Intensity Parameters Research Articles

Temperature dependence of Ce luminescence characteristics in LaBr3: Ce crystal

Despite the large interest in the scintillation properties of LaBr3:Ce, a detailed understanding of the underlying mechanism of temperature-dependence properties of Ce luminescence remains elusive. This study introduces a self-designed spectral apparatus to explore these properties in LaBr3:5%Ce. We observed a redshift phenomenon and band changes in the emission peak bands, indicating a reduction of the bond length between Ce and the host with increasing temperature. Moreover, the probability of low-energy peak emission decreases and the probability of high-energy peak emission increases, with increasing temperature was observed, suggesting a correlation with the proximity of Ce's 4f energy level to the valence band. Utilizing intensity parameters from the spectra, we identified the impact of temperature on LaBr3:Ce's self-absorption effect, revealing a significant self-absorption effect at the high-energy peak for the first time. A simple self-absorption model indicated that, despite high quantum efficiency of Ce, the overall self-absorption is minimal, establishing a correlation between the self-absorption coefficient of the high-energy peak and overall absorption. This research offers insights for developing radiation-resistant high-temperature luminescent devices and advances the field of high-temperature luminescent materials.

An extensive inquisition on the impact of modifier oxides over the luminescent properties of Eu3+ embedded Li-Al tri-former glasses for photonic applications

A novel, tri-former glasses with the composition 45B2O3+12P2O5+8SiO2+3Al2O3+10LiF+20MO+1Eu2O3 with varying metal oxides have been fabricated following the melt-quenching technique. The absorption, luminescence and radiative decay measurements were carried out, and the specific colour emitted by the glass sample was determined employing the CIE chromaticity diagram. While monitoring the excitation at 393 nm, luminescence spectra of all the glass samples exhibit red emission pertaining to the 5D0→7F2 transition at around 615 nm. The local geometry around the Eu3+ ions site and the nature of the Rare Earth ion-ligand bond have been analyzed employing Judd-Ofelt theory and the R/O ratio spectral parameter. The intensity parameters follows the trend as Ω2 > Ω4 > Ω6 and the results are co-related well with the R/O ratio spectral parameter values. Radiative properties such as σPE, βR and AR of every glass in the present series possess higher values, and the FWHM exhibits lower value, indicating the potentiality of the BPSAEu:M glasses for lasing applications. Among the prepared samples, BPSAEu:Ba glass exhibit higher values for σPE and AR as 42.3 × 10−22 cm2 and 641.71 s−1 respectively which are apt for laser applications. The quantum yield pertaining to the 5D0→7F2 transition exhibit more than 65 % for all the samples and particularly Barium oxide incorporated glass BPSAEu:Ba exhibits 84 %. The present study suggests that BPASEu:Ba glass is a promising luminescent material for photonic/LED applications.

Assessment of luminescent features on Sm3+ ions doped LiF assimilated lead-free borate glasses for visible photonic and optoelectronic applications

The distinctive set containing Sm3+ ions doped LiF incorporated Alkaline borate glasses have been synthesised via the melt quenching practice. 59B2O3+20LiF+(20–X)CaCO3+XBaCO3 +1Sm2O3 (where X = 5, 10, 15, 20 wt%) is the composition used for the glass preparation. The effect of samarium ions concentration dependency on the absorption and emission of barium and calcium oxide has been studied through several spectroscopic studies. The current set of glasses is ionic, determined by the bonding value. The hypersensitive absorption transition is found in the visible region of the absorption spectra, and the transition from 6H5/2 to 6P3/2 shows the highest oscillator strength of 14.87 × 10−6. The intensity parameters are denoted by Ωλ (where λ = 2,4,6) are assessed and discussed. The results indicate that Ω4 is higher when compared to the other two parameters. The lower Ω2 values further ensure the ionic nature of the glass samples. Moreover, the intensity parameters are utilised to predict some radiative properties for the lasing potential evaluation, which includes cross-sections of emission (σPE), probability of radiative transition (A), and experimental and radiative lifetime (τexp and τR). The decay profile was monitored for the 4G5/2 state, and consistently non-exponential behaviour was observed in all the glasses. Through the CIE colour chromaticity analysis, the CCT (colour-correlated temperature), dominant wavelength, colour, and purity of the emitted light have been evaluated. Concerning all aspects, the glass with 20 wt% of BaCO3 is found to be fit for photonic and optoelectronic applications.

Liver function assessment based on hepatobiliary contrast agent-enhanced magnetic resonance imaging

BACKGROUND: Liver function assessment is very important in clinical practice. The use of magnetic resonance imaging for the anatomical and functional evaluation of the liver is possible in actual clinical practice. AIM: To examine the possibility of using hepatobiliary contrast-enhanced magnetic resonance imaging for the evaluation of liver function. MATERIALS AND METHODS: Datasets of patients who underwent gadoxetic acid-enhanced magnetic resonance imaging were retrospectively reviewed. Patients were divided into two groups: group 1 included patients with impaired liver function, and group 2 included those with normal liver function. Based on magnetic resonance imaging in the hepatobiliary phase, the liver parenchyma signal intensity and its ratio to spleen signal intensity and portal vein signal intensity were estimated. Differences among these parameters were compared between groups. The correlation between liver parenchyma signal intensity and laboratory blood tests reflecting liver function (total bilirubin, albumen, aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, gamma glutamyl transpeptidase, and prothrombin time) were analyzed. RESULTS: Datasets of 53 patients (25 men and 28 women, aged 24–84 years) were analyzed. Group 1 included 19 patients, whereas group 2 included 34. The median liver parenchyma signal intensity was 919.05 [669.65; 1258.35] in group 1 and 1525.13 [1460.5; 1631.4] in group 2 (p=0.0000001). The median ratio of liver parenchyma signal intensity to spleen signal intensity was 1.2 [1.04;1.7] in group 1 and 1.7 [1.46; 1.96] in group 2 (p=0.00076). The median ratio of liver parenchyma signal intensity to portal vein signal intensity was 1.44 [1.29; 1.83] in group 1 and 1.6 [1.43; 1.83] in group 2 (p=0.1). The estimated correlation values between liver parenchyma signal intensity and blood tests parameters were as follows: total bilirubin (r=–0.61; p=0.000001), albumen (r=0.13; p=0.61), aspartate aminotransferase (r=–0.57; p=0.000009), alanine aminotransferase (r=–0.44; p=0.001), alkaline phosphatase (r=–0.45; p=0.0007), gamma glutamyl transpeptidase (r=–0.5; p=0.0003), prothrombin time (r=–0.34; p=0.04). CONCLUSION: The study reflects the ability to assess liver function using indices (liver parenchyma signal intensity and its ratio to spleen signal intensity) derived from gadoxetic acid-enhanced magnetic resonance imaging. However, this study did not confirm the assumed effectiveness of using the liver parenchyma signal intensity to portal vein signal intensity ratio as an index of liver function. A significant inverse correlation was identified between liver parenchyma signal intensity and blood test parameters in reflecting liver function, except for albumin. The results indicate the possibility of using magnetic resonance imaging to assess liver function.

In Search of Covalency Measure of Gd(III)-Ligand Interactions.

Experimental electron density distribution of the [C(NH2)3]3[Gd(EDTA)F2]·H2O crystal was determined. The derived experimental and theoretical (DFT) topological parameters such as ∇2ρc, ρc, bond degree (BD), kinetics, and potential energy were used to study the nature of Gd-O, Gd-F, and Gd-N interactions. The natural charge of the Gd is 1.86; the natural configuration of the cation is [Xe]6s0.134f7.105d0.83, and the covalency of the Gd-L bond is mainly connected with the transfer of charge from the spx ligand orbitals onto the 5d orbitals of the Gd cation. Simultaneously, the donation of charge onto the 6s and 4f orbitals occurs to a lesser extent. Moreover it was found that the donation of the ligand charges onto the Gd(III) is larger for compounds with a lower coordination number. The obtained topological parameters were analyzed in the context of the Gd(III) f-f transition properties, i.e., energy of the excited 2S+1LJ states, Judd-Ofelt intensity parameters, and luminescence lifetimes, of 18 Gd(III) compounds with various O, N, and F donor ligands (DOTA, EDTA, CDTA, DTPA, NTA, EGTA, ODA, F-, H2O, and CO32-). The calculated nephelauxetic β parameter may reflect the penetration degree of electron lone pairs of ligands inside the metal basin. Finally, it was found for the first time that the sum of the Gd(III)-L bond energy (∑EGdL) is correlated with the position of the gravity center of the 8S7/2 → 2S+1LJ transitions and increase of covalency of the Gd(III)-L bonds is associated with decrease of their bond energy. The obtained results may shed light on chemical bonding in systems containing f-elements. Such subtle differences in the covalent contribution to the Ln-L or An-L bond may tune the selectivity of the partitioning processes of lanthanides and actinides.

Analysis of spectroscopic characteristics of Sm3+ ions doped gallium silicate glasses for orange-red LEDs

In this work, a variety of Sm3+ ions doped gallium silicate glasses have been made using the conventional melt quenching procedure, and characterized by X-ray diffraction, absorption spectrum, fluorescence spectrum, fluorescence decay curves, respectively. The density of the glass increases with the increase of the concentration of Sm3+ ions, and XRD shows that the samples are all amorphous glasses. Absorption spectra were used to determine the J-O intensity parameters (Ωλ, λ = 2, 4, 6), as well as the radiation transition probability(A), fluorescence branching ratio(βr), and radiation lifetime(τr) of Sm3+ ions at the 4G5/2 energy level. Under 403 nm excitation, the emission spectra show obvious emission peaks at 602 nm and 649 nm, corresponding to 4G5/2 → 6H7/2 and 4G5/2 → 6H9/2 transitions respectively. The B3 glass sample has the largest emission cross section(σem) at the 4G5/2 → 6H7/2 transition, with σem = 11.40 × 10−22 cm2. The color coordinates, color purity and color temperature values of all samples were calculated. The color purity of all samples varied in the range of 96.20%–99.14 %, with the relevant samples separating in the orange-red light region. The experimental results indicate that the glass samples have a potential application prospect in the field of orange-red LEDs.

Spectroscopic analysis of La2(WO4)3:Tb3+ phosphor and the delayed concentration quenching of 5D4 →7FJ emission

Trivalent terbium ion doped lanthanum tungstate (La2-xTbx(WO4)3; x = 0.6,1.0,1.4) and terbium tungstate (Tb2(WO4)3) phosphors were successfully synthesized via optimized microwave-assisted co-precipitation technique. The phase purity and crystallinity of the prepared samples were confirmed using the powder XRD technique. The photoluminescence studies revealed a quenching-free emission up to 70 % of Tb3+ doping concentration, even though the emission intensity slightly decreases under host excitation since it becomes less relevant at higher doping concentrations. The experimental and calculated oscillator strengths were evaluated using absorption data and further used to quantify the Judd - Ofelt (JO) intensity parameters, which appeared in a trend of Ω2>Ω4>Ω6 for all samples. As a theoretical approach to assure the excellency of the tungstate host, the radiative parameters were calculated from the emission data using the JO analysis technique. The dominance in the values of stimulated emission cross section and gain bandwidth corresponding to 5D4→7F5 transition of Tb3+ ion of lanthanum tungstate proclaims it as an excellent green phosphor. Hence, the less susceptibility of the tungstate host towards concentration quenching is confirmed in the present work.

QPOs and circular orbits around black holes in Chaplygin-like cold dark matter

Understanding the nature of dark energy in the universe is an actual issue in theoretical astrophysics and cosmology. One way to do it is by probing dark fluids with different equations of states (EoS). In the present work, we consider a Schwarzschild black hole (BH) surrounded by a dark fluid with a Chaplygin-like EoS as a generalized version of the Chaplygin EoS. We first investigate the effects of the dark fluid parameters on the horizon properties of the BH. The effective mass of the spacetime is calculated and analyzed under the dark fluid parameters. The scalar invariants of the BH spacetime are also calculated, and it is shown that the spacetime curvature increases as the dark fluid parameter increases. Next, we studied the circular motion of the test particle around the BH. As standard particle motion investigations, we analyze the effective potential of the particles for circular motion, specific energy, and angular corresponding to circular orbits with zero and nonvanishing values of the dark fluid intensity. In addition, we study the innermost stable circular orbits (ISCO). It is observed that there is an outermost stable circular orbit (OSCO) due to the presence of the dark fluid. It also shows that at a critical value of the dark fluid intensity parameter, ISCO and OSCO take the same radius. We calculate the frequency of Keplerian orbits and radial and vertical oscillations of the particles along stable circular orbits. We also applied orbital data from hotspots observed near Sgr A* to obtain upper and lower values for the EoS parameter. Finally, we investigate quasiperiodic oscillations and obtain the mass-to-EoS parameter relations for GRS J1915-105 and XTE 1550-564.

Relating Quartz Crystallographic Preferred Orientation Intensity to Finite Strain Magnitude in the Northern Snake Range Metamorphic Core Complex, Nevada: A New Tool for Characterizing Strain Patterns in Ductilely Sheared Rocks

AbstractDocumenting the magnitude of finite strain within ductile shear zones is critical for understanding lithospheric deformation. However, pervasive recrystallization within shear zones often destroys the deformed markers from which strain can be measured. Intensity parameters calculated from quartz crystallographic preferred orientation (CPO) distributions have been interpreted as proxies for the relative strain magnitude within shear zones, but thus far have not been calibrated to absolute strain magnitude. Here, we present equations that quantify the relationship between CPO intensity parameters (cylindricity and density norm) and finite strain magnitude, which we calculate by integrating quartz CPO analyses (n = 87) with strain ellipsoids from stretched detrital quartz clasts (n = 49) and macro‐scale ductile thinning measurements (n = 7) from the footwall of the Northern Snake Range décollement (NSRD) in Nevada. The NSRD footwall exhibits a strain gradient, with Rs(XZ) values increasing from 5.4 ± 1.4 to 282 ± 122 eastward across the range. Cylindricity increases from 0.52 to 0.83 as Rs increases from 5.4 to 23.5, and increases gradually to 0.92 at Rs values between 160 and 404. Density norm increases from 1.68 to 2.97 as Rs increases from 5.4 to 23.5, but stays approximately constant until Rs values between 160 and 404. We present equations that express average finite strain as a function of average cylindricity and density norm, which provide a broadly applicable tool for estimating the first‐order finite strain magnitude within any shear zone from which quartz CPO intensity can be measured. To demonstrate their utility, we apply our equations to published data from Himalayan shear zones and a Cordilleran core complex.

Effects of Rainfall Intensity, Kinetic Energy and Slope Angle to the Upslope, Downslope, and Lateral Slope Components of Splash Erosion in Hillslope Agriculture: A Case in Badiangan, Ajuy, Iloilo

This study was conducted in Barangay Badiangan, Ajuy, Iloilo City, Philippines (11°10’N, 122°58’E) to determine the effects of rainfall intensity and other rainfall-derived parameters on the directional components of splash erosion in hillslopes. There are five experimental set-ups with slope angles ranging from 0% to 48% were tested under natural rainfall conditions using a modified splash collector. The data collected shows that kinetic energy, slope, and rainfall intensity have shown significant effects on splash erosion. The models obtained using regression analysis are 𝑄𝑄𝑑𝑑𝑑𝑑𝑑𝑑=0.0093(𝐾𝐾𝐾𝐾0.80) and 𝑄𝑄𝑡 𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡=0.060(𝐾𝐾𝐾𝐾0.107)(𝑆𝑆0.700)(𝐼𝐼200.700) . The model equation performance has been validated using the Standard Error of Estimates with values of 12 and 9.4 for splash detachment and splash transport, respectively. The constants used for kinetic energy in detachment and slope in transport align with the research by Quansah (1981) for sandy soil, which is similar (the characteristics) to the soil at our research site. Additionally, rainfall intensity, especially with a 20-min duration, generated the best model as it yielded the lowest SEE value for all cases.

Particle shape descriptors as a tool for classification of grain breakage

This study explores particle breakage of a calcareous sand, utilising dynamic image analysis and direct shear tests at varying normal stress levels to analyse the sand crushing mechanism. Tests were arrested at four phase transition points encountered during shear. Particle breakage was traced along a proposed scale based on the literature. Distinct behaviours in shape descriptors for particles of different diameters were observed under changing stress conditions. Agglomerated particle-level behaviour indicates that applied stress levels lead to different soil responses; at low stress, grains roll or slide, whereas at high stresses, grain movement is restricted. Particle breakage was evident even at minimal stress, with increasing grain size reduction as shear strain and stress levels heightened. This study introduces a parameter loading intensity (LI), amalgamating the effects of force chains and loading duration to model grain crushing. Relationships among the shape-angularity group indicator (SAGI), convexity (Cx) and sphericity (S) were also established, enabling calculation of these descriptors, after any loading intensity is applied, based on the initial values. Finally, a methodology for forecasting changes in S and Cx, under any given LI for materials with a known SAGI is presented.

The influence of Ho3+ ions on the optical and luminescence properties of fluoro borosilicate (SBNC) glasses for green laser applications

The holmium (Ho3+) ions-based fluoro borosilicate (SBNCHo) glasses have been prepared using the traditional melt quenching technique with varying concentrations of Ho3+ ions. Physical parameters were analyzed using x-ray diffraction, energy dispersive analysis of x-rays, fourier transform infrared spectroscopy, optical, luminescence, and Commission International de I'Eclairage (CIE) studies. Judd-Ofelt spectral intensity parameters were evaluated for SBNCHo_1.0 (Ω2 = 5.292 x 10-20 cm2, Ω4 = 3.062 x 10-20 cm2 and Ω6 = 3.376 x 10-20 cm2) glass, optical bandgaps were estimated using optical absorption studies. The Photoluminescence emission spectra were recorded for synthesized glasses with 452 nm excitation. The stimulated emission (σe = 1.40 x 10-20 cm2) for the intense green radiation (5S2 (5F4) → 5I8) was calculated. The lifetime decay profile was analyzed for all the synthesized glasses. From the CIE color coordinates of SBNCHo glasses, the color purity was estimated to be (SBNCHo_1.0 (98.6 %)). These results strongly support the applicability of SBNCHo_1.0 glass for green laser applications.

Spectroscopic investigation of co-formers on Dy3+ ions activated Barium comprised zinc borate glasses for enhancing the solid-state laser applications

The purpose of the existing research is to analyze the luminescence behavior on a set of different co-formers involved Dy3+ ions activated Barium comprised zinc borate glasses fabricated through the utilization of usual melt quenching technique with a glass composition of 64B2O3+20ZnF2+15BaO+1Dy2O3 & 44B2O3+20A+20ZnF2+15BaO+1Dy2O3 (where A = 0, P2O5, TeO2, Bi2O3). Their structural, optical, luminescence and decay behavior were scrutinized by several respective characterization techniques. Some of the physical properties were calculated by utilizing the corresponding formulae. Besides, the bonding parameter and oscillator strength estimation alongside Judd-Ofelt parameter are also computed to find out the radiative properties from luminescence spectra. From these analyses, ionic nature of the glass network was confirmed. The spectroscopic intensity parameter follows the tendency Ω2>Ω6>Ω4. This higher value of Ω2 is owing to the larger oscillator strength value and signalizing that Dy3+ ions are completely doped into the glass network. Among all the as- quenched samples, BZfBaT:Dy glass possesses high stimulated emission cross-section and holds high optical gain width value which implies that the glass is a perfect candidate intended for laser utilization. By utilizing its emission spectra, the colour chromaticity coordinates (x, y), colour purity, colour correlated temperature (CCT), and Y/B intensity ratio were investigated by means of CIE 1931 diagram and confirmed the light emitting capability. Decay curve displays well-fitting with the exponential fit and the efficiency (ɳ) for the BZfBaP:Dy glass is found to be 61 % and possesses high optical gain signalizing that the material is a perfect choice for optoelectronic applications.

Effects of Longitudinal Alternating Magnetic Field on the Microstructure and Properties of CMT-WAAM Al-5%Mg Alloy

The major challenges in wire arc additive manufacturing (WAAM) of aluminum alloys include improving the forming quality, reducing pore and crack defects, and optimizing the overall mechanical properties. In this study, an external longitudinal alternating magnetic field (LAMF) was applied to assist cold metal transfer (CMT) WAAM process of Al-5%Mg alloy. This study compared the effects of different LAMF intensity parameters on the electrical behavior, molten droplet transition, macroscopic forming, microstructure and mechanical properties of CMT-WAAM multi-layer thin-walled structures. Compared with the situation without the alternating magnetic field, the application of an external LAMF could cause the arc to expand and rotate, deflect droplets and stir the molten pool periodically. When the alternating magnetic field parameters were set at a current of 3A and frequency of 100Hz with magnetic field intensity of 9mT, the deposited samples achieved macroscopic forming with superior surface quality and geometric accuracy, and the internal defect rate was reduced from 0.742% to 0.168%. Also, the mean grain size of the deposited layer was reduced from 186μm to 154μm, and the average hardness was increased from 68.1HV0.2 to 91.1HV0.2 with an improvement rate of 33.7%. Moreover, the longitudinal tensile strength was increased from 249 MPa to 257 MPa, the transverse tensile strength was increased from 264 MPa to 273 MPa, and the yield strength and elongation at break were both increased. This study demonstrates theoretical guidance for enhancing the component overall performance of aluminum alloy LAMF-WAAM technology.

Effect of Shot‐Peening Process and Nanoparticle‐Added Lubricant on the Tribological Performance of Aluminium‐Based Sliding Bearing Material

ABSTRACTIn this study, it is aimed to increase the wear and fatigue performance of aluminium‐based sliding bearing material by using silver nanoparticles (AgNPs) added lubricant and shot‐peening process. The main purpose is to minimise the wear of the bearing material by penetrating AgNPs added lubricants into the rough surfaces formed by shot peening. Almen intensity, coverage and shot size parameters in the shot‐peening process were analysed in terms of hardness, surface roughness and fatigue strength. The shot‐peened aluminium bronze was subjected to wear experiments under dry, pure water and AgNPs added lubricant conditions. The wear test results were analysed in terms of friction coefficient, wear volume and surface roughness parameters, and the interaction of lubricant and shot‐peening parameters was evaluated. According to the results of the shot‐peening experiments, the Almen intensity was the most effective parameter in terms of hardness and surface roughness (91.62%). It was concluded that the hardness value was 8% higher at high Almen (12–14A) intensity compared with low Almen intensities, and the shot‐peening process could increase the fatigue strength by ~21 times. According to the wear tests, the most effective parameters were 4–6 Almen intensity and AgNP‐added lubricant.

Current problems of special strength training in thai boxing at the beginning stage for athletes of different age categories

The presented work reveals the essence of one of the important problems of the modern system of special strength training in Thai boxing and other types of mixed martial arts, which is connected with various ratios in the process of classes at the stage of initial training of people of different age categories, which complicates the process of developing a single model of training classes without taking into account age-related features of the body's adaptation to loads. It was established that coaches with 5±0.7 years of work experience give priority to the training of children aged 8-12 years in order to achieve success in sports activities in the future. At the same time, trainers with 16±2.5 years of experience believe that mastering an effective tactical and technical arsenal for self-defense is one of the main reasons for practicing Thai boxing for several age categories (representatives of youth and mature age). It was found that with increasing experience, coaches pay more attention not only to the problems related to the determination of optimal parameters of volume indicators, load intensity and development mechanisms, correction of appropriate training regimes, but also to issues that complicate the system of control and management of the adaptation processes of the athletes' body. onsets of different age categories to a stressful physical stimulus.

An Investigation of the Photonic Application of TeO2-K2TeO3-Nb2O5-BaF2 Glass Co-Doped with Er2O3/Ho2O3 and Er2O3/Yb2O3 at 1.54 μm Based on Its Thermal and Luminescence Properties.

A glass composition using TeO2-K2TeO3-Nb2O5-BaF2 co-doped with Er2O3/Ho2O3 and Er2O3/Yb2O3 was successfully fabricated. Its thermal stability and physical parameters were studied, and luminescence spectroscopy of the fabricated glasses was conducted. The optical band gap, Eopt, decreased from 2.689 to 2.663 eV following the substitution of Ho2O3 with Yb2O3. The values of the refractive index, third-order nonlinear optical susceptibility (χ(3)), and nonlinear refractive index (n2) of the fabricated glasses were estimated. Furthermore, the Judd-Ofelt intensity parameters Ωt (t=2,4,6), radiative properties such as transition probabilities (Aed), magnetic dipole-type transition probabilities (Amd), branching ratios (β), and radiative lifetime (τ) of the fabricated glasses were evaluated. The emission cross-section and FWHM of the 4I13/2→4I15/2 transition around 1.54 μm of the glass were reported, and the emission intensity of the visible signal was studied under 980 nm laser excitation. The material might be a useful candidate for solid lasers and nonlinear amplifier devices, especially in the communications bands.

Characterization and Properties of ZnO:Nd<sup>3+</sup> Nanomaterial Synthesized by Chemical Synthesis Method

Nd3+ ion-doped ZnO nanomaterial was prepared using chemical synthesis method and its fluorescence spectra have been investigated at room temperature. From SEM images of the synthesized ZnO: Nd3+ nanoparticles it is observed that an increase in concentration of Nd3+ ions leading to the decrease in the particle size. Nearly hexagonal shapes for the dark spots in the SAED images indicate that the ZnO nanoparticles are almost hexagonal. The oscillator strengths leading to 4f ↔ 4f transitions are characterized by different Judd-Ofelt intensity parameters Ωλ (λ = 2, 4 and 6). These Ωλ parameters along with the fluorescence data and various radiative properties viz., spontaneous emission probability (A), radiative life time (t), fluorescence branching ratio (b) and stimulated emission cross-section (sp) were evaluated and compared with the reported values. The values of these parameters indicate that the observed transitions 4F3/2 → 4I11/2, 4F3/2 → 4I13/2 and 4F3/2 → 4I15/2 can be considered to be good laser transitions in the near infrared region for different optoelectronic and spintronic uses.

Structure and photoluminescence properties of coordination compound [Eu2(o-MBA)6(phen)2] with high quantum yield

An europium(III) coordination binuclear compound [Eu2(o-MBA)6(phen)2] (o-MBA = ortho-methylbenzoate, phen = 1,10-phenantroline) has been synthesized and investigated by X-ray diffraction method, thermogravimetric analysis (TGA), infrared (IR) and photoluminescence (PL) spectroscopy. The single crystal X-Ray diffraction measurements show that the compound crystallizes in the triclinic centrosymmetric space group P-1. The PL excitation spectrum displays a broad band between 300 and 420 nm and a number of sharp transitions between 384 and 590 nm, which can be attributed to the Eu3+ 4f6 intra-shell excitation transitions. The complex exhibits characteristic narrow, metal-centred emission bands, which are determined by the radiative transitions of the Eu3+ ion, from the first excited non-degenerate 5D0 level to the 7FJ (J = 0–4) manifold. The compound shows intense hypersensitive transition 5D0→7F2 which dominates the PL emission spectrum. The dipole strengths of the transitions were determined from the emission spectra in terms of Judd-Ofelt (JO) intensity parameters Ωλ (λ = 2, 4). The high intensity bright-red emission of the complex can be attributed to highly polarizable ligands environment and the low site symmetry (Ci) around the lanthanide ions. We suppose that the J-mixing effect in the Eu(III) ions is responsible for enhanced peak maximum of the 5D0→7F0 transition.

Judd-Ofelt analysis of dimeric europium carboxylates with gradually changing distortions of the crystal field around Eu3+ ion

Experimental and theoretical Judd-Ofelt intensity parameters Ωλ, rates of radiative Arad and nonradiative Anrad processes, and quantum efficiency of luminescence were calculated for a series of related aromatic and aliphatic carboxylates [Eu2(RCOO)6L2] (L - 1,10-phenanthroline or 2,2′-bipyridine) using the LUMPAC software. The behavior of these characteristics in the sequence of europium carboxylates with the gradually changing distortions of the crystal field, which is mainly caused by variation in the bond lengths of the bridging-cyclic COO− groups with Eu3+ ion, was analyzed. A correlation between the changes in the value of the Ω2 intensity parameter, the radiative rate Arad, and the ratio of metal-ligand bond lengths in the Eu coordination polyhedron was demonstrated. The dependence of the parameter Ω2 on the distribution of metal-ligand orbital overlap among Eu-ligand bonds of the compound was revealed. The higher Ω2 values in the set of aromatic carboxylates are associated with a more distorted nearest environment of the Eu3+ ion which is caused by the influence of the bulky R fragments. It is shown that the intensity of f-f transitions of the Eu3+ ion in the compounds under investigation is determined foremost by the dynamic coupling (DC) mechanism. The contribution of this mechanism to the parameters Ω2 and Ω4 is close to 100 %, its contribution to the Ω6 parameter is 85–92 %. The luminescence quantum efficiency for the studied europium carboxylates varies in the range of 52–74 %.