Lifetimes Of Levels Research Articles

Influence of Bi+ ions on photoluminescence properties of Tm2O3 doped borotellurite glasses for the near-infrared emission applications

This paper reports the influence of bismuth ions (Bi+) on photoluminescence properties of Tm2O3 doped borotellurite based glasses (BTGS) with the composition (64-y)B2O3–30TeO2 – 5NaF- yBi2O3–1Tm2O3, where y = 0, 4, 8, 12 and 16 wt% for the near-infrared (NIR) emission applications. All glasses were prepared using the melt-quenching method and confirmed to exhibit amorphous nature by the X-ray diffraction (XRD) technique. The absorption spectra in the wavelength range of 300–2100 nm and emission spectra in the wavelength range of 400–2200 nm were studied. Increase of y wt. % value increases the 3H4→3F4 and 3F4→3H6 (near-infrared, NIR emission) intensities due to cross-relaxation (CR) and enhanced energy transfer processes between the active centres (Bi+ and Tm3+ ions), which are strongly influenced by bismuth content (Bi+) in the glass matrix. Based on Judd-Ofelt theory, the intensity parameters Ω2, Ω4 and Ω6 for each glass were determined and found to follow the trend Ω2>Ω4>Ω6 similar to the recently reported photonic glasses. Using the Ωλ parameters and reduced matrix elements, the calculation for the emission transition probability (A), radiative lifetime (τR), branching ratio (βR) and emission-cross sections (σPE) of 3H4, 3H5, and 3F4 energy levels were done and found to be slightly higher than fluoride and other oxide-based glasses because of the high density and refractive index values of the present samples.

Ferroelectric and Spectroscopic Properties of Ho3+/Yb3+ Co-Doped Pb(Mg1/3Nb2/3)O3-32PbTiO3 Crystal

In order to design a new multifunctional crystal with excellent ferroelectric and spectroscopic properties, experiments were carried out for Ho3+/Yb3+ co-doped Pb(Mg1/3Nb2/3)O3 -32PbTiO3 ferroelectric crystal using the flux method, the coercive field Ec of which is 11.86 kV/cm. Up-conversion luminescence emission bands, including an intense green emission band at 553 nm, a red band at 663 nm, and a weak infra-red band at 755 nm, are generated at 980 nm excitation. The main spectroscopic parameters, including radiative transition probability A(J′ − J), radiative lifetimes τrad, and branching ratios β, were predicted by applying Judd–Ofelt treatment. The obtained J-O intensity parameters are Ω2 = 0.531 × 10−20 cm2, Ω4 = 1.738 × 10−20 cm2, Ω6 = 0.530 × 10−20 cm2. The radiative lifetime of 5I7 level is 5.45 ms. The fluorescence lifetime of is 5F5 is 92.568 μs. The investigations show that Ho3+/Yb3+ co-doped Pb(Mg1/3Nb2/3)O3-0.32PbTiO3 crystal is a new type of multifunctional crystal integrating ferroelectric and spectroscopic properties, which has a potential application in the developing innovative multifunctional devices and lasers.

Correction to: Evaluation of background radiation level and excess lifetime cancer risk in Doon valley, Garhwal Himalaya

Correction to: Evaluation of background radiation level and excess lifetime cancer risk in Doon valley, Garhwal Himalaya

Tuning the Photoluminescence Properties of β‐NaYF4:Yb,Er by Bi3+ Doping Strategy

AbstractThe low luminous efficiency of upconversion materials limits their practical applications in various fields. The present study focuses on the efficient upconversion enhancement of β‐NaYF4:Yb,Er induced by Bi3+ doping. The XRD and SEM results show that introducing Bi3+ into the matrix lattice changes the microstructure and particle size of the crystal. The photoluminescence spectra show that at 6% Bi3+ doping, the red and green emission intensities are enhanced by 12 and 8 times, respectively. The reason could be the lattice distortion caused by Bi3+ doping, breaking the partial forbidden transition of rare‐earth ions. The fluorescence lifetime measurement reveals that the Bi3+ doping changes the environment around erbium ions, affecting the energy level lifetime of erbium ions, explaining the luminescence dynamics law. The present study provides a facile route to achieve nano/microstructures with intense upconversion luminescence with potential applications in optoelectronic devices.

Level Structure and Properties of Open f-Shell Elements

Open f-shell elements still constitute a great challenge for atomic theory owing to their (very) rich fine-structure and strong correlations among the valence-shell electrons. For these medium and heavy elements, many atomic properties are sensitive to the correlated motion of electrons and, hence, require large-scale computations in order to deal consistently with all relativistic, correlation and rearrangement contributions to the electron density. Often, different concepts and notations need to be combined for just classifying the low-lying level structure of these elements. With Jac, the Jena Atomic Calculator, we here provide a toolbox that helps to explore and deal with such elements with open d- and f-shell structures. Based on Dirac’s equation, Jac is suitable for almost all atoms and ions across the periodic table. As an example, we demonstrate how reasonably accurate computations can be performed for the low-lying level structure, transition probabilities and lifetimes for Th2+ ions with a 5f6d ground configuration. Other, and more complex, shell structures are supported as well, though often for a trade-off between the size and accuracy of the computations. Owing to its simple use, however, Jac supports both quick estimates and detailed case studies on open d- or f-shell elements.

Crystal growth, polarization spectral analysis derived from the broadband emission from the 1D2 level of Pr:GdScO3 crystal

Pr3+-doped GdScO3 single crystal was successfully grown by the Czochralski (Cz) method. Polarized absorption spectra, polarized fluorescence spectra, and fluorescence decay curves were measured at room temperature. The polarized spectroscopic property of Pr:GdScO3 crystal for new-wavelength transition in the near infrared (NIR) region was discussed for the first time. The absorption cross-sections at 600 nm were calculated to be 0.39×10−20 cm2 (E∥a), 0.32×10−20 cm2 (E∥b) and 0.4×10−20 cm2 (E∥c). The emission cross sections at 1053 nm of 1D2 energy level were calculated to be 0.86×10−20 cm2 (E∥a), 0.79×10−20 cm2 (E∥b) and 0.78×10−20 cm2 (E∥c), with FWHM of 57.54 nm, 57.96 nm and 58.96 nm, respectively. The fluorescence lifetime and radiative lifetime of the 1D2 energy levels of Pr3+ ions were 45.46 µs and 393.94 µs, respectively. Those results show that the Pr:GdScO3 crystal should be the potential near infrared laser gain medium originated from the 1D2 transition.

Imaging photodissociation dynamics of MgO at 193 nm

In this work, we used time-sliced ion velocity imaging to study the photodissociation dynamics of MgO at 193 nm. Three dissociation pathways are found through the speed and angular distributions of magnesium. One pathway is the one-photon excitation of MgO(X1Σ+) to MgO(G1Π) followed by spin-orbit coupling between the G1Π, 33Π and 15Π states, and finally dissociated to the Mg(3Pu)+O(3Pg) along the 15Π surface. The other two pathways are one-photon absorption of MgO(A1Π) state to MgO(G1Π) and MgO(41Π) state to dissociate into Mg(3Pu)+O(3Pg) and Mg(1Sg)+O(1Sg), respectively. The anisotropy parameters of the dissociation pathways are related to the lifetime of the vibrational energy levels and the coupling of rotational and vibronic spin-orbit states. The total kinetic energy analysis gives D0(Mg−O)=21645±50 cm−1.

Lifetimes and intensities study for the γ and β systems of CN radicals extending to very high vibrational state

The γ (A2Π-X2Σ+) and β (B2Σ+-X2Σ+) systems of cyano (CN) radicals were studied using the highly correlated ab initio approach. The complex behavior of the excited-state wave function calculated at the complete active space self-consistent field (CASSCF) and multireference configuration interaction (MRCI) levels has a great influence on the quality of the transition dipole moment curves (TDMCs). Combining the TDMCs and the Rydberg–Klein–Rees (RKR) potential curves at the MRCI + Q/aV5Z-DK level, the spectroscopic parameters of the higher vibrational bands for the γ (v′ = 0–50 ← v″ = 0–53) and β (v′ = 0–33 ← v″ = 0–53) systems were investigated. The radiation lifetimes of the vibrational levels (v′ = 0–15) were obtained. A list of wavelengths and Einstein A coefficients of the lower vibrational bands (v′ = 0–2 ← v'' = 0–2) is provided and compared with other results. The spectral intensities of the γ system 2–0 band and the β system 0–0 band at different temperatures (300, 5000, and 10,000 K) are discussed. As the temperature increases, the bandwidths become broader, and the intensities decrease. These results are relevant for the applications in astrophysics and chemistry, especially in space vehicles.

Theoretical Study of the Rotational Structure of the c4′1Σu + (6)–X1Σg +(0–9) Absorption Bands of N2

Abstract We have theoretically determined the absorption oscillator strengths and wavenumbers for rotationally resolved transitions of the c4′1Σu + (6)-X1Σg +(0–9) bands of N2, which are relevant to analyze the spectra of planetary atmospheres. The Molecular Quantum Defect Orbital method has been used in our calculations. The interaction between the c4′1Σu + (6) Rydberg state and the b′1Σu + valence states has been considered using an adequate rovibronic energy matrix. In addition, we have calculated the lifetimes of the rotational levels of the c4′1Σu + (6) state. We hope that the reported data, most of them for the first time, can be useful in the interpretation of planetary atmospheres where N2 is present.

Site-Selective Eu3+ Luminescence in the Monoclinic Phase of YSiO2N

Eu3+-doped YSiO2N phosphor was synthesized, and its crystal structure was analyzed by single-crystal X-ray and neutron powder diffraction techniques. The new crystal structure of YSiO2N with the monoclinic lattice (space group C2/c) composed of nonequivalent [YO6N2] dodecahedra was identified, and, in this structure, five different Y3+ sites take Ci or Cn symmetry. Based on the experimentally determined crystal structure, we characterized the luminescence properties of the Eu3+ ions with site-selective and time-resolved spectroscopy. The Eu3+ ions at the Y: Cn sites show intense 5D0 → 7F2 electric dipole luminescence peaking at 626 nm with a short lifetime (0.61 ms) due to the lack of inversion center. In the centrosymmetric Ci sites, the lifetime of the 5D0 level was quite long (5.51 ms), and the strongest three peaks are assigned to the 5D0 → 7F1 magnetic dipole transition instead of 5D0 → 7F2. The anomalous temperature dependence of the long lifetime for Eu3+: 5D0 at this Ci site at low temperatures suggests that the slow radiative rate can be influenced by the thermal distortion of centrosymmetry. The thermal quenching mechanism of the Eu3+: 5D0 luminescence at both sites is considered to be due to the charge transfer states related to the N3– ions in the [Eu3+O6N2] dodecahedra rather than the multiphonon relaxation mechanism. This study shows the potentials of Eu3+ luminescence in oxynitride coordination and provides new insights into the material design guidelines for near-UV excitable red phosphor activated with Eu3+ ions.

Semi-empirical determination of radiative parameters for metastable Sc II levels

We present a semi-empirical parametrization method for calculation of spontaneous radiative decay rates of forbidden transitions on an example of analysis of experimental data for Sc II. The values of transition probabilities and radiative lifetimes of metastable levels are in perfect agreement with experimental ones. The obtained results are compared with other calculated data available. The predicted values of radiative parameters for all Sc II metastable levels are presented.

Synthesis and enhanced photoluminescence properties of red emitting divalent ion (Ca2+) doped Eu:Y2O3 nanophosphors for optoelectronic applications

This work presents the synthesis of Y2O3:Eu3+,xCa2+ (x = 0 mol%, 1 mol%, 3 mol%, 5 mol%, 7 mol%, 9 mol%, 11 mol%) nanophosphors with enhanced photoluminescence properties through a facile solution combustion method for optoelectronic, display, and lighting applications. The X-ray diffraction (XRD) patterns of the proposed nanophosphor reveal its structural properties and crystalline nature. The transmission electron microscope (TEM) results confirm the change in the shape of the particle and aggregation of particles after co-doping with Ca2+. Fourier transform infrared spectroscopy (FTIR) and Raman vibrations also confirm the presence of Y–O vibration and subsequently explain the crystalline nature, structural properties, and purity of the samples. All the synthesized nanophosphors samples emit intense red emission at 613 nm (5D0→7F2) under excitation with 235, 394 and 466 nm wavelengths of Eu3+ ions. The photoluminescence (PL) emission spectra excited with 235 nm illustrate the highest emission peak with two other emission peaks excited with 466 and 394 nm that is 1.4 times higher than 466 nm and 1.9 times enhanced by 394 nm wavelength, respectively. The emission intensity of Y2O3:Eu3+,xCa2+ (5 mol%) is increased 8-fold as compared to Eu:Y2O3. Doping with Ca2+ ions enhances the emission intensity of Eu:Y2O3 nanophosphors due to an increase in energy transfer in Ca2+→Eu3+ through asymmetry in the crystal field and by introduction of radiative defect centers through oxygen vacancies in the yttria matrix. It is also observed that the optical band gap and the lifetime of the 5D0 level of Eu3+ ions in Y2O3:Eu3+,xCa2+ nanophosphor sample gets changed with a doping concentration of Ca2+ ions. Nanophosphor also reveals high thermal stability and quantum yield as estimating activation energy of 0.25 eV and 81%, respectively. CIE, CCT, and color purity values (>98%) show an improved red-emitting nanophosphor in the warm region of light, which makes this material superior with a specific potential application for UV-based white LEDs with security ink, display devices, and various other optoelectronics devices.

Theoretical study on the transition properties of AlF

Potential energy curves of the X1Σ+ and A1Π states of the AlF molecule are studied through the combination of the multi-reference configuration interaction (MRCI) approach and Davidson corrections (MRCI+Q). The AWCV5Z basis set is employed in the calculations. The transition dipole moments (TDMs) of the A1Π ↔ X1Σ+ transition are explored based on the AWCV5Z basis set and (4, 2, 2, 0) active space. The Schrödinger equation is solved via the LEVEL 8.2 program, and the vibrational levels and rotational constants of the X1Σ+ and A1Π states are calculated. It is shown that the AlF molecule has high diagonal Franck–Condon factors (f 00 = 0.9949 and f 11 = 0.9854) and large Einstein coefficients for the transition of A1Π (ν′ = 0) ↔ X1Σ+ (ν″ = 0). In addition, the radiative lifetimes of the vibrational levels are close to 10−9 s for the A1Π state. The line intensities of the A1Σ (ν′ = 4 – 15) ↔ X1Σ+ (ν″ = 0) transitions are also calculated. The calculated TDMs and transition probabilities in this work are credible and provide some guidance for the study of similar transitions, particularly for exploring interstellar space.

Evaluation of background radiation level and excess lifetime cancer risk in Doon valley, Garhwal Himalaya

AbstractRadionuclides such as Ra-226, Th-232 & K-40 occurs naturally in the earth crust from its creation and are main contributor to the dose received by human beings. The present study was carried-out in the Doon valley which is outlined in the Main Boundary Thrust (MBT) region of Garhwal Himalaya in Uttarakhand, India. The collected soil/rock samples were analyzed by NaI(Tl) Gamma ray spectrometry for the analysis of radionuclides and hence measuring the various health hazard indices and Excess lifetime cancer risk. Radionuclide (226Ra, 232Th & 40K) content were found to vary from 47 ± 9 to 442 ± 50 Bq Kg−1, 45 ± 17 to 101 ± 16 Bq Kg−1 & 320 ± 281 to 947 ± 197 Bq Kg−1 respectively and were higher than the world average values which are 35 Bq Kg−1, 30 Bq Kg−1 and 400 Bq Kg−1 respectively. Higher radionuclide content contributes to higher amount of absorbed doses which was found to vary from 93 to 259.6 ηGyh−1 with a mean value of 112.5 ηGyh−1 and Gamma index which found to vary from 0.73 to 1.92 with a mean value of 0.96. Lastly, on the basis of annual effective doses received to humanoid, Excess lifetime cancer risk was measured which varies from 0.48 × 10–3 to 1.34 × 10–3 with an average value of 0.65 × 10–3 and was much below the world’s average value of 1.45 × 10–3.

Influence of Sm3+ ion concentration on the photoluminescence behavior of antimony lead oxy fluoro borate glasses

The synthesis and characterization of a new glass series with the chemical composition 70B2O3–20PbO-5Sb2O3–(5-X) NaF-XSm2O3 where X is 0.1, 0.5, 1.0, 1.5, 2.0 and 2.5 were discussed in detailed in this paper. The glasses were made by using the traditional melt quenching process, and their spectroscopic behavior was studied to understand their utility in the development of lasers, light-emitting diodes (LEDs) and optical devices. Fourier-Transform Infrared (FT-IR) spectroscopy and EDX studies have been conducted to identify the functional groups and elemental composition present in the as prepared undoped glass. Optical and luminescent behaviors of the as prepared glasses were studies using absorption, photoluminescence (PL) excitation, PL emission and PL decay spectral features. The strengths of absorption bands called oscillator strength were calculated by using absorption spectral data and subsequently subjected to Judd-Ofelt (J-O) analysis to estimation various radiative properties like radiative transition probability (AR), total radiative transition probabilities (AT), branching Ratios (βR) and the radiative lifetimes (τR) for the prominent fluorescent levels of the Sm3+ ions in the titled glasses. The experimental lifetimes (τexp) measured from the PL decay curves are correlated with τR to estimate quantum efficiency (ƞ) of the as prepared glasses. The quantum efficiency, emission cross sections and other radiative parameters along with the CIE coordinates estimated for the Sm3+ ions doped titled glasses finally allows us to contemplate its potentiality for the fabrication of optoelectronic devices in visible reddish-orange region.

Metastable states of Si− observed in a cryogenic storage ring

We have used the Cryogenic Storage Ring (CSR) at the Max Planck Institute for Nuclear Physics to study long-lived metastable states of the silicon anion. A ${\mathrm{Si}}^{\ensuremath{-}}$ beam of 58 keV kinetic energy was stored in the ultrahigh cryogenic vacuum of the CSR, employing only electrostatic deflection elements. We used laser systems at various wavelengths to infer information on the decay of the metastable anionic states by selective photodetachment. Our results give evidence of an excited anionic state for which we determine the extremely long lower lifetime limit of 5.7 h at 90% confidence level, consistent with theoretical predictions for the $^{2}D$ term. Furthermore, we find an average lifetime of $\ensuremath{\tau}=(22.2\ifmmode\pm\else\textpm\fi{}2.5)$ s for the weakly bound $^{2}P$ states, employing coincidence counting with a pulsed nanosecond laser at 2.45 $\ensuremath{\mu}\mathrm{m}$. Using a laser depletion technique, we produce a pure ground term $^{4}S_{3/2}\phantom{\rule{4pt}{0ex}}{\mathrm{Si}}^{\ensuremath{-}}$ beam, and we quantify the fraction of ions in metastable states in our initial ion sample. We combine our experimental efforts with state-of-the-art multiconfiguration Dirac-Hartree-Fock calculations for the radiative lifetimes of all metastable levels of ${\mathrm{Si}}^{\ensuremath{-}}$. We find these calculations to be in excellent agreement with our measurements and to improve previous efforts considerably.

Experimental evidence of exact E(5) symmetry in Kr82

The low-lying positive-parity structures of $^{82}\mathrm{Kr}$ have been investigated following their population in the $^{76}\mathrm{Ge}(^{9}\mathrm{Be},3n)$ reaction at ${\mathrm{E}}_{\mathrm{lab}}\ensuremath{\approx}31\phantom{\rule{0.28em}{0ex}}\mathrm{MeV}$ and using a large array of Compton suppressed HPGe clovers as the detection setup. Apart from other spectroscopic measurements, level lifetimes of the states have been extracted using the Doppler shift attenuation method. The level energies and the associated transition probabilities exhibit superlative overlap with the calculations in the framework of the interaction boson approximation and the E(5) model. The $^{82}\mathrm{Kr}$ nucleus, thus, exemplifies the critical point of phase (shape) transition from the U(5) (spherical vibrator) to the O(6) ($\ensuremath{\gamma}$-soft rotor) paradigms of nuclear structure.

Quenching effect of upper laser level lifetime of Fe2+ ions in ZnSe by free electrons

We theoretically and experimentally examined the assumption that the lifetime excited state of Fe2+ in ZnSe:Fe crystal is quenched by free electrons. The effect of the electron beam current value on the temporal characteristics of the luminescence was studied. Three variants, including a sample in the electronic circuit in the case of Fe2+ ions luminescence excitation in a ZnSe:Fe crystal by a beam of accelerated electrons, were first considered theoretically. These variants differ in external electric field magnitude in the sample, which affects the concentration of free electrons in the excited region of the sample. Equations describing the time dependence of the sample's electron density were derived. The luminescence decay kinetics of Fe2+ ions in ZnSe:Fe crystal excited by electron pulse with different electron beam current values and short-pulse optical radiation were obtained. The values of the quantities that determine the temporal characteristics of the luminescence decay depending on the electron beam current were found.

The micro-pulling-down growth of Tm:LuAG and Tm,Pr:LuAG crystals and optical properties

Tm 3+ doped and Tm 3+ , Pr 3+ co-doped Lu 3 Al 5 O 12 (LuAG) garnet single crystals have been successfully grown by the micro-pulling-down (μ-PD) method. The absorption spectra, fluorescence spectra and lifetimes were investigated at room temperature. In the absorption spectra, the transition centered at 782 nm matches well with the GaAlAs LDs laser pumping. The incorporation of Pr 3+ into Tm 3+ -doped LuAG crystals enhanced the intensity of 1.5 μm emission and decreased the fluorescence lifetime of the lower energy level for 1.5 μm emission from 10.427 ms to 2.603 ms. The results indicate that Tm,Pr:LuAG crystal can be promising candidate for near infrared 1.5 μm laser materials. • Tm:LuAG and Tm,Pr:LuAG crystals have been successfully grown by the micro-pulling-down (μ-PD) method. • Spectral parameters of Tm:LuAG and Tm,Pr:LuAG crystals were obtained and compared. • The fluorescence mechanism of Tm,Pr:LuAG crystal has been studied for the first time.

Enhanced and modulated visible luminescence of Pr3+:CaF2 crystal by co-doping R3+ (R=Y, Gd, Lu) ions

A series of 0.6 at% Pr:CaF2-RF3 (R = Y3+, Gd3+, Lu3+) crystals have been successfully grown by the temperature gradient technique(TGT). The absorption spectra, fluorescence spectra, and fluorescence decay curves were measured and analyzed at room temperature. When the R3+ concentration is higher than a certain value, the diffraction peaks of Pr:CaF2-RF3 crystals were well indexed to the (Ca,Y)F2 phase. By co-doping R3+ ion (R=Y3+, Gd3+, Lu3+), the spectral performance of the crystals could be significantly improved and the function effect is also different. For 0.6 at% Pr, 28.5 at% Y:CaF2 crystal, the fluorescence lifetime of 3P0 energy level was fitted to be 45.46 µs, and the emission cross sections of 3P0→3H6 (605 nm), and 3P0→3F2 (641 nm) were calculated to be 1.78 × 10−20 cm2, and 4.61 × 10−20 cm2 with the full width at half (FWHM) of 20.1 nm and 6.8 nm, respectively. The 0.6 at% Pr, 28.5 at% Y:CaF2 crystal could be favorble laser medium for ultra-fast laser opreration at 605 nm and 641 nm. For 0.6 at% Pr, 18 at% Gd:CaF2 and 0.6 at% Pr, 10 at% Lu:CaF2 crystals, the spectral quality factors σem•τf of 3P0→3F2 transition (642 nm) were calculated to be 614.18 × 10−20 cm2•µs and 506.36 × 10−20 cm2•µs with the FWHM of 3.7 nm and 5.3 nm. All the results show that 0.6 at% Pr, 18 at% Gd:CaF2 and 0.6 at% Pr, 10 at% Lu:CaF2 crystals are promising gain media for high-efficiency visible laser output at 642 nm, which would compete with commercial Pr: YLF crystal in the future.