Quadrupole Resonance Research Articles

Complete mode conversion between longitudinal and transverse waves by an elastic metamaterial slab with a double-scatterer structure

In this work, we propose a design of a double-scatterer structure to achieve complete conversion for elastic bulk waves. Every unit of the elastic metamaterial slab contains a pair of scatterers with a relatively oblique direction. When the slab attaches on a semi-infinite solid background, it can completely convert the normal incident longitudinal wave into the reflected shear wave, or vice versa. The conversion can be attributed to the in-phase coupling of the double scatterers’ quadrupolar resonances. The coupled two quadrupoles could interact with the background and bring oblique displacements. Consequently, the oblique displacements generate horizontal displacements for reflected waves.

Reanalysis of the hyperfine structure of Co II. Determination of the nuclear quadrupole moment of 59Co

The paper re-analyses the hyperfine structure using a semi-empirical method made possible by new precise experimental data. By incorporating electric quadrupole interactions into the calculations, we were able to determine the nuclear quadrupole moment of 59Co. We compared the results with existing experimental data and theoretical calculations. Additionally, we provide predicted values for the magnetic dipole A and electric quadrupole B hyperfine structure constants for both even and odd levels.

Nuclear quadrupole resonance spectroscopy with a femtotesla diamond magnetometer.

Radio frequency (RF) magnetometers based on nitrogen vacancy centers in diamond are predicted to offer femtotesla sensitivity, but previous experiments were limited to the picotesla level. We demonstrate a femtotesla RF magnetometer using a diamond membrane inserted between ferrite flux concentrators. The device provides ~300-fold amplitude enhancement for RF magnetic fields from 70 kHz to 3.6 MHz, and the sensitivity reaches ~70 fT√s at 0.35 MHz. The sensor detected the 3.6-MHz nuclear quadrupole resonance (NQR) of room-temperature sodium nitrite powder. The sensor's recovery time after an RF pulse is ~35 μs, limited by the excitation coil's ring-down time. The sodium-nitrite NQR frequency shifts with temperature as -1.00±0.02 kHz/K, the magnetization dephasing time is T2*=887±51 μs, and multipulse sequences extend the signal lifetime to 332±23 ms, all consistent with coil-based studies. Our results expand the sensitivity frontier of diamond magnetometers to the femtotesla range, with potential applications in security, medical imaging, and materials science.

Many-body quantum muon effects and quadrupolar coupling in solids

Strong quantum zero-point motion (ZPM) of light nuclei and other particles is a crucial aspect of many state-of-the-art quantum materials. However, it has only recently begun to be explored from an ab initio perspective, through several competing approximations. Here we develop a unified description of muon and light nucleus ZPM and establish the regimes of anharmonicity and positional quantum entanglement where different approximation schemes apply. Via density functional theory and path-integral molecular dynamics simulations we demonstrate that in solid nitrogen, α–N2, muon ZPM is both strongly anharmonic and many-body in character, with the muon forming an extended electric-dipole polaron around a central, quantum-entangled [N2–μ–N2]+ complex. By combining this quantitative description of quantum muon ZPM with precision muon quadrupolar level-crossing resonance experiments, we independently determine the static 14N nuclear quadrupolar coupling constant of pristine α–N2 to be –5.36(2) MHz, a significant improvement in accuracy over the previously-accepted value of –5.39(5) MHz, and a validation of our unified description of light-particle ZPM.

Suppression of Coulomb-nuclear interference in the near-barrier elastic scattering of 17Ne from 208Pb

The proton drip-line nucleus 17Ne is considered a good candidate for a Borromean two-proton halo with a 15O + p + p structure. Angular distributions of the elastic scattering and inclusive 15O production for a 136 MeV 17Ne beam incident on a 208Pb target were measured for the first time at the SPIRAL1 facility, GANIL. Use of the GLORIA detector array allowed high-resolution data over a wide angular range from 20∘ up to 95∘ in the laboratory frame to be obtained. The elastic scattering angular distribution shows similarities with those for both 6He and 20Ne at equivalent collision energies with respect to the corresponding Coulomb barriers, exhibiting the suppression of the Coulomb rainbow peak characteristic of strong coupling. Optical model and coupled channel fits suggest that this is due to a combination of coupling to low-lying quadrupole resonances and Coulomb dipole coupling to the low-lying continuum, although their relative importance depends on the relevant B(E2) values which remain to be firmly determined.

Narrow resonance line-widths and high figure of merits via composite nanopillar dimer array sensors

The Ag/Si/SiO2 composite nanopillar dimer array sensor is put forward to form a surface lattice resonance (SLR) with strong intensity and narrow resonance line-width. In the Ag/Si/SiO2 composite nanopillar dimer array, Ag nanopillar dimers sit on Si nanopillar dimers, and Si nanopillar dimers sit on SiO2 nanopillar dimers, which sit on a quartz substrate. Simulated results demonstrate that the line-width can be as narrow as 2.1 nm. This is mainly attributed to the coupling between the combination of single Ag nanopillar dimers' local surface plasmon quadrupole (Q) resonance and Si nanopillar dimers' Mie resonance with the array's diffraction waves. However, for the Ag/Si/SiO2 composite nanopillar array (without dimers), the SLR intensity is too weak for the sensing applications. Compared to the Ag/Si/SiO2 composite nanopillar array, the superiority of the Ag/Si/SiO2 composite nanopillar dimer array is that the near-field coupling in the dimer can further improve Ag nanopillar dimers' Q resonance and Si nanopillar dimers' Mie resonance. Therefore, SLR intensity can be significantly enhanced with only a slight increase in line-width, thus the sensing detection range is wider. The array's period, the height and diameter of Ag/Si/SiO2 nanopillars have notable effects on the SLR. Benefiting from the narrow line-width, the figure of merit (FOM) can reach a value of 226. This work is important to improve the optical sensor based on SLRs.

Position and Orientation dependent Hybridization and Energy transfer of Dipole Emitter around Plasmonic Homodimers

AbstractA dipole emitter (analogous to organic molecules) placed near any dielectric or metal nanoparticles, based on their spatially constrained location and orientation, vividly emulate optical nanoantennas. Herein, we have extensively simulated the single dipole emitter interaction with spherical homodimers of noble metal gold and silver nanoparticles for different positional dependent orientations, exemplifying systematically the hybridization (Rabi splitting), quenching and diffuse non‐radiative energy transfer effects. The blue‐shifted scattering spectra of the coupled dipole emitter with individual Ag and Au homodimers quantify and corroborate the corresponding quantum yield/efficiency estimations. Such spatially oriented emitter interaction further distinctly reveals the enhanced near‐field and far‐field effects of the plasmonic dimer system in terms of dipolar and quadrupolar resonances, arising due to the induced polarization by respective incident electric and opto‐magnetic field components. Understanding the surface‐enhanced behavior of organic molecules that are either incorporated or randomly attached (experimentally) on the surface of metal nanoparticles will benefit greatly from the present comprehensive data analysis.

High refractive index dielectric coating on plasmonic nanoantennas for strong visible light absorption in small transition metal nanoparticle reactors.

A more practical model for plasmonic core@shell-satellite antenna-reactor photocatalysts is promoted. In contrast to the mainstream view, total light absorption in the Pt nanoparticle (NP) reactors can be further improved by 70% after coating a 10-nm-thick high refractive index TiO2 shell on the large Ag antenna as a result of more Pt NPs undergoing high absorption enhancement. The enhancement effect is maximized at the electric quadrupole (EQ) resonance. Considering the high refractive index of the TiO2 coating and the embedding of the Pt NPs, the underlying physics is addressed within classical electrodynamics, making a necessary supplement to the conventional plasmonic near-field enhancement mechanism. These findings provide a general strategy for developing novel, to the best of our knowledge, visible light photocatalysts made of transition metals directly.

Calorimetric measurement of nuclear spin-lattice relaxation rate in metals

The quasiparticle density of states in correlated and quantum-critical metals directly probes the effect of electronic correlations on the Fermi surface. Measurements of the nuclear spin-lattice relaxation rate provide one such experimental probe of quasiparticle mass through the electronic density of states. By far the most common way of accessing the spin-lattice relaxation rate is via nuclear magnetic resonance and nuclear quadrupole resonance experiments, which require resonant excitation of nuclear spin transitions. Here we report non-resonant access to spin-lattice relaxation dynamics in AC-calorimetric measurements. The nuclear spin-lattice relaxation rate is inferred in our measurements from its effect on the frequency dispersion of the thermal response of the calorimeter-sample assembly. We use fast, lithographically-defined nanocalorimeters to access the nuclear spin-lattice relaxation times in metallic indium from 0.3~K to 7~K and in magnetic fields up to 35~T.

Commensurate-to-incommensurate transition of charge-density-wave order and a possible quantum critical point in pressurized kagome metal CsV3Sb5

Clarifying the interplay between charge-density waves (CDWs) and superconductivity is important in the kagome metal CsV3Sb5, and pressure (P) can play a crucial role. Here, we present 121/123Sb nuclear quadrupole resonance (NQR) measurements under hydrostatic pressures up to 2.43 GPa in CsV3Sb5 single crystals. We demonstrate that the CDW gradually changes from a commensurate modulation with a star-of-David (SoD) pattern to an incommensurate one with a superimposed SoD and Tri-hexagonal (TrH) pattern stacking along the c-axis. Moreover, the linewidth δν of 121/123Sb-NQR spectra increases with cooling down to TCDW, indicating the appearance of a short-range CDW order due to CDW fluctuations pinned by quenched disorders. The δν shows a Curie–Weiss temperature dependence and tends to diverge at Pc ~ 1.9 GPa, suggesting that a CDW quantum critical point (QCP) exists at Pc where Tc shows the maximum. For P > Pc, spin fluctuations are enhanced when the CDW is suppressed. Our results suggest that the maximal Tc at Pc ~ 1.9 GPa is related to the CDW QCP, and the presence of spin fluctuations prevents the Tc from a rapid decrease otherwise, after the CDW is completely suppressed.

Structure of the kagome superconductor CsV3Sb5 in the charge density wave state

The structure of charge density wave states in AV$_3$Sb$_5$ (A = K, Rb, Cs) kagome superconductors remains elusive, with three possible $2a\times2a\times2c$ candidates: tri-hexagonal, star-of-David, and their mixture. In this study, we conducted a systematic first-principles investigation of the nuclear quadrupole resonance (NQR) and nuclear magnetic resonance (NMR) spectra for the $2a\times2a\times2c$ CsV$_3$Sb$_5$ structures. By comparing our simulations with experimental data, we have concluded that the NQR spectrum indicates the tri-hexagonal structure as the proper structure for CsV$_3$Sb$_5$ after its charge density wave phase transition. The NMR calculation results obtained from the tri-hexagonal structure are also consistent with the experimental data.

3D to 0D cesium lead bromide: A 79/81Br NMR, NQR and theoretical investigation

Inorganic metal halides offer unprecedented tunability through elemental variation of simple three-element compositions, but can exhibit complicated phase behaviour, degradation, and microscopic phenomena (disorder/dynamics) that play an integral role for the bulk-level chemical and physical properties of these materials. Understanding the halogen chemical environment in such materials is crucial to addressing many of the concerns regarding implementing these materials in commercial applications. In this study, a combined solid-state nuclear magnetic resonance, nuclear quadrupole resonance and quantum chemical computation approach is used to interrogate the Br chemical environment in a series of related inorganic lead bromide materials: CsPbBr3, CsPb2Br5, and Cs4PbBr6. The quadrupole coupling constants (CQ) were determined to range from 61 to 114 MHz for 81Br, with CsPbBr3 exhibiting the largest measured CQ and Cs4PbBr6 the smallest. GIPAW DFT was shown to be an excellent pre-screening tool for estimating the EFG of Br materials and can increase experimental efficiency by providing good starting estimates for acquisition. Finally, the combination of theory and experiment to inform the best methods for expanding further to the other quadrupolar halogens is discussed.

Elucidating the Role of Noncovalent Interactions in Favipiravir, a Drug Active against Various Human RNA Viruses; a 1H-14N NQDR/Periodic DFT/QTAIM/RDS/3D Hirshfeld Surfaces Combined Study.

Favipiravir (6-fluoro-3-hydroxypyrazine-2-carboxamide, FPV), an active pharmaceutical component of the drug discovered and registered in March 2014 in Japan under the name Avigan, with an indication for pandemic influenza, has been studied. The study of this compound was prompted by the idea that effective processes of recognition and binding of FPV to the nucleic acid are affected predominantly by the propensity to form intra- and intermolecular interactions. Three nuclear quadrupole resonance experimental techniques, namely 1H-14N cross-relaxation, multiple frequency sweeps, and two-frequency irradiation, followed by solid-state computational modelling (density functional theory supplemented by the quantum theory of atoms in molecules, 3D Hirshfeld Surfaces, and reduced density gradient) approaches were applied. The complete NQR spectrum consisting of nine lines indicating the presence of three chemically inequivalent nitrogen sites in the FPV molecule was detected, and the assignment of lines to particular sites was performed. The description of the nearest vicinity of all three nitrogen atoms was used to characterize the nature of the intermolecular interactions from the perspective of the local single atoms and to draw some conclusions on the nature of the interactions required for effective recognition and binding. The propensity to form the electrostatic N-H···O, N-H···N, and C-H···O intermolecular hydrogen bonds competitive with two intramolecular hydrogen bonds, strong O-H···O and very weak N-H···N, closing the 5-member ring and stiffening the structure, as well as π···π and F···F dispersive interactions, were analysed in detail. The hypothesis regarding the similarity of the interaction pattern in the solid and the RNA template was verified. It was discovered that the -NH2 group in the crystal participates in intermolecular hydrogen bonds N-H···N and N-H···O, in the precatalytic state only in N-H···O, while in the active state in N-H···N and N-H···O hydrogen bonds, which is of importance to link FVP to the RNA template. Our study elucidates the binding modes of FVP (in crystal, precatalytic, and active forms) in detail and should guide the design of more potent analogues targeting SARS-CoV-2. Strong direct binding of FVP-RTP to both the active site and cofactor discovered by us suggests a possible alternative, allosteric mechanism of FVP action, which may explain the scattering of the results of clinical trials or the synergistic effect observed in combined treatment against SARS-CoV-2.

Non-invasive authentication of mail packages using nuclear quadrupole resonance spectroscopy

The international postal network is one of the most widely used methods for correspondence throughout the world. Most postal traffic across the globe consists of legitimate interpersonal, business-consumer, and business-business communications. However, the global postal system is also utilized for criminal activity. In particular, it is often utilized to ship and distribute contraband, including illegal psychoactive drugs such as fentanyl and heroin, to consumers. Existing technological solutions are capable of identifying synthetic opioids and other illegal drugs within packages, but are accompanied by several disadvantages that make them unsuitable for large-scale authentication of international mail traffic. This paper presents a novel method for non-invasive authentication of mail packages that overcomes these challenges. The approach uses nuclear quadrupole resonance (NQR) spectroscopy to detect and quantify the presence of known active pharmaceutical ingredients (APIs) within the package. It has been experimentally demonstrated using a bench top prototype. Test results from a variety of package types demonstrate the effectiveness of the proposed authentication approach.

A novel adaptive noise canceling system for urea NQR spectrum analysis

Due to its practical ease of use and sufficiently high reliability, Nuclear Quadrupole Resonance (NQR) has largely been used in remote sensing-based detection of quadrupole nuclei, especially Nitrogen-containing materials. Since the received signal of free induction decay (FID) is inherently weak in this technique, the noise and the interference of the environment would dramatically impair the performance of the detecting systems. To handle such challenges, an adaptive noise canceling method was employed to improve the signal to noise and interference ratio (SNIR) in FID signals. FID signals, noise, and interference were received by the main antenna, while similar noise and interference would be received by the auxiliary antenna. The proposed system significantly reduced noise and interference through the digital noise and interference cancellation algorithm, pulse integration, averaging, and singular spectrum analysis (SSA). Urea powder was empirically analyzed outdoors, suggesting that the proposed adaptive noise and interference cancellation (ANIC) system, effectively suppressed noise and interference by 41.13 dB and amplified the FID signal by 53.36 dB. The strongest signal was detected at 2870.4 kHz.

Transition metal (X = Mn, Fe, Co, Ni, Cu, Zn)-doped graphene as gas sensor for CO2 and NO2 detection: a molecular modeling framework by DFT perspective.

In this research, CO2 and NO2 adsorption on doped nanographene (NG) sheets with transition metals (Fe, Ni, Zn) and (Mn, Co, Cu), respectively, have been applied for scavenging of these toxic gases as the environmental pollutants. The values of changes of atomic charge density have illustrated a more significant charge transfer for Ni-doped C-NG through CO2 adsorption and a more remarkable charge transfer for Co-doped C-NG through NO2 adsorption. The data of NMR spectroscopy has depicted several fluctuations around the graph of Zn-doped on the nanographene surface. The thermodynamic results from IR spectroscopy have indicated that [Formula: see text] values are almost similar for doped metal transitions of Mn, Co, and Cu on the C-NG nanosheet, while [Formula: see text] has the largest gap of Gibbs free energy adsorption with dipole moment. The Langmuir adsorption model with a three-layered ONIOM using CAM-B3LYP functional accompanying LANL2DZ, EPR-III and 6-31 + G (d,p) basis sets due to Gaussian 16 revision C.01 program on the complexes of CO2 → (Fe, Ni, Zn) and NO2 → (Mn, Co, Cu) doped on the C-NG has been accomplished. Then, NMR and IR spectroscopy, nuclear quadrupole resonance, and natural bond orbital analysis have been accomplished for evaluating chemical shielding tensors, thermodynamic properties, electric potential, and occupancy fluctuation through bond orbitals, respectively. In addition, frontier orbitals of LUMO, HOMO, and also a series of chemical reactivity parameters have been calculated. Finally, time-dependent-DFT method due to UV-VIS spectrums has been accomplished to discern the low-lying excited states of CO2 and NO2 adsorption on the (Fe, Ni, Zn) and (Mn, Co, Cu), respectively, doped C-NG sheet.

Consistent optical potential for incident and emitted low-energy α particles. III. Nonstatistical processes induced by neutrons on Zr, Nb, and Mo nuclei

The reliability of a previous $\alpha$-particle optical-model potential (OMP) on nuclei with mass number 45$\leq$$A$$\leq$209 was proved for emitted $\alpha$ particles as well, for proton--induced reactions on Zn isotopes [Phys. Rev. C {\bf 91}, 064611 (2015), Paper I]. However, the same was not the case of neutrons on Zr stable isotopes [Phys. Rev. C {\bf 96}, 044610 (2017), Paper II]. A recent assessment of this potential also for nucleon--induced $\alpha$-emission on $A$$\sim$60 nuclei, including pickup direct reaction and eventual Giant Quadrupole Resonance (GQR) $\alpha$-emission, is completed for neutrons incident on Zr, Nb, and Mo stable isotopes. Consistent sets of input parameters, determined through analysis of independent data, is involved while no further empirical rescaling factors of the $\gamma$ and nucleon widths have been involved. A suitable account of all competitive reaction channels is confirmed by careful uncertainty analysis, to avoid parameter ambiguities and/or error compensation. Additional validation of this potential is also supported by recently measured $(\alpha,\gamma)$ and $(\alpha,n)$ cross--sections of Zr and Mo nuclei. An increase of the $\alpha$-emission beyond the statistical predictions, through consideration of additional reaction channels of the pickup direct interaction and {\it like}--GQR decay, makes possible the description of both absorption and emission of $\alpha$ particles by the same optical potential.

Observation of multigap and coherence peak in the noncentrosymmetric superconductor CaPtAs: As75 nuclear quadrupole resonance measurements

We present synthesis and $^{75}$As-nuclear quadrupole resonance (NQR) measurements for the noncentrosymmetric superconductor CaPtAs with a superconducting transition temperature $T_c$ of $\sim 1.5$ K. We discovered two different forms of CaPtAs during synthesis; one is a high-temperature tetragonal form that was previously reported, and the other is a low-temperature form consistent with the orthorhombic structure of CaPtP. According to the $^{75}$As-NQR measurement for superconducting tetragonal CaPtAs, the nuclear spin-lattice relaxation rate $1/T_1$ has an obvious coherence peak below $T_c$ and does not follow a simple exponential variation at low temperatures. These findings indicate that CaPtAs is a multigap superconductor and a large $s$-wave component.

Symmetry Analysis of Zero-Field Antiferroquadrupole Order in CeB6: Extremely Low-Frequency 11B-NQR Study

The zero-field state in the antiferroquadrupole (AFQ) ordered phase of CeB6 has been investigated by a 11B-nuclear quadrupole resonance (NQR) measurement that is sensitive to changes in local charge distribution. In order to achieve this experiment, we have improved our low-frequency NQR techniques, so that the 11B-NQR spectrum has been successfully observed at an NQR frequency νQ ∼ 560 kHz, exceptionally low frequency among direct NQR measurements on strongly correlated electron systems. The temperature dependence of the NQR spectrum reveals that νQ rapidly decreases just below AFQ ordering temperature TQ = 3.3 K, while the spectral shape does not show any sign of site splitting below TQ. The latter is incompatible with the theoretical prediction based on the Oxy-type AFQ order, suggesting that the ordered state in the zero-field region differs from that in the nonzero-field region. Some new possible interpretations to explain the obtained results are proposed.

The impact of the SnI2 purity on the formation of CsSnI3 perovskite modifications as monitored by 127I Nuclear Quadrupole Resonance

The relative content of the perovskite phase in two CsSnI3 samples (of 99.900 and 99.999 wt% SnI2 and 99.999 wt% CsI purity) was estimated using 127I NQR. The results showed that both samples contained the non-perovskite orthorhombic phase as an admixture. In the sample of higher purity (99.999 wt%) its content was insignificant – only trace amounts could be observed at 77 K, whereas at room temperature the presence of the non-perovskite phase was not revealed. However, in the sample of 99.900 wt% purity the content of the non-perovskite phase has reached at least a third of the sample amount, which is due to the probable crystallization of the non-perovskite phase on impurities.