using the laser beams. This is achieved by subjecting an atom to a periodic perturbation which is the product of a position-dependent Hermitian operator $\hat{V}\left(\mathbf{r}\right)$ and a fast oscillating periodic function $f\left(\omega t\right)$ with a zero average. To have a significant spin-orbit coupling (SOC), we analyze a situation where the characteristic energy of the periodic driving is not necessarily small compared to the driving energy $\hbar\omega$. Applying a unitary transformation to eliminate the original periodic perturbation, we arrive at a non-Abelian (non-commuting) vector potential term describing the 3D SOC. The general formalism is illustrated by analyzing the motion of an atom in a spatially inhomogeneous magnetic field oscillating in time. A cylindrically symmetric magnetic field provides the SOC involving the coupling between the spin $\mathbf{F}$ and all three components of the orbital angular momentum (OAM) $\mathbf{L}$. In particular, the spherically symmetric monopole-type synthetic magnetic field $\mathbf{B}\propto\mathbf{r}$ generates the 3D SOC of the $\mathbf{L}\cdot \mathbf{F}$ form, which resembles the fine-structure interaction of hydrodgen atom. However, the strength of the SOC here goes as $1/r^{2}$ for larger distances, instead of $1/r^3$ as in atomic fine structure. Such a longer-ranged SOC significantly affects not only the lower states of the trapped atom, but also the higher ones. Furthermore, by properly tailoring the external trapping potential, the ground state of the system can occur at finite OAM, while the ground state of hydrogen atom has zero OAM.

Updated Zeeman effect splitting coefficients for molecular oxygen in planetary applications

We comment on a common practice to use pure Hund case (b) Zeeman parameters in planetary atmospheric radiative transfer applications involving molecular oxygen. A detailed theoretical formulation is presented for the Zeeman splitting coefficients of molecular oxygen in its ground vibronic state, taking also the relevant fine-structure interactions into account. The updated Zeeman parameters are compared to the simplified Hund case (b) approach used in earlier works. The biggest differences between the output of these formulations occur for states with low rotational energy, and the differences are greater for 16O18O than for 16O2. To get the order of magnitude error introduced by the simplification of the splitting coefficient computations, we perform a limited case study of forward simulations for a few space-borne and ground-based instruments. Our analysis shows that using simplified Zeeman coefficients introduces errors in the forward modelled radiation varying from insignificant up to 10 K.

Virtual Resonant Emission and Oscillatory Long-Range Tails in van der Waals Interactions of Excited States: QED Treatment and Applications.

We report on a quantum electrodynamic (QED) investigation of the interaction between a ground state atom with another atom in an excited state. General expressions, applicable to any atom, are indicated for the long-range tails that are due to virtual resonant emission and absorption into and from vacuum modes whose frequency equals the transition frequency to available lower-lying atomic states. For identical atoms, one of which is in an excited state, we also discuss the mixing term that depends on the symmetry of the two-atom wave function (these evolve into either the gerade or the ungerade state for close approach), and we include all nonresonant states in our rigorous QED treatment. In order to illustrate the findings, we analyze the fine-structure resolved van der Waals interaction for nD-1S hydrogen interactions with n=8, 10, 12 and find surprisingly large numerical coefficients.

Coordination of the Mn4+-Center in Layered Li[Co0.98Mn0.02]O2 Cathode Materials for Lithium-Ion Batteries

Abstract The local coordination of the manganese in Li[Co0.98Mn0.02]O2 cathode materials for lithium-ion batteries has been investigated by means of a joint XRD and multi-frequency electron paramagnetic resonance (EPR) characterization approach. EPR showed the manganese being in a tetravalent high-spin Mn4+-oxidation state with S = 3 2 . $S = {3 \over 2}.$ The set of spin-Hamiltonian parameters obtained from the multi-frequency EPR analysis with Larmor frequencies ranging between 9.4 and 406 GHz is transformed into structural information by means of the recently introduced Monte-Carlo Newman-superposition modeling. Based on this analysis, the Mn4+ are shown being incorporated for the Co3+-sites, i.e. acting as donor-type functional centers Mn Co • ${\rm{Mn}}_{{\rm{Co}}}^ \bullet $ . In that respect, for Mn4+ the negative sign of the axial second-order fine-structure interaction parameter B 2 0 $B_2^0$ is indicative of an elongated oxygen octahedron in its first coordination sphere, whereas B 2 0 > 0 $B_2^0 > 0$ rather points to a compressed octahedron coordinated about the Mn4+-centers. Furthermore, the results obtained here suggest that the oxygen octahedron about the Mn4+-ion is slightly distorted as compared to the CoO6 octahedron. Concerning the coordination to next-nearest neighbor ions, part of the manganese resides in manganese-rich domains, whereas the for the remaining centers the Co3+-site is randomly occupied with Co/Mn according to the effective stoichiometry of the compound. Finally, a structural stability range emerges from the Newman-modeling that supports the discussed ability of manganese to act as an structure-stabilizing element in layered oxides.

Hyperfine structure of the hydroxyl free radical (OH) in electric and magnetic fields

We investigate single-particle energy spectra of the hydroxyl free radical (OH) in the lowest electronic and rovibrational level under combined static electric and magnetic fields, as an example of heteronuclear polar diatomic molecules. In addition to the fine-structure interactions, the hyperfine interactions and centrifugal distortion effects are taken into account to yield the zero-field spectrum of the lowest manifold to an accuracy of less than 2 kHz. We also examine level crossings and repulsions in the hyperfine structure induced by applied electric and magnetic fields. Compared to previous work, we found more than 10% reduction of the magnetic fields at level repulsions in the Zeeman spectrum subjected to a perpendicular electric field. In addition, we find new level repulsions, which we call Stark-induced hyperfine level repulsions, that require both an electric field and hyperfine structure. It is important to take into account hyperfine structure when we investigate physics of OH molecules at micro-Kelvin temperatures and below.

A Continuous-Wave Electron Paramagnetic Resonance Study of Carbon Dioxide Adsorption on the Metal–Organic Frame-Work MIL-53

Continuous-wave electron paramagnetic resonance spectroscopy is applied to explore the adsorption of carbon dioxide (CO2) over the metal organic framework (MOF) MIL-53. Therefore, paramagnetic Cr3+ ions, which replace a small amount of the bulk Al3+ ions in MIL-53(Al/Cr), are used as magnetically active probes. CO2 was adsorbed on samples of MIL-53(Al/Cr) at equilibrium pressures between 0 and 2.5 bar. The transformation from the large pore phase to the narrow pore phase of MIL-53 was observed by electron paramagnetic resonance spectroscopy at small CO2 pressures between 0.2 and 0.4 bar, which is in accordance with adsorption results reported in literature. By analyzing the electron paramagnetic resonance signal intensities of the corresponding Cr3+ probes, the ratio between the amount of the narrow pore phase and the large pore phase before and after this phase transformation was quantified. A small fraction of the large pore phase remains even after this phase transition. CO2 adsorption at 77 K indicates the occurrence of the transformation of this MOF from a narrow pore phase to a large pore phase triggered by the adsorbed CO2. Similar observations were already made using powder X-ray diffraction or infrared spectroscopy. But in contrast to these methods electron paramagnetic resonance spectroscopy on Cr3+ seems to be very sensitive not only to large differences between crystallographic conformations like large pores and narrow pores but also to different amounts and configurations of CO2 molecules trapped in the same structural phase of MIL-53, taking advantage of the high sensitivity of the fine structure interaction of Cr3+.

Gravity Wave–Fine Structure Interactions. Part II: Energy Dissipation Evolutions, Statistics, and Implications

Abstract Part I of this paper employs four direct numerical simulations (DNSs) to examine the dynamics and energetics of idealized gravity wave–fine structure (GW–FS) interactions. That study and this companion paper were motivated by the ubiquity of multiscale GW–FS superpositions throughout the atmosphere. These DNSs exhibit combinations of wave–wave interactions and local instabilities that depart significantly from those accompanying idealized GWs or mean flows alone, surprising dependence of the flow evolution on the details of the FS, and an interesting additional pathway to instability and turbulence due to GW–FS superpositions. This paper examines the mechanical and thermal energy dissipation rates occurring in two of these DNSs. Findings include 1) dissipation that tends to be much more localized and variable than that due to GW instability in the absence of FS, 2) dissipation statistics indicative of multiple turbulence sources, 3) strong influences of FS shears on instability occurrence and turbulence intensities and statistics, and 4) significant differences between mechanical and thermal dissipation rate fields having potentially important implications for measurements of these flows.

Gravity Wave–Fine Structure Interactions. Part I: Influences of Fine Structure Form and Orientation on Flow Evolution and Instability

Abstract Four idealized direct numerical simulations are performed to examine the dynamics arising from the superposition of a monochromatic gravity wave (GW) and sinusoidal linear and rotary fine structure in the velocity field. These simulations are motivated by the ubiquity of such multiscale superpositions throughout the atmosphere. Three simulations explore the effects of linear fine structure alignment along, orthogonal to, and at 45° to the plane of GW propagation. These reveal that fine structure alignment with the GW enables strong wave–wave interactions, strong deformations of the initial flow components, and rapid transitions to local instabilities and turbulence. Increasing departures of fine structure alignment from the GW yield increasingly less efficient wave–wave interactions and weaker or absent local instabilities. The simulation having rotary fine structure velocities yields wave–wave interactions that agree closely with the aligned linear fine structure case. Differences in the aligned GW fields are only seen following the onset of local instabilities, which are delayed by about 1–2 buoyancy periods for rotary fine structure compared to aligned, linear fine structure. In all cases, local instabilities and turbulence primarily accompany strong superposed shears or fluid “intrusions” within the rising, and least statically stable, phase of the GW. For rotary fine structure, local instabilities having preferred streamwise or spanwise orientations often arise independently, depending on the character of the larger-scale flow. Wave–wave interactions play the greatest role in reducing the initial GW amplitude whereas fine structure shears and intrusions are the major source of instability and turbulence energies.

Excitation cross-sections by electron impact for O V and O VI levels

Radiative atomic and electron impact excitation data for O V and O VI ions have been calculated. The radiative atomic data have been calculated with the AUTOSTRUCTURE code. Besides the onebody and the two-body fine structure interactions, the two-body non-fine structure operators of the Breit–Pauli Hamiltonian, namely contact spin–spin, two-body Darwin and orbit–orbit are incorporated in AUTOSTRUCTURE. The scattering problem has been treated in the Breit–Pauli distorted wave approximation using the same code AUTOSTRUCTURE .T he OV atomic calculations have been extended from 46 to 92 levels. We have calculated excitation cross-sections for the O V 2s 2 −2s2p and the O VI 2s−2p transitions at energies near the corresponding excitation threshold regions. We have also calculated collision strengths for transitions from the most important levels for collisional excitation at electron energies up to 120 Ry for O V and up to 140 Ry for O VI. Our results have been compared with the available theoretical/experimental ones and a satisfactory agreement has been found between them.

Fine structure of open-shell diatomic molecules in combined electric and magnetic fields

We present a theoretical study of the impact of an electric field combined with a magnetic field on the rotational dynamics of open-shell diatomic molecules. Within the rigid rotor approximation, we solve the time-independent Schrödinger equation including the fine-structure interactions and the Λ-doubling effects. We consider three sets of molecule-specific parameters and several field regimes and investigate the interplay between the different interactions identifying the dominant one. The possibility of inducing couplings between the spin and rotational degrees of freedom is demonstrated.

Sensitive imaging of electromagnetic fields with paramagnetic polar molecules

We propose a method for sensitive parallel detection of low-frequency electromagnetic fields based on the fine structure interactions in paramagnetic polar molecules. Compared to the recently implemented scheme employing ultracold $^{87}$Rb atoms [B{\"o}hi \textit{et al.}, Appl. Phys. Lett. \textbf{97}, 051101 (2010)], the technique based on molecules offers a 100-fold higher sensitivity, the possibility to measure both the electric and magnetic field components, and a probe of a wide range of frequencies from the dc limit to the THz regime.

Estimation of many-body quantum Hamiltonians via compressive sensing

We develop an efficient and robust approach to Hamiltonian identification for multipartite quantum systems based on the method of compressed sensing. This work demonstrates that with only O(s log(d)) experimental configurations, consisting of random local preparations and measurements, one can estimate the Hamiltonian of a d-dimensional system, provided that the Hamiltonian is nearly s-sparse in a known basis. We numerically simulate the performance of this algorithm for three- and four-body interactions in spin-coupled quantum dots and atoms in optical lattices. Furthermore, we apply the algorithm to characterize Hamiltonian fine structure and unknown system-bath interactions.

Local coordination of Fe3+ in Li[Co0.98Fe0.02]O2 as cathode material for lithium ion batteries—multi-frequency EPR and Monte-Carlo Newman-superposition model analysis

The local coordination of the Fe(3+)-centers in Li[Co(0.98)Fe(0.02)]O(2) cathode materials for lithium-ion batteries has been investigated by means of XRD and multi-frequency EPR spectroscopy. EPR clearly showed the Fe(3+) being in a high-spin state with S = 5/2. The set of spin-Hamiltonian parameters obtained from multi-frequency EPR experiments with Larmor frequencies ranging between 9.8 and 406 GHz was transformed into structural information by means of an expansion to standard Newton-superposition modeling, termed as Monte-Carlo Newman superposition modeling. Based on this analysis, an isovalent incorporation of the Fe(3+)-ions on the Co(3+)-sites, i.e. Fe(x)(Co), has been shown. With that respect, the positive sign of the axial second-order fine-structure interaction parameter B(0)(2) is indicative of an elongated oxygen octahedron, whereas B(0)(2) < 0 points to a compressed octahedron coordinated about the Fe(3+)-center. Furthermore, the results obtained here suggest that the oxygen octahedron about the Fe(3+)-ion is slightly distorted as compared to the CoO(6) octahedron, which in turn may impose mechanical strain to the cathode material.

Gravity wave–fine structure interactions: A reservoir of small‐scale and large‐scale turbulence energy

A direct numerical simulation of gravity wave – fine structure interactions is performed to evaluate the effects of such a superposition on instability and turbulence for fine structure shears and a gravity wave (GW) amplitude that are individually stable. The superposition leads to deformations of the fine structure and GW fields that exhibit Kelvin‐Helmholtz (KH) shear instabilities and turbulence extending over more than 20 buoyancy periods. KH instabilities occur on multiple scales, deplete the kinetic energy of the initial fine structure, and yield a layering of the potential temperature field resembling “sheet and layer” structures observed in the oceans and the atmosphere. The interactions have a much smaller effect on the GW amplitude. Such interactions among GWs and fine structure are likely ubiquitous throughout the atmosphere and oceans and may account for sporadic bursts of turbulence and its persistence in regions of apparent static and dynamic stability (Ri &gt; 1/4).

Hyperfine Suppression of2 S13−3 PJ3Transitions inHe3

Two anomalously weak transitions within the 2(3)S_(1)--3(3)P_(J) manifolds in 3He have been identified. Their transition strengths are measured to be 1000 times weaker than that of the strongest transition in the same group. This dramatic suppression of transition strengths is due to the dominance of the hyperfine interaction over the fine-structure interaction. An alternative selection rule based on IS coupling (where the nuclear spin is first coupled to the total electron spin) is proposed. This provides qualitative understanding of the transition strengths. It is shown that the small deviations from the IS coupling model are fully accounted for by an exact diagonalization of the strongly interacting states.