Radiative Transition Probabilities Research Articles

Spectroscopic properties of Pr3+-doped Titania-Silicate glass ceramic for photonic applications

Silicate-Titania (SiTi) glass-ceramics doped with Pr3+ (0.6, 1.6, 2.4 and 3.6 mol%) ions were prepared by sol-gel technique. The materials were characterized by powder XRD, FTIR, TEM, EDX, Optical absorption and Photoluminescence spectroscopy. The identification of non-bridging oxygen (NBO) formation and the removal of OH groups are validated through analysis of the FTIR spectra. Additionally, measurements using XRD and TEM showed that the samples contain nano-sized crystallites. The three phenomenological Judd–Ofelt (J–O) intensity parameters Ω2, Ω4, and Ω6 were obtained and used to analyze different radiative characteristics for the fluorescence levels of Pr3+ in the glass ceramic, including radiative lifetime, branching ratio, radiative transition probability and stimulated emission cross-section. Several emissions were observed in the visible region, among which the 1D2→3H4 in the orange-red region is the most intense. All of these reported branching ratios, stimulated emission cross-sections, and visible emission spectra point to the possibility of employing them as red region lasers. The CIE chromaticity coordinates from all of the emission spectra were also assessed to determine if these materials are suitable for orange-red phosphors. According to CIE chromaticity investigations, 1.6 mol% of Pr3+ ion concentration is ideal for SiTiPr glass-ceramic for use as red phosphors and possibly red lasers.

Temperature-dependent law of transition probability associated with main emission states in YVO4:Re3+ (Re3+=Sm3+, Dy3+ and Eu3+)

The understanding of how radiative transition probabilities change with temperature is crucial for comprehending the relationship between fluorescence behavior and temperature. However, although various models have been proposed to explain the patterns of transition probabilities (A) with temperature changes, they lack consistency due to their derivation from distinct microscopic perspectives. In this study, the macroscopic law of the temperature-dependent A for the 4G5/2, 4F9/2, and 5D0 energy states in YVO4:Re3+(Re3+=Sm3+, Dy3+ and Eu3+) was obtained. Three rare earth ions (Re3+) were identified for each with unique energy level properties conducive to validating the general rules of A. These ions share a common characteristic: in the visible spectrum, their main emissions originate from the radiative transitions from the same higher energy level (4G5/2 in Sm3+, 4F9/2 in Dy3+, and 5D0 in Eu3+) to lower energy levels, respectively. The A of the main emission levels, varying with T, were obtained by fitting the fluorescence decay curves. The exponential law governing non-radiative transitions was revealed after separating the radiative transition rate (WR) from A. The macroscopic law of temperature-dependent transition probabilities of 4G5/2, 4F9/2, and 5D0 energy states in YVO4:Ln3+ (Ln3+ = Sm3+, Dy3+ and Eu3+) has been found to follow the Boltzmann distribution. The results indicate that the non-radiative transitions of the main emission levels of the rare-earth ions are processes from the excited state to adjacent lower energy levels. This macroscopic pattern may serve as a foundational rule for understanding the impact of microscopic factors on A.

Theoretical evaluation on the possibility of laser cooling and simultaneous temperature sensing in Er3+ doped LiYF4 single crystal

In our previous work, a novel laser cooling method was developed using anti-Stokes fluorescence from thermal equilibrium levels of Er3+, with its efficacy proven in Er3+ doped ZBLAN glass. This study has extended the method to Er3+ doped LiYF4 single crystal, where anti-Stokes fluorescence from 2H11/2 is utilized by excitation at the 4S3/2 level of Er3+ for optical in situ temperature control. The non-radiative and radiative transition probabilities among 4f levels of Er3+ were assessed, and the populations of all levels relevant to laser cooling and temperature sensing were calculated. Results demonstrate that the Er3+ doped LiYF4 crystal achieves effective cooling within a specific temperature range, exhibiting high temperature sensitivity.

Theoretical interpretation of W soft X-ray spectra collected by the pulse height analysis system on Wendelstein 7-X stellarator

In many fusion devices, such as tokamaks or stellarators like Wendelstein 7-X (W7-X), soft x-ray pulse height analysis (PHA) system diagnostics are routinely used during the experiments. The PHA system is dedicated to providing information about the impurity content, and average along line-of-sight electron temperature in the plasma conditions. Moreover, it is also able to estimate impurity density and an average effective charge from the comparison of experimental spectra with the modeled ones. However, the experimental x-ray spectra can be interpreted in terms of interesting plasma parameters only when the theoretical radiation models first identify and then take into account all the relevant factors that affect the spectrum. Therefore, for this purpose, a theoretical model has been applied. Flexible Atomic Code, which allows for calculation of various atomic properties such as energy levels, cross sections for excitation and ionization by electron impact, transition probabilities for radiative transitions and autoionization, and any others as needed in the collisional–radiative approximation. The chosen spectra collected during the W7-X campaign (OP1.2b) were examined, trying to obtain an agreement between the observed and simulated spectra. The analysis carried out allowed for a reliable interpretation of experimental x-ray spectra, estimation of the electron temperature, and obtaining information on the content of tungsten impurities.

Spectroscopic studies of Eu doped CaF2 single crystal

The Eu-doped CaF2 crystal is investigated for potential use in visible-region solid-state lasers. The single-crystal Eu: CaF2 has an FCC crystal structure and belongs to the space group Fm-3 m, as confirmed by single-crystal X-ray diffraction. A Raman shift of 324 cm−1 has been observed in a single crystal of Eu: CaF2. The vibrational mode at low frequency is suitable for minimizing non-radiative emissions and increasing radiative emissions. Eu: CaF2 crystal has two absorption bands, at 399 nm and 415 nm, corresponding to the 7F0→5L6 and 7F0→5D3 transitions, respectively. The strongest absorption peak (399 nm) is associated with the 7F0→5L6 electronic transition. The orange-red emission was observed at 588 nm (5D0→7F1), 612 nm (5D0→7F2), 648 (5D0→7F3), and 685(5D0→7F4) when excited at 399 nm. Measurements of the luminescence intensity ratio (R) between the 5D0→7F2 (electric dipole) transition and the 5D0→7F1 (magnetic dipole) transition predict that Eu3+ ions are situated at the symmetric sites in CaF2. The radiative parameters for the Eu: CaF2 crystal are calculated using the JOES code using the Judd-Ofelt theory. The calculated total radiative transition probability (AR) is 64.54 s−1, and the radiative lifetime (τR) is 15.57 ms. Radiative transition probabilities are 43.41,7.02 and 14.10, and branching ratios are 67.26 %,10.88 % and 21.85 % for 5D0→7F1, 5D0→7F25D0→7F4 transitions respectively.

Computational and optoelectronic investigations of red-emissive europium (III) β-diketonate with n-donor ligands for display applications

Europium complexes exhibiting red luminescence were prepared by employing β-diketone as main ligand and 1,10-phenanthroline as an additional ligand. Various methods, including 1H NMR, IR spectroscopy and analysis of optical band gap were employed to examine these complexes. The luminescent photophysical properties were investigated using PL spectroscopy and theoretical calculations were conducted to explore radiative transitions probabilities and Judd-Ofelt (J-O) parameters for transitions of type 5D0 → 7F2, 4. J-O parameters were determined using the JOES computer program and results were in good agreement with the outcomes obtained experimentally. The luminescence analysis results have verified the vibrant, single-color red emission of the prepared complexes. The band gap of ternary europium complexes, determined optically, electronically, and theoretically, falls within the range of 3–4 eV. This similarity indicates that these complexes are potentially suitable as semiconductor materials. The results from absorption, electrochemical and photophysical analyses indicate the potential use of synthesized complexes in lighting and display applications.

Static and dynamic strain-driven photoluminescence tuning in rare-earth doped perovskite oxide thin films

Recently, there have been significant interest in the wide potential of photoluminescence (PL) response of rare-earth doped perovskite oxide thin films in the field of optoelectronics. This work reports an effective method to modulate the PL properties of 0.8 mol%Sm3+-doped BaTiO3 (BTO:Sm) thin films through static and dynamic strain. BTO:Sm films were epitaxially grown on LaAlO3 (LAO), 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (PMN-PT), MgO, and Mica single-crystal substrates by pulsed laser deposition technique. Compared with the BTO:Sm/PMN-PT heterostructure which experiences minimal lattice mismatch effect, the PL intensity of BTO:Sm/LAO and BTO:Sm/MgO is enhanced by 818.1% and 1014.7%, respectively, due to static tensile/compressive strain (-0.429% and 0.461%) during the epitaxial growth process. In the flexible BTO:Sm/Mica heterostructure, dynamic strain is introduced through mechanical bending. Compared with the unbent state, the u-type and n-type bending modes increase the relative changes in PL intensity (ΔI/I) by 599.0% and 768.5%, respectively. Particularly, BTO:Sm/Mica also exhibits a remarkable optical transmittance exceeding 75% (500–2500 nm). The enhancement of PL intensity is closely related to the adjustment of lattice strain, which changes the crystal field strength of the BTO:Sm and the radiative transition probability. This work provides valuable insights for designing future optoelectronic devices and environmental monitoring equipment. It has the potential to advance photonics and sensor technologies, paving the way for innovation and exploration in these fields.

Instigating the Asymmetry of Dy3+ Ions Doped in Borate Glasses for Photonic Device w-LED Applications

For usage in solid state white light emitting device applications, dysprosium-activated calcium aluminum barium sodium borate glass was synthesized. The detailed understanding of physical, optical, structural, and photo-luminescence characteristics was examined and compared. To comprehend the oscillator strength of the ligands in the prepared glasses, the Judd-Ofelt intensity characteristics were assessed. The Ω2 greater relative oscillator strength value shows highest for the prepared glasses suggesting their cause due to hypersensitive transitions. In comparison to other glasses in the research, the potential radiative transition probabilities, branching ratios, and stimulated emission cross-section for 575 nm emission all exhibited higher values. The stimulated emission cross-section shows highest for 0.3 mol% Dy2O3 content in the present glasses. The asymmetry of synthesizedglass sample ratio has been evaluated and compared using Yellow to Blue (Y/B) emission ratio. Study of the emission spectra and assessment of CCT and DUV values for the glasses reveal emission in the CIE diagram's white light zone.

Structural, thermal and spectroscopic properties of Er2O3-doped oxyfluoro tellurophosphate glasses

Employing the melt quench method, the oxyfluoro tellurophosphate glasses (PTBMEr), doped with varying erbium concentrations, were prepared. Their physical, structural, optical, and luminescent characteristics were investigated using XRD, EDX, FTIR, absorption and Photoluminescence studies. The amorphous nature and elemental composition were identified using the XRD and EDX spectra. The J-O parameters and radiative parameters, including energy gap (ΔE), branching ratio (βR), radiative lifetime (τrad), and radiative transition probability (AR), were established for different excited levels of erbium in PTBMEr glass matrices. The visible emission spectra were acquired through excitation at a wavelength of 377 nm, resulting in a highly pronounced emission band at 544 nm, corresponding to the transition 4S3/2→ 4I15/2. The NIR emission spectra obtained through excitation at 980 nm showed a prominent broad emission band at 1534 nm pertaining to the transition 4I13/2→4I15/2. Within the set of prepared samples, the PTBMEr05 sample exhibits highest stimulated emission cross section of 0.75 × 10-20 cm2 for the transition 4S3/2→4I15/2. It also exbited superior parameters for the transition 4S3/2→4I15/2 including a stimulated emission crosssection of 1.19 × 10-20 cm2, gain bandwidth of 64.87 × 10-25 cm3, and optical gain of 53.41 × 10-24 cm2s. Experimental lifetime values for the excited level 4I13/2 of erbium in PTBMEr glasses were calculated and found to decrease with concentration due to non-radiative mechanisms and concentration quenching. These results reflect that PTBMEr05 glass is best suited for green laser emission devices and optical fiber communication windows.

Broadband near infrared emission of Er3+ ions doped fluorophosphate glasses for solid state laser applications

A series of glass compositions (P2O5 + Bi2O3 + Na2CO3 + SrF2 + xEr2O3) with different concentrations of erbium ions (Er3+) was synthesized using the melt quenching method and the samples were subjected to thorough characterization to explore their optical and structural properties. In order to ascertain the amorphous nature of the glass and acquire a deeper understanding of its chemical bonding, conventional methods of characterization, such as X-ray diffraction and Fourier transform infrared spectroscopy, were utilized. The Judd-Ofelt intensity parameters were computed using the absorption spectra of glasses doped with Er3+, providing vital information about the local environment and coordination of Er3+ ions in the glass matrix. Using the Judd-Ofelt intensity parameters and emission spectra to calculate the radiative parameters like total radiative transition probability (AT), radiative lifetime (τR) and radiative branching ratios for 4I13/2 → 4I15/2 transition. The McCumber theory is used to study absorption and emission cross-section for 4I13/2 → 4I15/2 transition. Prepared the PBNSEr05 glass sample suitable candidates for 1.53 μm solid state laser applications.

Temperature effect on spectral characters and dipole moment in short-lived excited singlet S1 state of 3HBI-7D-2HChromen-2-one laser dye in non-associative and highly viscous glycerol solvent

Steady state method is employed to study the effect of temperature on the absorption and emission characteristics of 3-(1H-benzo[d]imidazol-2-yl)-7-(diethylamino)-2H-chromen-2-one(3HBI-7D-2HChromen-2-one) laser dye in glycerol solvent. Temperature induces thermal effect on maxima absorption, emission wavelength, fluorescence intensity etc. Radiative and non-radiative transition probabilities mechanism, fluorescence lifetime, frequency assisted parameters decay rate constants, and activation energy is estimated. Advance thermochromic shift method is adopted to determine the ground and excited state dipole moments.

Line identification of extreme ultraviolet spectra from aluminum ions in EAST Tokamak plasmas

Extreme ultraviolet (EUV) spectra emitted from aluminum in the 5-340 Å wavelength range were observed in Experimental Advanced Superconducting Tokamak (EAST) discharges. Several spectral lines from aluminum ions with different degrees of ionization were successfully observed with sufficient spectral intensities and resolutions using three fast-time-response EUV spectrometers. The line identification uses three independent state-of-art computational codes for the atomic structure calculations, which provide the wavelengths and the collisional and radiative transition rate coefficients. These programs are hullac (Hebrew University—Lawrence Livermore Atomic Code), autostructure, and fac (Flexible Atomic Code). Using three different codes allows us to resolve some ambiguities in identifying certain spectral lines and assess the validity of the theoretical predictions.

Impact of ZnO on spectroscopic and luminescence characteristics of Sm2O3–SrO–B2O3 glasses for warm reddish orange light emitting applications

Sm2O3–SrO–B2O3 glasses containing ascending ratios of ZnO were created via the standard melt quenching approach. The optical and luminescent properties were assessed by analysing absorption, reflectance, excitation, and emission spectra obtained from measurements. The density, molar volume, metallization criterion, optical basicity, optical bandgap, Urbach energy, and dispersion parameters were evaluated and discussed. The spectral radiative transitions of the Sm3+ ion in different excited states were investigated using the Judd–Ofelt (J–O) theorem. The least square fit method was used to evaluate the J–O intensity parameters, which were subsequently utilized to determine radiative characteristics including transition probability, branching ratio, and lifetime. For all glasses, the reddish orange transition 4G5/2 → 6H7/2 demonstrated the highest strength and had the maximum values for stimulated emission cross section, radiative transition probability, and gain bandwidth. The chromaticity coordinates fell within the reddish orange region and the colour correlated temperatures ranged from 1840 to 1935 K, suggesting the suitability of the glasses for warm reddish orange emission-based laser and photonic applications.

Study of energy transfer process and radiative properties of CaAl4O7:Ho3+ phosphor for green light emission

This work comprehensively analyse the structural and photoluminescence properties of Ho3+-doped CaAl4O7 phosphor systems. X-ray diffraction (XRD), diffuse reflectance spectrum (DRS), photoluminescence (PL), and Fourier transform infrared (FT-IR) spectroscopy measurements were carried out, and Rietveld analysis confirmed the pure monoclinic structure of CaAl4O7:Ho3+ phosphor. The FT-IR spectrum showed absorption bands for the tetrahedral sites of the Al-O bonds and the octahedral sites of the Ca-O bonds, which indicate the formation of the CaAl4O7:Ho3+ phosphor. The diffuse reflectance spectrum shows sharp peaks in the visible and near-infrared regions. Photoluminescence excitation (PLE) measurements were performed on all the phosphor samples by monitoring emissions at 545 nm. Radiative properties such as total radiative transition probabilities (AT), radiative lifetime (τ rad), and branching ratios (β) are reported by Judd–Ofelt analysis and PLE spectral measurements. Upon 454 nm excitation, a green emission band is observed at around 545 nm (5F4 + 5S2 → 5I8), and these results indicate that x = 0.05 mol Ho3+ is the optimum concentration as the 5F4 + 5S2 → 5I8 emission intensity reaches its maximum. The emission intensity quenching and energy transfer mechanism are discussed, and the results suggest that the CaAl4O7:Ho3+ samples are suitable for green-emitting phosphor.

On the temperature dependence of transition intensities of rare-earth ions: A modified Judd-Ofelt theory

We report on a modification of the Judd-Ofelt theory accounting for thermal populations of Stark sub-levels of the multiplets involved in transitions in absorption and emission. The calculations require the data on the crystal-field splitting, the irreducible representations of Stark sub-levels and the selection rules for electric-dipole transitions. Simple formulas for absorption oscillator strengths and probabilities of radiative spontaneous transitions are obtained. The application of the proposed model allowed us to remove the contradiction between the transition intensities in absorption and emission (3H6 ↔ 3F4) for Tm3+-doped crystals. It was also used to explain the experimental temperature dependences of luminescence lifetimes of the 3F4 Tm3+ manifold in two widely used laser crystals, LiYF4 and Y3Al5O12. The case of Yb3+ ions featuring a small number of crystal-field sub-levels is also considered.

Simultaneously tuning the luminescent color and realizing an optical temperature sensor by negative thermal expansion in Sc2(WO4)3:Tb/Eu phosphors.

At present, many researchers are focusing on trivalent lanthanide (Ln3+)-doped thermally enhanced upconversion luminescent (UCL) materials with negative thermal expansion (NTE) properties. However, selective anti-thermal quenching downshifting emissions of the activator and thermal quenching of the sensitizer in a phosphor with NTE properties are not implemented. Herein, Tb3+/Eu3+ co-doped Sc2(WO4)3 phosphors synthesized by the solid-state method are explored in selectively enhanced red emission (Eu3+:5D0 → 7F2) due to the energy-transfer efficiency from Tb3+ to Eu3+ and the promoted radiative transition probability. The selective thermally quenched green emission (Tb3+:5D4 → 7F5) is owing to the change of energy transfer from Tb3+ to Eu3+ as the temperature increased. Moreover, under ultraviolet 365 nm excitation, the thermally stimulated color emission tuned from yellow to red with the increase in temperature. Based on the radically different thermal response downshifting the luminescence of the activator and sensitizer, the luminescence intensity ratio (LIR) of non-thermally coupled levels (NTCLs) for 5D0 (Eu3+) and 5D4 (Tb3+) is adopted for optical temperature sensing. The optimal relative sensitivity of temperature sensing in the Sc2(WO4)3:25%Tb3+/3%Eu3+ sample could reach 2.94% K-1 at 347 K. All these indicate that this Sc2(WO4)3:Tb3+/Eu3+ material is a promising candidate for high-sensitivity optical temperature sensing.

Structural, luminescent and in vitro studies of europium‐doped soda lime phosphate glasses

AbstractIn this article, we have reported the effect of varying concentration of europium (Eu) in (50 − x)% P2O5–25% Na2O–24% CaO–% Eu2O3, where x = 1, 3, 5. The glass samples were synthesised via conventional melt‐quench method. The impact of europium ion (Eu3+) on the structural, optical and luminescent properties of phosphate soda lime glasses has been studied using X‐ray diffraction (XRD), Fourier‐transformed infrared (FTIR) spectroscopy, ultraviolet‐visible spectroscopy, scanning electron microscopy coupled with energy‐dispersive spectroscopy and photoluminescent techniques. The amorphous nature of glass samples was confirmed by XRD patterns. FTIR confirmed the presence of various functional groups. The emission spectra of synthesised samples exhibited intense emission peaks corresponding to Eu3+ under excitation at 393 nm. Among all the peaks, the maximum intensity was observed for 5D0 → 7F2 transition. Judd–Ofelt (J–O) parameters (Ω2, Ω4) and other radiative parameters such as band width, radiative transition probabilities, stimulated emission cross‐sections and branching ratio were determined from emission spectra. The other photometric parameters such as CIE coordinates and colour purity were also determined. Furthermore, cytotoxic studies were carried out on normal cell line human embryonic kidney cells (HEK‐293) using MTT assay. Results showed that the prepared samples significantly enhanced growth in glass sample‐treated cells as compared to control cells. These findings suggest that synthesised glass samples are biocompatible in nature and have potential for applications in display devices and biomedical research area.

EFFECT OF PRASEODYMIUM ION CONCENTRATION ON OPTICAL AND LUMINESCENCE PROPERTIES OF TELLURITE GLASSES PRODUCED BY MELT-QUENCHING TECHNIQUE

Tellurite glasses with different concentration of praseodymium (Pr3+) ion was produced by melt-quenching technique. The effect of Pr3+ concentration on optical and luminescence properties was presented. The optical absorption spectra of Pr3+ ions in glasses were recorded in the UV-VIS-NIR region. By using the integrated absorption spectrum, the Judd-ofelt parameters for Pr3+ ions were derived. The Judd-Ofelt theory was used to calculate the radiative transition probability, stimulated emission cross-section, and branching ratio of the glasses. These findings support the use of these glasses in laser and other optical device applications.

Photoluminescence characteristics of Sm3+ activated Y2SiO5 orange emitting phosphors

The structural and photoluminescence characteristics of sol-gel-derived Y2SiO5 activated with triply ionized samarium ions were examined. Structural analysis was performed using XRD (X-ray diffraction) and FT-IR (Fourier Transform Infrared) spectral measurements. Lattice expansion was observed with an increased concentration of Sm3+ ions in the Y2SiO5 phosphor due to increased crystallite size. The observed spectra of diffuse reflectance and emission spectra of Y2SiO5 phosphors doped with Sm3+ ions were used for the analysis of optical and luminescence characteristics. J-O intensity parameters, Ω2 = 0.16 × 10−20 cm2, Ω4 = 0.16 × 10−20 cm2 and Ω6 = 0.16 × 10−20 cm2 were obtained for the Y2SiO5:0.03Sm3+ phosphor. Radiative transition probabilities (Arad), radiative lifetimes (τrad), and branching ratios (β) for a certain Sm3+ ion transition are presented. Photoluminescence spectra of Sm3+ activated Y2SiO5 phosphors show an orange emission under the n-UV excitation of phosphor. Dexter's theory on emission spectra supports the existence of dipole-dipole interactions between dopant ions. Furthermore, photometric and colorimetric studies were also accomplished to determine the emission behavior of the synthesized phosphors for their application in w-LEDs.

Impact of intensity error on temperature estimation in laser-induced breakdown spectroscopy: a numerical study

Laser-induced breakdown spectroscopy (LIBS) is a cutting-edge technique for the compositional analysis of multi-element materials. Under standard circumstances for laser-induced plasma (T e = 1 eV and N e = 1016 cm−3), we simulated the emission spectrum of a binary alloy (with 70 wt.% Cu–30 wt.% Al). We used the Saha ionization equilibrium formulas to calculate the population of neutral and ionized species of each constituent element, and the Boltzmann distribution to estimate the intensities of emission lines with radiative transition probabilities. The Stark broadening equation is then used to determine the line broadening, yielding a Lorentzian profile for each line. The sum of line emissions of all constituent species will approximate the alloy’s LIBS spectra in an assumption of ideal analytical plasma. Then, we generated random errors in the intensities of spectral lines ranging from 5% to 35%. To investigate temperature estimation accuracy, we utilized three well-established approaches: the Boltzmann plot (BP) method, the Saha–Boltzmann plot (SBP) method, and the Multi-elemental SBP (MESBP) method. As intensity error increases from 5% to 35%, the estimated temperature in the BP method deviates from 0.25% to 18.3%. Whereas the intensity error is almost unaffected using the SBP method and the MESBP method. The temperature deviation is less than 2% in both situations. This study is relevant to calibration-free LIBS, in which the exact temperature determination is crucial for the abundance estimation of trace, major, and minor elements.