Electric Quadrupole Interaction Research Articles

Second-harmonic generation of 2D materials excited by the Laguerre-Gaussian beam.

We theoretically study the second-harmonic generation (SHG) of two-dimensional (2D) materials excited by a Laguerre-Gaussian (LG) beam at normal incidence and provide a method to distinguish SHG induced by the electric dipole (ED) interaction and SHG induced by the electric quadrupole and magnetic dipole (EQ-MD) interaction by their different dependence on the LG beam parameters, including the effective spot area v02 and the order of orbital angular momentum (OAM) m. In an approximation of neglecting reflection and taking a beam radius to infinity, the intensity of the ED induced SHG is proportional to F m/v02 with Fm = 2-2|m|(2|m|)!/(π(|m|!)2), while the EQ-MD induced one is proportional to (4|m|+2)F m/v04. An in-plane isotropic substrate can strongly affect the signal amplitude but slightly change the v0 and m dependence. Our results provide an all-optical way to detect the OAM by SHG, as well as a theoretical basis for studying the EQ-MD induced SHG by the LG beams.

Plasmon-enhanced chiral absorption through electric dipole–electric quadrupole interaction

Enantioselective interactions of chiral molecules include distinct absorptions to opposite-handed circularly polarized light, known as chiral absorption. Traditionally, chiral absorption has been primarily attributed to electric dipole (ED) and magnetic dipole (MD) interaction with molecular chirality. However, this approach falls short for large molecules that support high-order multipolar components, such as electric quadrupole (EQ) moment. Here, we introduce a theoretical model to study the chiral absorption of large molecules in the presence of plasmonic nanostructures. This model considers both ED–MD interaction and ED–EQ interaction enhanced by a resonant structure. We numerically study such interactions of the chiral molecular solution in the vicinity of an achiral plasmonic nano-resonator. Our results show the distinct spectral information of the chiral medium on- and off-resonance of the resonator.

Structural and temperature-dependent photoluminescence properties of NaBaBO3:Ce3+,Tb3+ phosphors synthesized using the combustion method

This study explores the structural and temperature-dependent photoluminescence of Ce3+ and Tb3+ doped NaBaBO3 phosphors, synthesized via combustion. Analysis of their crystal structures confirmed excellent alignment with the standard PDF#98–008-0110. Investigation into both room and low-temperature photoluminescence revealed that the dopants have a significant effect on emission spectra. Ce3+-doped samples exhibited excitation peaks at 275 nm and 358 nm, leading to a primary emission at 419 nm, with enhanced low-temperature emission suggesting reduced non-radiative processes. Tb3+-doped phosphors showed excitation from 250 to 377 nm and emissions from blue to deep red, including strong green emission at 550 nm due to 5D4→7F5 transitions. Optimal doping was found at 1 mol% for Ce3+, while Tb3+ showed increased luminescence up to 3 mol%, with concentration quenching observed beyond these points. The study indicates dipole–dipole interactions dominate Ce3+ concentration quenching, whereas Tb3+ involves both electric dipole and quadrupole interactions. This analysis provides insights into enhancing luminescent efficiency and suggests NaBaBO3:xCe3+,Tb3+ phosphors' potential in advancing white LED technology, highlighting their stable luminescent properties at low temperatures.

Temperature-dependent evolution of micromagnetic structure of B20-type Fe1-xCoxGe studied by Mössbauer spectroscopy

The non-collinear magnetic structures hosted in magnets with broken central inversion symmetry, some of which are topologically non-trivial, have unique physical properties and application prospects. This paper presents a detailed study of the temperature evolution of the micromagnetic structures of B20-type Fe1-xCoxGe (x = 0, 0.05, 0.10) polycrystalline samples using 57Fe Mössbauer spectroscopy. We take the relatively weak electric quadrupole interaction as a perturbation of the hyperfine magnetic interaction to obtain the distribution of the hyperfine magnetic field Hhf (φ) in the plane perpendicular to the magnetic propagation vector ks. It is found that the geometric features of Hhf (φ) are sensitive to the relative orientation of ks regarding the electric field gradient at the iron nucleus, as well as to the spin texture. The temperature dependence of Hhf (φ) provides a distinct signal of first-order phase transition when ks shifts from [100] to [111]. The doping of cobalt atoms leads to out-of-plane component and in-plane component aggregation of the neighboring iron magnetic moments. These results are instructive for understanding the dynamical behavior of spiral magnets with long-periods.

The germanides ScTGe2 (T = Fe, Co, Ru, Rh) – crystal chemistry, 45Sc solid-state NMR and 57Fe Mössbauer spectroscopy

Abstract The TiMnSi2-type (space group Pbam) germanides ScTGe2 (T = Fe, Co, Ru, Rh) were synthesized from the elements by arc-melting. Single crystals were grown by annealing sequences of the arc-melted buttons in an induction furnace. The structures of ScFeGe2, ScRuGe2 and ScRhGe2 were refined from single-crystal X-ray diffraction data. In ScRuGe2, the ruthenium atoms have distorted octahedral germanium coordination (242–268 pm Ru–Ge). Three trans-face-sharing octahedra form a sub-unit which is condensed via common edges in c direction and connected via common corners with four adjacent blocks, forming a three-dimensional [RuGe2 type] substructure. The two crystallographically independent scandium sites have coordination numbers 15 (Sc1@Ge8Ru4Sc3) and 17 (Sc2@Ge7Ru6Sc4). Electronic band structure calculations for ScCoGe2 and ScRuGe2 show a net charge transfer from the scandium to the transition metal and germanium atoms, leading to a description with polyanionic networks Sc δ+[TGe2]δ−. The two crystallographically independent Sc sites are easily distinguishable by 45Sc magic-angle spinning (MAS)-NMR spectroscopy. Isotropic chemical shift values and nuclear electric quadrupolar interaction parameters were deduced from an analysis of the triple-quantum (TQ)-MAS NMR spectra. The electric field gradient parameters deduced from these experiments are in good agreement with quantum-chemical calculations using the Wien2k code. Likewise, the two crystallographically independent iron sites in ScFeGe2 could be discriminated in the 57Fe Mößbauer spectra through their isomer shifts and quadrupole splitting parameters: δ = 0.369(1) mm s−1 and ∆E Q = 0.232(2) mm s−1 for Fe1 and δ = 0.375(2) mm s−1 and ∆E Q = 0.435(4) mm s−1 for Fe2 (data at T = 78 K).

Modality for estimating NMR relaxation time using perturbed angular correlation in double-photon emission nuclides

T2 relaxation time in magnetic resonance imaging (MRI), which is determined by magnetic dipole interactions, has been employed as a parameter for tumor detection. However, owing to the lack of MRI detection sensitivity, nuclear medicine imaging is currently the basic option for tracking low concentrations of chemical probes. Previous studies utilizing cascade radionuclides have focused on the relaxation due to electric quadrupole interactions. However, magnetic dipole interactions, which are crucial in MRI, remains to be elucidated. In this study, we determined the magnetic relaxation rate by using 111In, a cascade radionuclide used in clinical single-photon emission computed tomography (SPECT) scans. As the angle between the gamma rays from the nuclei is affected by the electrical and magnetic interactions acting on the nuclei, we measured the angular correlation ratio by using eight gadolinium gallium garnet (GAGG) multi-pixel photon counter (MPPC) 8 × 8 array detectors and extracted the magnetic relaxation rate. Consequently, we obtained a rate that increased with the Fe concentration, similar to the T2 relaxation rate, although it was influenced by the inhomogeneity of the external magnetic field. This study utilized low concentrations of the liquid-state radionuclide, which is commonly used in clinical nuclear medicine imaging scans and is expected to provide much higher sensitivity and more selective detection of tumors than conventional MRI.

Doping level dependence of the structure and luminescence properties of LaBO3: Tb3+ phosphors

Tb3+ doped LaBO3 phosphors with various doping levels were synthesized by hydrothermal and post-calcination methods. The structure, morphology, chemical composition, and optical properties of the samples were studied by X-ray diffraction (XRD), Scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), Electron paramagnetic resonance (EPR), Photoluminescence spectroscopy (PL). XRD patterns reveal that Tb3+ doped LaBO3 crystals with monoclinic or orthorhombic structures can be obtained by adjusting the doping content of Tb3+. The XPS and EDS results indicate that the elements of La, O, B, and Tb were uniformly distributed in the samples, and some doping Tb3+ were oxidized to Tb4+. The prepared Tb3+ doped LaBO3 phosphors emit green emission at 543 nm under 271 nm excitation. The luminescence intensity is affected by the Tb3+ doping level, and concentration quenching will be observed due to an electric quadrupole-electric quadrupole interaction (p-p) process when the Tb3+ doping amount rises above 22 %. In particular, the luminescence properties of the Tb3+ doped LaBO3 phosphors are dramatically affected by the structure of the samples, and the luminescence intensity of the samples with orthorhombic structure is significantly higher than those with monoclinic structure. The decay curves of samples exhibit a double exponential behavior, and the average luminescence lifetime decreases with an increase in Tb3+ doping levels.

Photoluminescence/cathodoluminescence properties and energy transfer mechanisms of fine-particle Gd2O2S:Tb3+, RE3+ (RE = Dy, Eu) phosphor

Gd2O2S:Tb3+, RE3+ (RE = Dy, Eu) phosphors were prepared by molten salt method and the samples were characterized by XRD, SEM, photoluminescence, cathodoluminescence and thermal stabilization. XRD results indicated that phosphors were pure hexagonal crystal structure and Dy3+ and Eu3+ sensitizers successfully occupied the Gd3+ sites. Granularity test results indicated that the average particle size of the powder was 2 μm. The effect of Eu3+ sensitizer on Tb3+ luminescence was discussed for the first time in the photoluminescence spectra. The results verified that the efficient emission of Tb3+ was sensitized by Dy3+/Eu3+ under the excitation of 288 nm/296 nm. 382 nm, 415 nm and 438 nm, which correspond to the 5D3 → 7FJ (J = 6, 5 and 4) of Tb3+, respectively, and 488 nm, 544 nm, 587 nm, 622 nm, which correspond to the 5D4 → 7FJ (J = 6, 5, 4 and 3) of Tb3+, respectively. There was also a weak emission peak of Dy3+ was seen at 576 nm (4F9/2 → 6H13/2) in Gd2O2S:Tb3+, Dy 3+. And weak emission peaks of Eu3+ were seen at 617 nm and 625 nm (5D0 → 7F2) in Gd2O2S:Tb3+, Eu 3+. The sensitizers of Dy3+ and Eu3+ not only effectively enhanced the photoluminescence of Tb3+ through electric quadrupole-electric quadrupole interactions and electric dipole-electric quadrupole interactions, respectively, but also effectively improved the thermal stability of Gd2O2S:Tb3+ through energy transfer. Increasing acceleration voltage could further enhance the powder's cathodoluminescence. Gd2O2S:Tb3+, Dy3+ phosphor had higher cathodoluminescence properties.

Energy transfer of Eu2+→Eu3+ improves the photoluminescence properties of orange-red phosphor La2O2S:Eu

Red phosphor with excellent performance plays an important role in improving the luminous performance of white LED(w-LEDs). In this work, a novel type of orange-red phosphors La2-xO2S:xEu(2+,3+) (0.01 ≤ x ≤ 0.08, ∆x = 0.01) for white LED were synthesized via high-temperature solid-state method, and the phase, morphology, luminescent properties, and thermal stability of the samples were systematically studied. The samples all belong to hexagonal crystal system, and the space group are all P-3m1 (164). Through XPS analysis, it was found that Eu2+ and Eu3+ coexist in La1.96O2S:0.04Eu(2+,3+) phosphor. The energy transfer between Eu2+ and Eu3+ was realized, and the fluorescence intensity increased by 418.03 %. The optimal doping concentration of Eu ions in La2-xO2S:xEu(2+,3+) phosphors is x = 0.04, and the concentration quenching mechanism is the electric quadrupole electric quadrupole (q-q) interaction. La1.96O2S:0.04Eu(2+,3+) phosphor has excellent thermal stability，the fluorescence intensity still remains 82.67 % at 418 K compared with room temperature, the activation energy Ea= 0.3961 eV, and the trap theory was used to explain the mechanism of thermal quenching. La1.96O2S:0.04Eu(2+,3+) phosphor has high luminescence quality with color purity of 87.08 %. These results show that La1.96O2S:0.04Eu(2+,3+) phosphor has certain application value in the field of white LED phosphors.

Third-harmonic scattering optical activity: QED theory, symmetry considerations, and quantum chemistry applications in the framework of response theory.

In this work, expressions for the third-harmonic scattering optical activity (THS-OA) spectroscopic responses are derived by combining molecular quantum electrodynamics (QED) and response theory, allowing their computational implementation. The QED theory of THS-OA presented here is meant to be an extension of a previous study by Andrews [Symmetry 12, 1466 (2020)]. In particular, the THS-OA phenomena are described within the Power-Zienau-Woolley multipolar Hamiltonian by including the electric-dipole, magnetic-dipole, and electric-quadrupole interactions for the absorption as well as the emission processes between the dynamic electromagnetic field (the photons) and matter. Moreover, we derive the expressions for the differential scattering ratios as a function of the scattering angle defined by the wavevectors of the incident and scattered photons. We show how the pure and mixed second hyperpolarizabilities can be obtained in the framework of response theory as specific cases of a generic cubic response function, thus enabling the computational implementation of THS-OA spectroscopy. We prove the origin-independence of the theory for exact wavefunctions. Preliminary computations on a prototype chiral molecule (methyloxirane) are considered together with an analysis of the basis set convergence and of the origin-dependence.

Strong chiral optical force for small chiral molecules based on electric-dipole interactions, inspired by the asymmetrical hydrozoan Velella velella

Drawing inspiration from a remarkable chiral force found in nature, we show that a static electric field combined with an optical linlin polarization standing wave can exert a chiral optical force on a small chiral molecule that is several orders of magnitude stronger than other chiral optical forces proposed to date, being based on leading electric-dipole interactions rather than relying on weak magnetic-dipole and electric-quadrupole interactions. Our chiral optical force applies to most small chiral molecules, including isotopically chiral molecules, and does not require a specific energy-level structure. Potential applications range from chiral molecular matter-wave interferometry for precision metrology and tests of fundamental physics to the resolution of enantiomers for use in chemistry and biology.

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.

Hyper-Rayleigh scattering optical activity: Theory, symmetry considerations, and quantum chemistry applications.

This work reports on the first computational quantum-chemistry implementation of the hyper-Rayleigh scattering optical activity (HRS-OA), a nonlinear chiroptical phenomenon. First, from the basics of the theory, which is based on quantum electrodynamics, and focusing on the electric dipole, magnetic-dipole, and electric-quadrupole interactions, the equations for the simulation of the differential scattering ratios of HRS-OA are re-derived. Then, for the first time, computations of HRS-OA quantities are presented and analyzed. They have been enacted on a prototypical chiral organic molecule (methyloxirane) at the time-dependent density functional theory level using a broad range of atomic orbital basis sets. In particular, (i) we analyze the basis set convergence, demonstrating that converged results require basis sets with both diffuse and polarization functions, (ii) we discuss the relative amplitudes of the five contributions to the differential scattering ratios, and (iii) we study the effects of origin-dependence and derived the expression of the tensor shifts and we prove the origin-independence of the theory for exact wavefunctions. Our computations show the ability of HRS-OA as a nonlinear chiroptical method, able to distinguish between the enantiomers of the same chiral molecule.

Magnetic field induced reentrant multipolar ordering in the distorted kagome-lattice antiferromagnet Dy3Ru4Al12

We report on ultrasonic and magnetocaloric-effect measurements of the hexagonal antiferromagnet ${\mathrm{Dy}}_{3}{\mathrm{Ru}}_{4}{\mathrm{Al}}_{12}$ having a distorted kagome lattice. We observed a pronounced softening of the transverse modulus, ${C}_{44}$, above 30 T applied along [100], indicating an as-yet-unidentified magnetic field induced phase transition. We determined the field-temperature phase diagrams using pulsed magnetic fields up to 55.2 T, applied along [100] and [001]. Optimizing crystal-electric-field parameters within the mean-field approximation, we conclude that the enhancement of the field induced phase-transition temperature is due to electric quadrupolar and magnetic octupolar mediated interactions. We propose that the order parameter of the magnetic field induced phase transitions is the electric quadrupole ${O}_{zx}$, facilitated by octupole-mediated interactions.

Eu2+/Ce3+-doped NaAlSiO4 selective occupation-induced emission structure unit evolution and its luminescence characteristics

NaAlSiO4: xEu2+,yCe3+ blue-red phosphors were prepared by high-temperature melting-icy quenching-heat treatment. The effects of emission structure unit evolution, microstrain, microcrystalline size and selective occupation on the luminescence characteristics of the prepared phosphor were systematically studied by powder X-ray diffraction pattern (XRD) and photoluminescence spectroscopy (PL). In the structure of NaAlSiO4: 2%Eu2+, 2%Ce3+ hexagonal crystalline sodium nepheline, Eu2+ ions occupy the Na+ (II) position to form a EuNa+(II)2+ luminescent structure unit, and Ce3+ ions occupy the Na+ (I) position to form a CeNa+(I)3+ luminescent structure unit. The NaAlSiO4: 2%Eu2+/NaAlSiO4: 2%Ce3+ emits 555 nm yellow-green light/395 nm blue-violet light under the excitation of 354 nm/298 nm, respectively, which is derived from the 5d-4f transition of Eu2+ and Ce3+. There is energy transfer of Ce3+→Eu2+ in the sodium nepheline matrix, of which the transport pathway is m EuNa+(II)2+ ←O←n CeNa+(I)3+ →O→m EuNa+(II)2+, and the transport mechanism is electric quadrode-electric quadrupole interaction, and the energy transfer efficiency reaches 98.6%. The sodium nepheline NaAlSiO4: 2%Eu2+, 2%Ce3+ phosphor with energy level barrier 0.386 eV, possesses good thermal stability. This single-phase aluminosilicate multicolor phosphor has potential application value for WLED illumination and PDP display.

Synthesis and up-conversion luminescence of Ho3+ and Yb3+ co-doped La7P3O18 phosphors

Ho3+ and Yb3+ co-doped La7P3O18 up-conversion phosphors were prepared by a high-temperature solid-state process. XRD results reveal that the samples are mixtures of monoclinic structure La7P3O18 crystals with P21/n space group and minor LaPO4 crystals. UV—Vis DRS results indicate that La7P3O18 crystal is an indirect semiconductor with an optical band gap of 4.10 eV. After 980 nm laser excitation, the Ho3+ and Yb3+ co-doped La7P3O18 phosphors show the characteristic blue (486 nm), green (550 nm), and red (661 nm) luminescence peaks of Ho3+ ions. The peak at 661 nm dominates in the up-conversion luminescence spectra of samples. Meanwhile, with the increase of Ho3+ and Yb3+ doping content, the up-conversion luminescence intensity increases first and then decreases. By increasing the doping contents of Ho3+ and Yb3+ up to 1 at.% and 10 at.%, respectively, concentration quenching may appear by an electric quadrupole– electric quadrupole interaction process. The pumping power dependence of luminescence indicates that the green and red emissions of samples are excited by a two-photon absorption process. The color coordinates of Ho3+ and Yb3+ co-doped La7P3O18 crystals locate in the orange—red region.

Subcycle-resolved strong-field tunneling ionization: Identification of magnetic dipole and electric quadrupole effects

Interaction of a strong laser pulse with matter transfers not only energy but also linear momentum of the photons. Recent experimental advances have made it possible to detect the small amount of linear momentum delivered to the photoelectrons in strong-field ionization of atoms. Linear momentum transfer is a unique signature of the laser-atom interaction beyond its dipolar limit. Here, we present a decomposition of the subcycle time-resolved linear momentum transfer in term of its multipolar components. We show that the magnetic dipole contribution dominates the linear momentum transfer during the dynamical tunneling process while the post-ionization longitudinal momentum transfer in the field-driven motion of the electron in the continuum is primarily governed by the electric quadrupole interaction. Alternatively, exploiting the radiation gauge, we identify nondipole momentum transfer effects that scale either linearly or quadratically with the coupling to the laser field. The present results provide detailed insights into the physical mechanisms underlying the subcycle linear momentum transfer induced by nondipole effects.

Effects of electric quadrupole interactions with tunable atomic mirrors

Recent studies have involved electric quadrupole effects in atoms interacting with the evanescent mode. This type of surface mode is usually produced by the total internal reflection in a dielectric-vacuum atz=0, and its intensity distribution is very close to the outer surface z>0 half-space. Coating the planar surface of a dielectric substrate with multilayer dielectric thin film of different thicknesses provides an enhanced in such evanescent modes. This type of mode can be used purely as an atomic mirror. We show that the use of such elements for atomic optics gives significant enhancement of the evanescent mode magnitude without degrading the quality of the atomic reflection process. In addition, the decay depth of the evanescent mode can be conveniently controlled by design parameters. This property keeps the atom-light interaction timeτ, and thus the probability of decay emission, very low, which means a high degree of coherence property.

Frequency references based on molecular iodine for the study of Yb atoms using the 1S0 - 3P1 intercombination transition at 556 nm.

We used precision spectroscopy to analyze the R(53)24-1, P(49)24-1, and R(95)25-1 lines of molecular iodine (127I2) to establish optical frequency references for the laser cooling of Yb atoms using the 1S0 - 3P1 intercombination transition at 556 nm. A laser frequency instability of < 2 × 10-12 (for 0.01 s < τ < 3000 s, τ is the average time of the measurement) was attained using the observed Doppler-free hyperfine transitions of the iodine lines. The absolute frequencies of the observed 63 hyperfine transitions were determined with an uncertainty of 7 kHz (fractional uncertainty of 1.3 × 10-11). Highly accurate hyperfine constants were determined by fitting the measured hyperfine splittings to a four-term Hamiltonian that includes the electric quadrupole, spin-rotation, tensor spin-spin, and scalar spin-spin interactions with an uncertainty of approximately 1 kHz. The observed hyperfine transitions of molecular iodine provide new frequency references for research using atomic Yb, because these transitions are close to the intercombination transition of Yb at 556 nm.

Multi-molecule imaging and inter-molecular imaging in nuclear medicine

Abstract Multi-molecule imaging and inter-molecular imaging are not fully implemented yet, however, can become an alternative in nuclear medicine. In this review article, we present arguments demonstrating that the advent of the Compton positron emission tomography (Compton-PET) system and the invention of the quantum chemical sensing method with double photon emission imaging (DPEI) provide realistic perspectives for visualizing inter-molecular and multi-molecule in nuclear medicine with MeV photon. In particular, the pH change of InCl3 solutions can be detected and visualized in a three-dimensional image by combining the hyperfine electric quadrupole interaction sensing and DPEI. Moreover, chemical states, such as chelating, can be detected through angular correlation sensing. We argue that multi-molecule and chemical sensing could be a realistic stream of research in future nuclear medicine.