Stark Splitting Research Articles

Spectroscopic properties and Stark splitting of Nd3+ ions in different host glasses to obtain pure blue laser

In this study, we investigated the spectroscopic properties and Stark splitting of Nd3+ in several typical host glasses by focusing on the 0.9 μm fluorescence (4F3/2 → 4I9/2). Absorption, emission spectra and decay curves of Nd3+ doped borate, phosphate, fluoride, tellurite, silicate, germanate and fluorophosphate glasses were measured. Judd−Ofelt parameters, Stark splitting and crystal field strength in these glasses were calculated and analyzed. Results demonstrated that broad absorption and emission bands, large Judd−Ofelt parameters (5.14 × 10−20 cm2), strong local field strength (7089.2 cm−1) and high values of fluorescence branching ratio (43.7%) and fluorescence lifetime (542.95 μs) of Nd3+ ions were found in silicate glass. Results indicate that silicate and germanate host glasses show promising potential for pure blue lasers by frequency doubling of 0.9 μm fluorescence.

Observation of Stark splitting in micro upconversion photoluminescence spectra of polycrystalline Ln3+ doped Y2O3 microspheres

In this study, Yb3+-Er3+-Tm3+ doped Y2O3 microspheres were synthesized using the solvothermal method. Structural, morphological, and elemental analysis was done using XRD, FESEM, and EDX characterization techniques. The optical properties of the samples were determined using UV–Vis-NIR spectroscopy and upconversion photoluminescence measurements. The anti-Stokes emission peaks from these polycrystalline phosphor microspheres were obtained using a commercial micro-photoluminescence setup equipped with a 976 nm laser as an excitation source at room temperature. It was compared with the emission spectra taken from a 2–3 mm spot size of 976 nm laser irradiation on the same sample. The micro-emission spectra were analyzed based on possible Stark splitting energy level transitions between the 2S+1LJ manifolds of Er3+ and Tm3+ ions. A detailed mechanism is outlined for emission in the entire visible region under 976 nm laser excitation.

Growth, structure, and polarized spectroscopy of monoclinic Er3+:MgWO4 crystal

We report on the growth, structure, and polarized spectroscopy of a novel promising laser crystal, erbium-doped magnesium monotungstate, Er3+:MgWO4. 1.01 t.% Er3+:MgWO4 was grown by the Top-Seeded Solution Growth method using Na2WO4 as a solvent. The crystal structure was refined by the Rietveld method. Er3+:MgWO4 belongs to the monoclinic class (sp. gr. P2/c, wolframite-type structure, lattice parameters: a = 4.6939(6) Å, b = 5.6747(4) Å, c = 4.9316(6) Å and β = 90.7858(4) Å. The transition intensities for Er3+ ions were determined using the Judd-Ofelt theory accounting for an intermediate configuration interaction (ICI). Er3+ ions in MgWO4 exhibit intense, strongly polarized and broad absorption and emission bands owing to their accommodation in distorted low-symmetry sites (C2). The stimulated-emission cross-section for the 4I13/2 → 4I15/2 transition is 0.31×10−20 cm2 at 1637 nm (light polarization: E || b ). The radiative lifetime of the 4I13/2 state is 4.85 ± 0.05 ms. The multiphonon non-radiative relaxation for Er3+ excited multiplets is quantified. Er3+ ions in MgWO4 feature large Stark splitting of the ground-state, ΔE(4I15/2) = 435 cm-1. Er3+:MgWO4 is attractive for low-threshold lasers at ∼1.64 µm.

Foundations, Market Failures and the Funding of New Music

In 1965, a short article entitled ‘On the Performing Arts: An Anatomy of their Economic Problems’ appeared in the American Economic Review, the flagship journal of the American Economic Association.1 Written by two Princeton-affiliated economists, William J. Baumol and William G. Bowen, the article laid out in eight short pages a powerful explanation for why the operating costs of so many performing arts organizations consistently overran their earnings, and why this tendency had become more pronounced over time. The problem was not that lavish budgets were being spent on productions, nor that musicians’ unions had wrung too many concessions from management. Rather, the problem was more prosaic, having to do with ‘differential rates of growth in the economy’.2 To illustrate the argument, Baumol and Bowen asked readers to perform a thought experiment: ‘Think of an economy divided into two sectors: one in which productivity is rising and another where productivity is stable.’3 For the sake of simplicity, they explicitly assumed a number of useful fictions: that labour can easily and frictionlessly move between the two sectors; that wage increases across the board will keep pace with productivity growth (a standard if problematic assumption in modern economic theory);4 and that the monetary supply is sufficiently controlled to maintain overall price stability. What, given these assumptions, is the outcome of such a stark split in the economy? In the productive sector, the increase in wages that workers receive will be offset by increased productivity. In the stagnant sector, wages will rise but output will not. And if an organization is to avoid bankruptcy, the only way to do so is by raising prices to cover the rise in labour costs. (Remember, one of Baumol and Bowen’s working assumptions is that wage increases will keep pace with productivity growth, in both productive and stagnant sectors.) Yet this solution to the problem creates another one, since over time prices in the unproductive sector will increase at a much faster rate than those in the productive one, making the products of the former unaffordable to an increasing number of workers.

Optical thermometry of Tm3+/Yb3+ Co-doped Ba3Gd2F12 up-conversion glass-ceramic with high sensitivity

In this work, Tm3+/Yb3+ co-doped Ba3Gd2F12 oxyfluoride glass-ceramic was synthesized by the conventional melt-quenching method, and an optical thermometer with high sensitivity was proposed accordingly. The structural and optical properties of Ba3Gd2F12: Tm3+/Yb3+ glass-ceramics were systematically investigated. After crystallization, the enrichment of Tm3+ ions in the Ba3Gd2F12 lattice leads to enhancing emission intensity, the prolonged lifetime of Tm3+ ions, and Stark splitting of emission spectra. The dependence of optical properties of Ba3Gd2F12: Tm3+ glass-ceramics on temperature were explored based on fluorescence intensity ratio of 3F2,3 ​→ ​3H6 and 1G4→3F4 transitions of Tm3+ ions. The maximum value of relative sensitivity SR reaches 1.02% K−1 at 457 ​K. This work indicates that the oxyfluoride glass-ceramic embedded with Ba3Gd2F12: Tm3+/Yb3+ nanoparticles is a candidate material with good performance for optical temperature sensors.

Stoichiometrically controlled synthesis and comparative study of photoluminescence of seven and eight coordinate complexes of Sm3+, Eu3+ and Tb3+ based on 6,6,7,7,8,8,8- heptafluoro-2,2-dimethyl-3,5-octanedione (Hfod) and imidazole

Taking the advantage of the unsaturation in the coordination of lanthanides, stoichiometrically controlled synthesis of seven– and eight–coordinate complexes of type [Ln(fod)3(im)] and [Ln(fod)3(im)2] was accomplished (Ln = La, Sm, Eu and Tb, fod is the anion of 6,6,7,7,8,8,8- heptafluoro-2,2-dimethyl-3,5-octanedione and im is imidazole). To study the effect of coordination geometry on the luminescence properties of a lanthanide ion, the steady state and time resolved spectra of the complexes are investigated in solutions, solid state and of doped PMMA thin hybrid films. A prominent distinction of the luminescent properties is observed between the two types of the complexes. The emission transitions of seven–coordinate complexes display extensive stark splitting compared to their eight–coordinate analogues. The seven–coordinate complexes (Eu = 985.18 μs and Tb = 402.88 μs) show longer lifetime of the excited states and higher intensity of hypersensitive transitions than their eight–coordinate analogues (Eu = 692.92 μs and Tb = 69.21 μs). It has been shown that the site symmetry could have profound effects on the luminescence properties (emission intensity, radiative lifetime, quantum yield and stark splitting of the emission transitions) of a lanthanide complex.

Synthesis, structure, phase controlled colour tuning of dinuclear Pr(III) and Tb(III) complexes with fluorinated β-diketone and heterocyclic Lewis base as UV light converters

Heteroleptic homo dinuclear complexes, [Pr(fod)3(μ-bpp)Pr(fod)3] and [Tb(fod)3(μ-bpp)Tb(fod)3] (fod is the anion of 6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedione (Hfod) and bpp is 2,3-bis(2-pyridyl)pyrazine) have been synthesized and thoroughly characterized. The 1H NMR spectra of the complexes are consistent with the dinuclear complex formation. In the absorption spectra, the 3P2 ← 3H4, 3P1 + 1I6 ← 3H4 and 1D2 ← 3H4 transitions of Pr(III) complex show considerable sensitivity towards the host medium and prominent stark splitting of these transitions is observed in chloroform and dichloromethane. The effect of phase change on photophysical properties of Pr(III) and Tb(III) complexes is investigated by observing the steady state and time resolved fluorescence spectra of the solid complexes, their solutions and PMMA doped thin hybrid films. Intense emission is observed for the PMMA doped hybrid materials of the complexes. In the case of [Pr(fod)3(μ-bpp)Pr(fod)3] complex doped PMMA, additional emission peaks are observed from the high energy excited states (3P2, 1I6, 3P1 and 3P0), indicating that the PMMA facilitates emission from the higher emitting levels. The emitting colour of Pr(III) complex shows phase dependence with the emission of blue and purple light in the solutions, orange in solid state and in the case of PMMA doped hybrid films at a doping concentration of 5 % and 10 %, the Commission Internationale de l'Eclairage (CIE) colour coordinates are in the white region x = 0.351, y = 0.377 and light blue region x = 0.313, y = 0.319, respectively. Intense green light emission is observed for the terbium complex in all media. The semiempirical theoretical tool of Sparkle/PM7 has been used for obtaining the geometry of the complexes.

Formula omitted]-odd Faraday rotation in intracavity absorption spectroscopy with particle beam as a possible way to improve the sensitivity of the search for the time reflection noninvariant effects in nature

Possible experiments on the observation of the P,T - odd Faraday effect (rotation of polarization plane for the light, propagating through a medium in the presence of an external electric field, P - is the space inversion, T - is the time reflection) caused by the electron electric dipole moment in atoms and molecules, are discussed theoretically. An observation is assumed to be performed on the basis of modern intra-cavity absorption spectroscopy (ICAS) combined with atomic (molecular) beam techniques. The P,T - odd optical rotation is due to the linear Stark splitting of atomic or molecular levels. This leads to the difference between the refractive indexes for the right and left circularly polarized photons.

Tracking Zone-wise perturbation during unfolding of some globular proteins using Eu(III) complex of Tetracycline as a probe exhibiting Stark splitting

Enhanced ‘Antenna effect’ of a suitably designed ternary complex of Eu(III), Tetracycline hydrochloride (TC) and globular proteins viz bovine serum albumin (BSA), human serum albumin (HSA) and β-lactoglobulin A (BLGA) in aqueous medium is employed to characterize the different partially unfolded states along with investigation of the micro- heterogeneous environment of the proteins during their stepwise unfolding. The zone-wise perturbation for the proteins upon denaturation by Urea and Guanidine hydrochloride (Gdn. HCl) is followed by the emission of Eu(III) through ‘Antenna Effect’ and that of the tryptophan (Trp) residues of the proteins as a function of denaturants both by steady state and time resolved emission study. With Gdn. HCl as denaturant, both BSA and BLGA show quenching of Eu(III) emission compared to pure protein while HSA exhibits an enhancement of antenna effect during unfolding as compared to that in its absence. In the presence of Urea, HSA and BSA show enhancement of antenna effect accompanied by Stark splitting of the 5D0→7F2 transition of Eu(III) although BLGA follows the similar pattern of quenching of Eu(III) emission as observed with Gdn. HCl without any Stark splitting. The proteins exhibit a two state transition with ΔGD values of ~ 2–3 kcal mol−1. Thus the use of Eu(III) emission as an efficient probe is advocating here to rationalize the microenvironment of the proteins during their stepwise unfolding.

Electric-field-dependent g factor for the ground state of lead monofluoride, PbF

The electric-field-dependent $g$ factor and the electron electric dipole moment (eEDM)-induced Stark splittings for the lowest rotational levels of $^{207,208}$PbF are calculated. Observed and calculated Zeeman shifts for $^{207}$PbF are found to be in very good agreement. It is shown that the $^{207}$PbF hyperfine sublevels provide a promising system for the eEDM search and related experiments.

Structure Determination of Europium Complexes in Solution Using Crystal-Field Splitting of the Narrow f-f Emission Lines.

Nine nona-coordinated Eu(III) complexes (1–9) studied here have three unsymmetric β-diketonate ligands and one chiral Ph-Pybox ligand, which can produce eight possible coordination isomers, depending on the position of the three unsymmetric β-diketonate ligands. Substituents on the β-diketonate ligands cause a rational structural rearrangement upon crystallization. Substituents with higher polarity, including −CN, −F, −Cl, −Br, −OMe, and −OEt, employ intercomplex hydrogen bonding to generate an association complex through structural rearrangement upon crystallization. Substituents with lower polarity, including −CF3, −SMe, and −Me, cause the most energetically favorable isomer to crystallize directly from solution. These two crystal structures exhibit well-resolved f–f emission lines with characteristic Stark splitting structures. This work revealed that the configuration of the Eu(III) complexes in solution can be determined by systematic comparison of their Stark splitting structures to those obtained from the solid phase using density functional theory (DFT)-based predictions combined with circular dichroism data.

Insight into the spectroscopic and thermometric properties of titanate phosphors via a novel co-excited laser system

An approach to enhance the photophysical properties of Er3+-Nd3+-Yb3+ codoped CaTiO3 perovskite phosphors synthesized via solid state reaction technique under 808 nm and 980 nm co-excitation has been described. The band gap analysis and Rietveld refinement has been done on the basis of UV–Vis and XRD spectra. Frequency upconversion observed in the developed phosphors has been explained with the help of steady rate equations. Fluorescence intensity ratio (FIR) based temperature sensing study of the developed phosphors for different combination of thermally coupled Stark levels under co-excitation has been analysed over a range of 303–573 K. Consequently, the maximum sensitivity ~10.9 × 10−3 K−1 at room temperature (303 K) with an excellent thermal resolution (~0.4 K) due to Stark splitting thermally coupled (2H11/2(1) &4S3/2(2)) levels in comparison to the conventional 2H11/2 &4S3/2 levels has been reported.

Estimation of sheath electric field in inductively coupled hydrogen plasma on the basis of Doppler-broadened absorption spectrum of hydrogen Balmer-α line

We examined the applicability of the Doppler-broadened absorption spectrum of the hydrogen Balmer-α line to the estimation of the sheath electric field in plasma. The Stark splitting of the fine-structure components was calculated by solving the time-independent Schrödinger equation at various electric field strengths, and the theoretical absorption spectrum was obtained by the superposition of the fine-structure components with the same Doppler broadening widths. The spectrum of the Balmer-α line of atomic hydrogen, which was measured by standard diode laser absorption spectroscopy, was fitted with the theoretical spectrum. We succeeded in determining the translational temperature of atomic hydrogen, which was obtained from the Doppler broadening width, and the electric field strength by the spectral fitting. We have evaluated that the minimum electric field strength that can be detected by the present method is approximately 350 V cm−1 when the translational temperature of atomic hydrogen is 400–500 K.

Effect of radiative energy transfer and direct excitation on the up-conversion and down-shifting emission properties of Er3+-doped Zn3(VO4)2

Er3+-doped Zn3(VO4)2 samples were synthetized by solid-state reaction process at 800 °C. The doping level was varied from 1.0 to 4.0 mol%. All samples were analyzed by different techniques such as X-ray diffraction, Raman spectroscopy, optical absorption and photoluminescent spectroscopy. X-ray diffraction patterns revealed a majority presence of Zn3(VO4)2, with residues of Zn2V2O7, Zn4V2O9, ZnO, and ErVO4. Raman spectroscopy displayed vibrational modes associated with the Zn3(VO4)2 compound. Additionally, vibrational modes with lower intensity related to Zn2V2O7 and ErVO4 compounds were also present, in concordance with X-ray diffraction patterns. UV–Vis optical absorption spectra showed four bands located at 2.23, 2.37, 2.53 and 2.74 eV which are due to the Er3+: 4S3/2, 2H11/2, 4F7/2 and 4F5/2 electronic transitions, respectively. The band gap energy (Eg) values were found around 2.75 eV. The visible down-shifting emission spectra of the Zn3(VO4)2 sample upon 350 nm excitation, revealed a broadband from 400 to 800 nm due to the VO43− tetrahedron. In presence of Er3+, the emission band exhibited sinks, which match well with absorption of the Er3+: 4F7/2, 2H11/2, 4S3/2 and 4F9/2 levels, indicating the existence of radiative energy transfer from the host to Er3+. This energy transfer gave rise to the NIR Er3+: 4I13/2 → 4I15/2 emission. Non-radiative energy transfer was ruled out by the no shortening of the decay time profiles. The up-conversion emission spectra recorded upon 980 nm diode laser excitation, showed the characteristics Er3+ emission bands in the green and red region, which linearly grow with the Er3+ content. Such process is dominated by an excited state absorption mechanism. The NIR down-shifting emission spectra upon 980 nm excitation, displayed the NIR Er3+ emission band attributed to the Er3+:4I13/2 → 4I15/2 transition. The Stark splitting exhibited by the NIR emission attained upon direct and indirect excitations, revealed the existence of two Er3+ sites, which are activated depending on the excitation mechanism.

Spectral broadening and ultrafast dynamics of a nitrogen-vacancy center ensemble in diamond

Many applications of nitrogen-vacancy (NV) centers in diamond crucially rely on a spectrally narrow and stable optical zero-phonon line transition. Though many impressive proof-of-principle experiments have been demonstrated, much work remains in engineering NV centers with spectral properties that are sufficiently robust for practical implementation. To elucidate the mechanisms underlying their interactions with the environment, we apply multi-dimensional coherent spectroscopy to an NV center ensemble in bulk diamond at cryogenic temperatures. Our spectra reveal thermal dephasing due to quasi-localized vibrational modes as well as ultrafast spectral diffusion on the picosecond timescale. The intrinsic, ensemble-averaged homogeneous linewidth is found to be in the tens of GHz range by extrapolating to zero temperature. We also observe a temperature-dependent Stark splitting of the excited state manifold, relevant to NV sensing protocols.

Laser Ablation in Liquid Synthesis and Optical Temperature Sensing of YGdO3:Er3+ Nanoparticles

YGdO3:Er3+ nanoparticles were successfully synthesized by pulsed laser ablation in liquid method. The structural and morphological properties of the product are investigated by X-Ray diffraction and transmission electron microscopy. The upconversion photoluminescence properties were investigated in detail. Obvious stark splitting phenomena were observed in the green and red emission bands. The decay behaviors of three emission bands were studied. Based on thermal coupled energy level related upconversion fluorescence intensity ratio, the temperature sensing properties of product were studied. Linear function has beenused to reveal the relationship between fluorescence intensity ratio and temperature. Using stark sublevels related emission bands, sensitivity of the temperature sensor was successfully enhanced. These results suggest the YGdO3:Er3+ nanoparticles prepared via pulsed laser ablation in liquid are promising luminescent materials for optical thermometry.

Optical nanomaterials with focus on rare earth doped oxide: A Review

Optical nanomaterials (ONMs) have attracted significant attention of the global research community owing to their several superior advantages. Some of the ONMs depict negligible photobleaching, bright emission, large electron-hole overlap integral, ease of coating on any surface, large Stoke/Antistoke shifts, higher photostabilites, easy to incorporate inside human body etc. These properties make them technologically highly efficient which helps in minimizing the global issue of energy crisis and improving the standard of living of common man. Several aspects of ONMs such as plasmonic nanomaterials, quantum dots, photonic crystals, and rare earth doped nanoparticles have been discussed. For covering various categories of luminescent nanomaterials (LNMs) based on composition, a brief introduction and importance of metal nanoclusters, carbon nano dots, organic-inorganic nanocomposites, and metal doped nanoparticles have been also included. This review article gives very concise overview of rare earth doped oxide nanoparticles covering several important aspects such as rare earth ion (RE) as dopant, oxide-based host, nanophosphors etc. The importance of LNMs, their advantages as well as drawbacks are also highlighted. Technologically important types of RE doped oxide nanoparticles pertaining to downconversion, upconversion, persistence and radioluminescence are also explained and covered in detail in this review article. Several recent applications involving LNMs in bioimaging, solar cell, thermal sensor, biosensor, anti-counterfeiting etc are explained. In the last section of the review, a comparison between nano and bulk rare earth doped oxide LNMs are discussed in terms of several photophysical properties such as dopant local symmetry, Stark splitting, emission intensity, luminescence lifetime, host to dopant energy transfer, quantum yield etc. Finally, this review article is concluded with summary, outlook, challenges, and future scope on the use of LNMs. Several important aspects of LNMs with focus on RE doped oxide nanoparticles have been covered in this review article which will help general readers in their further research, in this important area, for development of both fundamental sciences and applications involving LNMs.

Optical spectroscopy study of Eu-doped ions in BaAl2O4 phosphors

Computational and experimental methodology is employed to study optical properties in Eu-doped BaAl2O4 phosphors. The symmetry and detailed geometry of the Eu-dopant site, predicted by atomistic simulation, are used to calculate the crystal field parameters and the intensity parameters (Ω2 and Ω4) based on a Judd-Ofelt approach to the Eu3+ ion. The phenomenological intensity parameters are obtained from the emission spectra of the Eu-doped BaAl2O4 and compared to the theoretical results. Experimental and calculated values for the 7F1 energy sub-levels of the Eu3+ and maximum Stark splittings (ΔEmax) are also obtained.

Squeezed Coherent States in Double Optical Resonance

In this work, we consider a “Λ-type” three-level system where the first transition is driven by a radiation field initially prepared in a squeezed coherent state, while the second one by a weak probe field. If the squeezed field is sufficiently strong to cause Stark splitting of the states it connects, such a splitting can be monitored through the population of the probe state, a scheme also known as “double optical resonance”. Our results deviate from the well-studied case of coherent driving indicating that the splitting profile shows great sensitivity to the value of the squeezing parameter, as well as its phase difference from the complex displacement parameter. The theory is cast in terms of the resolvent operator where both the atom and the radiation field are treated quantum mechanically, while the effects of squeezing are obtained by appropriate averaging over the photon number distribution of the squeezed coherent state.

Solid solution of novel LixByGdEu (WO4)2 (B=Na, K) red phosphors: Influence of Na/K substitution on microstructures, Judd-Ofelt and luminescence properties for WLED applications

In the present investigation, new materials of the type LixByGdEu(WO4)2 (B= Na, K) have been synthesized by solid state reaction. The influence of Li/K and Li/Na ions on the photoluminescence properties and structures are presented in detail. Rietveld refinement indicates the crystalline phase of the compounds and incorporation of doping leads to change in the interatomic distance. The SEM observations shows that all the prepared phosphors have spheroid, bi-pyramidal shape with different grain size. An Optical energy bandgap of 3.0 and 3.2 eV were observed for LixByGdEu(WO4)2 (B= Na, K) phosphors. The Photoluminescence spectra shows that the phosphors can be excited by near UV light which is relevant for lighting technology. Luminescence emission spectrum reveals the two characteristic emissions located at 613 nm (electric dipole) and 586 nm (magnetic dipole). The 5D0→7F2 electric dipole transitions are dominant, indicating that Eu3+ ion occupies the single crystallographic site without the stark splitting in the host matrix. Interestingly, doping of Na, K shows 40% enhancement of photoluminescence intensity than reported LiGdEu(WO4)2 phosphor. The critical distance of energy transfer is found be 10 Å indicating the multipole-multipole interactions. Judd Ofelt (J-O) theory is implemented to explore the luminescence behavior and local structure around activator with respect to Eu3+ ion. The JO intensity parameter trend i.e, Ω2 > Ω4 indicate that the asymmetric environment around the activator. In addition, the Cathodoluminesence study also suggests the intense red emission of phosphors at low voltage and current. The chromaticity coordinates of the phosphors are much closer to NTSC trichromatic coordinates indicating the promising red phosphors with excellent luminescence properties. The CCT values around 3500K reveals that the LixByGdEu(WO4)2 (B= Na, K) red phosphors can be used for warm white LED applications.