Quadrupole-quadrupole Interaction Research Articles

Visible emission studies by UV light conversion in (Dy3+/Tb3+) ions pair activated zinc-bismuth-barium borotellurite glasses for achieving intense green and white light

Both white light and green emission properties of (Dy3+/Tb3+) ions pair activated zinc-bismuth-barium borotellurite glasses were studied by ultraviolet light (UV:388 and 366 nm) conversion with a focus on down-conversion process. On the dependences of Tb3+ amounts with co-doping of Dy3+, densities of glasses, excitation, emission, area of the integration in percent, decay times, multipolar interactions, and most responsible photometric parameters are investigated in the current work. These co-activated glasses show a broad color production range (450–700 nm) covering of red (∼622 nm), green (∼545 nm), and blue (∼488 nm) colors under the stimulation of UV light wavelengths. The ratio from Yellow to blue emission was analyzed to study the site symmetry of Dy3+ surrounds. With 388 nm of UV radiation, the area of the integrated intensity under the green (Tb3+:545 nm) peak reaches a maximum of 87 %, while it falls under the yellow (Dy3+:575 nm) peak at about 13 %. The decay times of co-activated glasses were found in decreasing order, followed by fitting with a double-exponential function. The Reisfeld and Dexter's energy transfer mechanism confirmed the reduction in Dy3+ emission and its lifetime values through quadrupole-quadrupole interaction (f = 10). Moreover, photometric properties such as relative color temperatures, color coordinates, and color purity were also discussed and compared to discriminate the potentiality of the present fabricated glasses for use in both white light and green-emitting devices.

The crystal structure, energy transfer and tunable luminescence properties of NaLaMgWO6:Tm3+, Eu3+ phosphors

A series of NaLaMgWO6:Tm3+, Eu3+ phosphors with color-tunable emission were successfully synthesized by the solid-state reaction method. The crystal structure, luminescence characteristics and energy transfer of NaLaMgWO6:Tm3+, Eu3+ phosphors have been studied. It is observed that Tm3+ singly doped phosphors exhibit intense blue emission at 484 nm, and Eu3+ singly doped phosphors emit red light at 621 nm. The phosphors co-doped with Tm3+, Eu3+ exhibit fluorescence spectra composed by the characteristic emission peaks of Tm3+ ions and Eu3+ ions. A tunable emission color from blue to red can be obtained by adjusting the ratio of the doping concentration of Tm3+/Eu3+, indicating a significant energy transfer from Tm3+ to Eu3+. The energy transfer mechanism between Tm3+→Eu3+ in the NaLaMgWO6:Tm3+, Eu3+ phosphors is proved to be a quadrupole-quadrupole interaction. These results show that NaLaMgWO6:Tm3+, Eu3+ phosphors may have a potential application in white light emitting diodes.

Electric polarization near vortices in the extended Kitaev model

We formulate a Majorana mean-field theory for the extended JKΓ Kitaev model in a magnetic Zeeman field of arbitrary direction, and apply it for studying spatially inhomogeneous states harboring vortices. This mean-field theory is exact in the pure Kitaev limit and captures the essential physics throughout the Kitaev spin liquid phase. We determine the charge profile around vortices and the corresponding quadrupole tensor. The quadrupole-quadrupole interaction between distant vortices is shown to be either repulsive or attractive, depending on parameters. We predict that electrically biased scanning probe tips enable the creation of vortices at preselected positions. Our results paves the way for the electric manipulation of Ising anyons in Kitaev spin liquids.

Luminescence properties and energy transfer of Ce3+, Tb3+ codoped Ba2GaB4O9Cl Phosphor

In this paper, a series of Ba2GaB4O9Cl:Ce3+,Tb3+ phosphors were synthesized by the conventional high-temperature solid-state reaction. The incorporation of Ce3+ ions as sensitizers significantly enhances the absorption and luminescence intensity of Tb3+ ions in the Ba2GaB4O9Cl phosphor. The energy transfer from Ce3+ to Tb3+ occurs through the electric quadrupole-quadrupole interaction, with an energy transfer efficiency of 48 %. The internal quantum efficiency of Ba2GaB4O9Cl:Ce3+,Tb3+ phosphor is 39.95 % upon 316 nm excitation. At 423 K, the emission intensity of Ba2GaB4O9Cl:Ce3+,Tb3+ can keep 53.28 % of its initial value at room temperature. All these results indicate that the Ba2GaB4O9Cl:Ce3+,Tb3+ phosphor has potential application for white LED.

Luminescence properties and thermal stability of Dy2O3/Sm2O3 doped glass ceramics containing NaBi(WO4)2

Dy2O3–Sm2O3 co-doped transparent glass ceramics (GCs) containing NaBi(WO4)2 crystalline phase were prepared by melt-curing-crystallization method. The optimal heat treatment condition is 580 °C/2 h. The optimum incorporation concentration of Dy2O3 is 0.4%, exceeding which a quenching phenomenon dominated by quadrupole-quadrupole interactions emerges. Meanwhile, when the concentration of Dy2O3 was fixed, the chromaticity coordinate of the sample moved the cool white light region to the warm white light region as the concentration of Sm2O3 increased. The temperature-dependent emission spectra of the 0.4% Dy2O3-0.7% Sm2O3 co-doped GC samples show that emission intensity at 575 nm at 185 °C still reaches 80% of the room temperature. The thermal quenching activation energy was 0.1537 eV and the activation energy after the addition of Mo6+ was 0.1957 eV. This study indicates that Dy2O3–Sm2O3 co-doped GCs containing NaBi(WO4)2 crystalline phase can achieve light-color tunable emission, which is potentially valuable for solid-state color rendering and illumination applications.

Structural and optical properties of Cd2MgTeO6:Dy3+, Na+ phosphors for potential application in w-LEDs and personal identification

Cd2MgTeO6:Dy3+, Na+ phosphors were synthesized via a high-temperature solid-phase reaction. Phase purity, structure, surface morphology, luminescent properties, and thermostability of the samples were analyzed exactly. Under 351 nm excitation, Cd2MgTeO6:Dy3+, Na+ phosphors possessed three emission peaks: 4F9/2-6HJ/2 (J = 15, 13, 11). The phosphors mainly emitted yellow light due to the intensity of 4F9/2-6H13/2 being higher than other energy level transitions. The optimal doping concentration of Cd2MgTeO6:xDy3+, xNa+ phosphor was x = 10 mol% and the mechanism of concentration quenching was the quadrupole-quadrupole interaction. The phosphors possessed good thermostability and high activation energy (Ea = 0.41 eV). The chromaticity coordinate (CIE) coordinates of Cd2MgTeO6:Dy3+, Na+ were located yellow region and were almost the same at different doping concentration. For Cd2MgTeO6: 10 mol%Dy3+, 10 mol%Na+ phosphor, the internal quantum efficiency (IQE) was 20.55% and the cell viability for the cytotoxicity test was bigger than 88.1%. White-light emitting diode (w-LED) was fabricated with an excellent correlated color temperature (CCT = 5340 K) and a high color rendering index (CRI = 88). Cd2MgTeO6:10 mol%Dy3+, 10 mol%Na+ phosphor could display the feature of latent fingerprint (LFP) and lip print (LP) excellently. Hence, the phosphor could excellently apply to the three-level features of latent fingerprint and six characteristics of lip print identification. In general, Cd2MgTeO6:Dy3+, Na+ phosphors have great potential in w-LEDs and personal identification.

Jahn-Teller distortion, octahedra rotations and orbital ordering in perovskites: KScF as a model system.

The KScF perovskite has been used as a model for investigating the relative importance of the Jahn-Teller (JT) lift of degeneracy, the ScF octahedra rotation (OR), and the quadrupole-quadrupole interaction linked to different occupancy of the Sc t subshell in various sites of the unit cell (orbital ordering, OO). The group-subgroup sequence , , , and , supplemented by and , has been explored by using an Gaussian type basis set, hybrid functionals, and the CRYSTAL17 code. The JT lift of degeneracy provides a stabilization about 5 times larger than the sum of the OO and OR effects. The energy gained in the transition from to , consisting in a rotation of the octahedra around the axis, is 1077 E . From to , additional rotations around the and axes are possible, and the Sc electron can occupy a different t orbital, with a total energy reduction of 2318 E . The rotation of the octahedra reduces the strength of superexchange: in going from to the G-AFM stabilization with respect to FM shrinks by a factor 4.

Structural and optical properties of Zn2.95Ga2−xSnO8:xCr3+: An excellent X-ray charging-based persistent phosphor

This study investigates structural and luminescence properties of Cr3+ doped Zn2.95Ga2SnO8 phosphor. XRD analysis determines the phase purity and lattice parameters, while SEM and TEM analysis were utilized to study the particle size and surface morphology of the sample. UV–visible absorption and PL excitation spectra provided information on the excitation bands and the band-gap of both the undoped and Cr3+ doped Zn2.95Ga2SnO8. The optical band-gap of the material decreases upon doping with Cr3+ ions. Analysis of the Racah parameter and Tanabe Sugano diagram highlights a robust crystal field within Cr3+: Zn2.95Ga2SnO8, causing 2Eg level to become the lowest excited state with sharp emission at 699 nm. Concentration quenching at higher Cr3+ concentrations (> 0.6 mol%) is primarily attributed to the quadrupole-quadrupole interactions. Two distinct traps with trap depths at 0.51 eV and 0.73 eV were identified by using thermoluminescence measurement. The material gives persistent luminescence with a decay time of more than 30 min when charged with blue light (420 nm) and an excellent decay time of more than 16 h when charged with X-rays. Notably, this is the first report on X-ray charging-based persistent luminescence in Zn2.95Ga2SnO8. The outstanding persistent luminescence makes this material highly promising for various applications.

A green light emissive LaSr2AlO5:Er3+ nanocrystalline material for solid state lighting: crystal phase refinement and down-conversion photoluminescence with high thermal stability.

The present study reveals the structural and optoelectronic characteristics of a down-converted (DC) green luminous Er3+ doped LaSr2AlO5 phosphor that was produced by employing an efficient and reliable gel-combustion process assisted with urea as a fuel. Using Rietveld refinement of diffraction data, the crystal structure and phase formation were examined. The surface morphology and elemental configuration of the phosphor were analyzed via TEM and EDX spectroscopy, respectively. The band gap of LaSr2AlO5 (5.97 eV) and optimized La0.96Sr2AlO5:4 mol% Er3+ (5.51 eV) classify the optimized sample as a direct band-gap material. The PL peaks located in the visible range corresponding to transitions 2H9/2 → 4I15/2 (406 nm), 2H11/2 → 4I15/2 (520 nm), 4S3/2 → 4I15/2 (550 nm), and 4F9/ 2 → 4I15/2 (665 nm) were revealed by photoluminescence spectroscopy under 377 nm excitation. Above 4 mol% Er3+ doping, concentration quenching was observed, which was controlled by the quadrupole-quadrupole interaction. Based on the findings of the double exponential fitting of lifetime curves acquired from the emission spectra at λex = 377 nm and λem = 550 nm, the average lifetime of the excited levels of considered nanomaterials was estimated. The temperature-dependent emission spectra of the La0.96Sr2AlO5:4 mol% Er3+ sample were collected in the range 298-498 K. The considered phosphor was found to have a high thermal stability as evidenced by the luminous intensity being sustained at 74.29% at 498 K compared to the intensity at ambient temperature (298 K) with an activation energy of 0.1453 eV. The calculated color purity and superb chromaticity coordinates indicates that the phosphors have a high degree of color purity, which further supports its applicability as a green component in solid-state lighting.

Crystal Growth Regulation of Ruddlesden-Popper Perovskites via Self-Assembly of Semiconductor Spacers for Efficient Solar Cells.

The crystal growth and orientation of two-dimensional (2D) perovskite films significantly impact solar cell performance. Here, we incorporated robust quadrupole-quadrupole interactions to govern the crystal growth of 2D Ruddlesden-Popper (RP) perovskites. This was achieved through the development of two unique semiconductor spacers, namely PTMA and 5FPTMA, with different dipole moments. The ((5FPTMA)0.1 (PTMA)0.9 )2 MAn-1 Pbn I3n+1 (nominal n=5, 5F/PTMA-Pb) film shows a preferred vertical orientation, reduced grain boundaries, and released residual strain compared to (PTMA)2 MAn-1 Pbn I3n+1 (nominal n=5, PTMA-Pb), resulting in a decreased exciton binding energy and reduced electron-phonon coupling coefficients. In contrast to PTMA-Pb device with an efficiency of 15.66 %, the 5F/PTMA-Pb device achieved a champion efficiency of 18.56 %, making it among the best efficiency for 2D RP perovskite solar cells employing an MA-based semiconductor spacer. This work offers significant insights into comprehending the crystal growth process of 2D RP perovskite films through the utilization of quadrupole-quadrupole interactions between semiconductor spacers.

Tb3+ and/or Sm3+ doped NaGd(MoO4)2 nanocrystalline transparent glass-ceramics: Preparation, tunable luminescence, and energy transfer

Tb3+ and/or Sm3+ doped SiO2–B2O3–Na2O–ZnO–MoO3-Gd2O3 transparent glass-ceramics containing NaGd(MoO4)2 nanocrystals were successfully prepared by the melt-quenching method and subsequent heat treatment process. The optimal schedule to achieve heat treatment was crystallized at 650 °C for 5 h. The strongest green luminescence (545 nm: 5D4→7F5) was obtained under 376 nm excitation when the Tb2O3-doped amount was 0.3 mol%. A thorough investigation was conducted to explore the mechanism of energy transfer from Tb3+ ions to Sm3+ ions, which is caused by quadrupole-quadrupole interactions. Tb3+-Sm3+ co-doped SiO2–B2O3–Na2O–ZnO–MoO3-Gd2O3 glass-ceramics can achieve green, yellow, and red multi-color tunable luminescence as the amount of Sm2O3 doping changes, which indicates that it holds promising potential in applications such as ultraviolet-transformed white light-emitting diodes and various optical apparatus.

White-light emitting BaAl2O4/CaAl4O7:x% Dy3+ (0 ≤ x ≤ 3) mixed phase nanophosphors synthesized using citrate sol-gel method

Novel mixed phase BaAl2O4/CaAl4O7 (BC) and BC: x% Dy3+ (0 ≤ x ≤ 3) nanophosphors were synthesized by the citrate sol-gel method. The morphology changed as x%Dy3+ varied. The patterns showed that the BC nanophosphors matched well with the monoclinic CaAl4O7 and hexagonal BaAl2O4 structures. Moreover, the structure of BC was not influence by the dopant. The dopant is mainly located in the BaAl2O4 phase. The crystallite sizes were estimated to be in the nanoscale order. The photoluminescence (PL) results showed that the emission was quenched for BC: x% Dy3+ (x > 2.4) be due to the quadrupole-quadrupole interaction. The emission peaks at 325, 482 and (563 and 576) nm were assigned to the bandgap defects of BC, 4F9/2 → 6H15/2 and 4F9/2 → 6H13/2 transitions of Dy3+, respectively. The International commission on illumination (CIE) showed the dopant (Dy3+) had changed the emission color from blue to white. This showed that the BC: x% Dy3+ (1.2 ≤ x ≤ 3) nanophosphors were potential candidates for white-light LEDs.

Quantum interaction between two entangled non point-like objects in the presence of boundaries

We explore, in the framework of linearized quantum gravity, the quantum gravitational quadrupole-quadrupole interaction between two entangled non point-like objects in the presence of both Dirichlet and Neumann boundaries. The results show that, compared to the case without boundaries, the interaction can be either enhanced or weakened depending on the geometrical arrangement of the objects with respect to the boundaries. In the limit when the two-object system is placed very close to the Dirichlet boundary, the near-regime interaction potential is larger than that of the pure vacuum case when the two objects are placed perpendicular to the boundary but smaller when parallel to it, while, in the far regime, such strong and weak relations between potentials are just opposite to that in the near regime. And, there exists a new r^{-2} far-regime behavior of the interaction potential under the perpendicular configuration. For the case of Neumann boundary, the strong and weak relations between the interaction potentials under perpendicular or parallel configurations and the case without boundary are opposite to the Dirichlet circumstance both in the near and far regimes. Besides, the novel r^{-2} far-regime behavior occurs for the parallel rather than perpendicular configuration in the presence of Neumann boundary.

Synthesis, crystallographic structure, down shifting luminescence of Er(III) activated GdSr2AlO5 nanophosphors: An efficient green emitter for solid state lighting

In order to investigate a potential phosphor material for solid state illumination applications, we developed a series of green light emanating Er3+ doped GdSr2AlO5 (GSA) phosphors using the gel-combustion process. Diffraction investigation reveals that the fabricated nanophosphors are of tetragonal symmetry with I4/mcm (140) space group. SEM and TEM micrograph defines the almost smooth, irregular and agglomerated morphology with particle size in nano domain. Calculated band gap energy (5.769 eV) of the optimized sample depicts it's almost semiconductor behaviour. EDX spectral lines affirm the composition and pure synthesis of the prepared nanophosphors. The emission spectra of all doped samples consists of one most intense emission band at 550 nm with 4S3/2→4I15/2 transition and three very less intense bands at 406, 520 and 665 nm with 2H9/2→4I15/2, 2H11/2→4I15/2 and 4F9/2→4I15/2 separately. Due to concentration quenching phenomena, intensity of luminous bands gradually rises with the content of Er3+ doped ions up to 0.04 mol after that it starts to decrease regularly. Electric quadrupole-quadrupole interaction among the dopant ions was accountable for this quenching. Lifetime analysis confirms that the decay time is consistently declines with successive addition of trivalent erbium ions. This was due to the increment in the non-radiative path transitions. Suitable location of CIE point in the green region, high CCT and color purity values of the fabricated GdSr2AlO5:Er3+ phosphors endorse their probable utilization in field of solid state lighting.

SrAlOCl:Bi<sup>3+</sup>@SiO<sub>2</sub> phosphor with broad emission band and its effects on LED optical power and correlated color temperature

Sr3Al2O5Cl2:Bi3+ (SAlOCl:Bi3+)phosphor for broadband emission was made using a solid-state method. From the extensive spectroscopic analysis and theoretical computation, significant conclusions about the origin of the Bi3+ emission were drawn. For the Sr 3 and Sr 1 sites, respectively, the dipole-quadrupole and quadrupole-quadrupole interactions were responsible for the concentration quenching in SAlOCl:Bi3+. The resulting luminescence mechanism demonstrated that the crystallization of Bi3+ at the two sites is what causes the emission from each site. The warm white light emitting diodes (LED) models were built with a 380-nm ultraviolet (UV) chip, SAlOCl:Bi3+, and two other phosphors. Then, the color rendering indeces (CRI) and the correlated color temperature (CCT) were calculated. Particularly, the CRI values ranged from 84.3 to 86.2 under operating currents of 20–50 mA, respectively. The increasing SAlOCl:Bi3+ dosage also heightened particle density, resulting in higher scattering coefficients. High scattering results in improved color coordination (lower color variance). The CRI and luminous flux are reduced as the phosphor SAlOCl:Bi3+ concentration increases more than owing to color loss and energy loss by backscattering and re-absorption. Thus, it is advisable to consider SAlOCl:Bi3+ carefully before applying in production.

SrAlOCl:Bi<sup>3+</sup>@SiO<sub>2</sub> phosphor with broad emission band and its effects on LED optical power and correlated color temperature

Sr3Al2O5Cl2:Bi3+ (SAlOCl:Bi3+)phosphor for broadband emission was made using a solid-state method. From the extensive spectroscopic analysis and theoretical computation, significant conclusions about the origin of the Bi3+ emission were drawn. For the Sr 3 and Sr 1 sites, respectively, the dipole-quadrupole and quadrupole-quadrupole interactions were responsible for the concentration quenching in SAlOCl:Bi3+. The resulting luminescence mechanism demonstrated that the crystallization of Bi3+ at the two sites is what causes the emission from each site. The warm white light emitting diodes (LED) models were built with a 380-nm ultraviolet (UV) chip, SAlOCl:Bi3+, and two other phosphors. Then, the color rendering indeces (CRI) and the correlated color temperature (CCT) were calculated. Particularly, the CRI values ranged from 84.3 to 86.2 under operating currents of 20–50 mA, respectively. The increasing SAlOCl:Bi3+ dosage also heightened particle density, resulting in higher scattering coefficients. High scattering results in improved color coordination (lower color variance). The CRI and luminous flux are reduced as the phosphor SAlOCl:Bi3+ concentration increases more than owing to color loss and energy loss by backscattering and re-absorption. Thus, it is advisable to consider SAlOCl:Bi3+ carefully before applying in production.

Spectroscopic study of cooperative states of Nd3+ pair centers in fluorite-type crystals: A competition of dipole-dipole and quadrupole-quadrupole energy exchange

Pair centers of Nd3+ ions in the CdF2, CaF2, and SrF2 doped crystals at T=6.5K were studied under tunable narrow-linewidth laser excitation. It has been established that the exchange of electronic excitation leads to the splitting of the one-exciton cooperative 4G5/2(1) x 4I9/2(1) state by 2–3 cm−1 with a non-monotonic dependence on the distance between the ions in the pairs in these crystals. This dependence is explained by the competition of forced dipole-dipole and quadrupole-quadrupole interactions with spin flip. The high rate of such exchange mechanisms is due to strong spin–orbit interaction and small energy difference between the 4f levels of Nd3+ ions. It is shown that the pair centers in all one-exciton cooperative states, in contrast to the ground and two-exciton excited states, have nonzero static dipole moments. This makes it possible to use the latter states as ultrafast qubits, and one-exciton states as control qubit to implement a CNOT quantum gate.

Multipole expansion of gravitational waves: memory effects and Bondi aspects

In our previous work, we proposed an algorithm to transform the metric of an isolated matter source in the multipolar post-Minkowskian approximation in harmonic (de Donder) gauge to the Newman-Unti gauge. We then applied this algorithm at linear order and for specific quadratic interactions known as quadratic tail terms. In the present work, we extend this analysis to quadratic interactions associated with the coupling of two mass quadrupole moments, including both instantaneous and hereditary terms. Our main result is the derivation of the metric in Newman-Unti and Bondi gauges with complete quadrupole-quadrupole interactions. We rederive the displacement memory effect and provide expressions for all Bondi aspects and dressed Bondi aspects relevant to the study of leading and subleading memory effects. Then we obtain the Newman-Penrose charges, the BMS charges as well as the second and third order celestial charges defined from the known second order and novel third order dressed Bondi aspects for mass monopole-quadrupole and quadrupole-quadrupole interactions.

Synthesis, structure and luminescence properties of a novel red fluorescent material Ba2MgB2O6:Eu3+

The crystal structure of Ba2-xMgB2O6:xEu3+ phosphors, synthesized using a solid-state reaction, have been confirmed by X-ray diffraction analysis. This study focuses on the site occupancy preference of Eu3+ ions within the matrix, which was determined using bond energy theory, fluorescent spectra, and a consideration of energy transport and decay curves. The impact of Eu3+ ion concentration on luminescence has been assessed, and an optimal concentration (x = 0.22) identified. The critical distance, Rc was 9.6 Å, with a calculated θ value of 19.67, indicating that quadrupole-quadrupole interaction plays a critical role in the quenching Ba2-xMgB2O6:xEu3+ phosphors. The Ba2-xMgB2O6:xEu3+ phosphors exhibited a color purity of 99.26%, and a quantum efficiency of 49.68%. The activation energy Ea was determined to equal 0.2987 eV. The results have established Ba1.78MgB2O6:0.22Eu3+ as a red fluorescent powder with high quantum efficiency and a millisecond fluorescence lifetime.

Improvement of Luminescence Properties of Eulytite Single-Phase White Emitting Ca3Bi (PO4)3: Ce3+/Dy3+ Phosphor.

To reduce the issue of tri-primary color reabsorption, a new approach for single-phase phosphors as light-emitting diodes (LEDs) has been recommended. The structures, morphology, photoluminescence, thermal stability, and luminescence mechanism of a variety of Ca3Bi (PO4)3 (CBPO): Ce3+/Dy3+ phosphors were investigated. XRD characterization showed that all CBPO samples were eulytite structures. Furthermore, the energy transfer process from Ce3+ to Dy3+ in CBPO is systematically investigated in this work, and the color of light can be adjusted by changing the ratio of doped ions. Under UV light, energy is transferred from Ce3+-Dy3+ mainly through quadrupole-quadrupole interactions in the CBPO host, and doping with different Dy3+ concentrations tunes the emission color from blue to white. The thermal stability of the CBPO: 0.04Ce3+, 0.08Dy3+ samples is outstanding, and the CIE coordinates of the samples after emission have little effect with temperature, while their emission intensity at 423 K is as strong as that at room temperature, reaching 90%. The above results indicate that this CBPO material has great potential as a white light phosphor under near-UV excitation at the optimized concentration of Ce3+ and Dy3+.