Excitation Spectra Research Articles

Surface excitation of Rydberg dressed quantum droplet of Bose–Einstein Condensates

We have considered a quantum droplet of two components of Bose–Einstein condensate (BEC) inside the electron of a Rydberg atom to study the surface mode of collective excitation using the Bogoliubov theory of excitation. We have calculated the surface excitation spectrum for various Rydberg electron-atom interaction strengths. From the energy spectrum, we calculated the surface tension of the droplet as a function of Rydberg electron-atom interaction strength. Our study shows that the electron-atom interaction enhances the surface energy; hence, the droplet will be more stable inside the electron of a Rydberg atom.

Unraveling the photophysical response of BaLaLiTeO6:Dy3+ double perovskites with excellent thermal stability for colour tunable LEDs and optical thermometry

The quest for reliable phosphors has accelerated amidst a growing demand for cost-effective, high-performance multifunctional phosphors. Incorporating thermometric application into double perovskite phosphors can enhance their multifaceted features for diverse applications. The present work endeavours to develop a series of BaLaLiTeO6:Dy3+ double perovskites via a solid-state reaction route, stressing their application in next-generation colour-tunable LEDs and non-contact luminescence thermometry. X-ray diffraction, Raman and FTIR spectroscopy analysis were done to make inferences about the structural modifications induced by the substitution of Dy3+ at the La3+ site of BaLaLiTeO6. An extensive investigation of optical characteristics was carried out by diffuse reflectance spectroscopy, photoluminescence spectroscopy and decay curve analysis. Prominent photometric parameters were also evaluated to assess the commercial feasibility of the developed phosphors in photonic applications. Judd-Ofelt parameters were estimated from the photoluminescence excitation spectra of BaLaLiTeO6:Dy3+ for the first time. Furthermore, the values of radiative parameters, fluorescence decay time and quantum efficiency suggested the suitability of the developed phosphor as a competent material. A comprehensive analysis of BaLaLiTeO6:Dy3+ as a thermographic phosphor was done by temperature-dependent photoluminescence spectroscopy. The potential use of this material in luminescence temperature sensing was probed by estimating the thermometric figures of merit based on the fluorescence intensity ratio (FIR). An absolute sensitivity of 22.17 × 10−4 K−1 was achieved at a temperature of 500 K and a remarkable maximum relative sensitivity of 2.34 %K−1 was attained at 250 K, which is much higher than other Dy3+ substituted thermographic phosphors. All these culminated features of BaLaLiTeO6:Dy3+ phosphor proved their prospective applications in thermally stable colour-tunable LEDs, wLEDs and as non-contact optical temperature sensors.

Exploration of Volatileomics and Optical Properties of Fusarium graminearum-Contaminated Maize: An Application Basis for Low-Cost and Non-Destructive Detection.

Fusarium graminearum (F. graminearum) in maize poses a threat to grain security. Current non-destructive detection methods face limited practical applications in grain quality detection. This study aims to understand the optical properties and volatileomics of F. graminearum-contaminated maize. Specifically, the transmission and reflection spectra (wavelength range of 200-1100 nm) were used to explore the optical properties of F. graminearum-contaminated maize. Volatile organic compounds (VOCs) of F. graminearum-contaminated maize were determined by headspace solid phase micro-extraction with gas chromatography-tandem mass spectrometry. The VOCs of normal maize were mainly alcohols and ketones, while the VOCs of severely contaminated maize became organic acids and alcohols. The ultraviolet excitation spectrum of maize showed a peak redshift as fungi grew, and the intensity decreased in the 400-600 nm band. Peak redshift and intensity changes were observed in the visible/near-infrared reflectance and transmission spectra of F. graminearum-contaminated maize. Remarkably, optical imaging platforms based on optical properties were developed to ensure high-throughput detection for single-kernel maize. The developed imaging platform could achieve more than 80% classification accuracy, whereas asymmetric polarization imaging achieved more than 93% prediction accuracy. Overall, these results can provide theoretical support for the cost-effective preparation of low-cost gas sensors and high-prediction sorting equipment for maize quality detection.

Structural and luminescence properties of Y2O3:Ho3+ phosphor: Potential applications in plant cultivation LEDs and thermoluminescent dosimetry

Current research on Y2O3:Ho3+ phosphors highlight their promising luminescence properties, but often lacks an environmentally friendly synthesis method and comprehensive analysis of their applications. In this study, we address these gaps by successfully synthesizing Y2O3:Ho3+ phosphors using a green synthesis route with varying concentrations of Ho3+. Our work provides detailed characterization of their photoluminescence (PL) and thermoluminescent (TL) properties. The PL excitation (PLE) spectra reveal a distinct peak at 439 nm, attributed to the 5I8→(5K5; 5G5) transition of Ho3+ions. Upon excitation at 439 nm, the emission spectra show a sharp emission peak around 660 nm from the 5F5→5I8 transition, with the 0.1 mol% Ho3+ phosphors exhibiting particularly strong red emission, indicating their suitability for indoor plant cultivation under LED lighting. Additionally, TL properties were evaluated after gamma-ray exposure, with the highest emission intensity at 0.1 mol% Ho3+ concentration. TL glow curves were analyzed for various radiation doses using the Computerized Glow Curve Deconvolution (CGCD) method, and TL trapping parameters were determined through Chen's peak shape and the Initial Rise methods. This work demonstrates significant potential for using these phosphors to enhance indoor plant growth and for applications in thermoluminescent dosimetry (TLD).

Active fluctuations in the harmonic chain: phonons, entropons and velocity correlations

Non-equilibrium random fluctuations of a non-thermal nature are a defining feature of active matter. In this work, we study the collective excitations of active systems at high density, focusing on a one-dimensional chain of elastically coupled inertial particles, where activity is modeled by an Ornstein–Uhlenbeck process. The excitation spectrum reveals two types of fluctuations: thermally excited phonons, analogous to those in passive crystals, and entropons, which are associated with entropy production due to active forces. These fluctuations exhibit distinct properties: only entropons generate spatial velocity correlations and violate the standard fluctuation-response relation. We derive exact expressions for equal-time velocity and displacement correlations, as well as for the structure factor, identifying the contributions from both phonons and entropons. Finally, we explore the dynamical properties of these excitations through steady-state two-time correlations, such as the intermediate scattering function and mean-square displacement. Both phonon and entropon fluctuations are characterized by a long-wavelength overdamped regime and a short-wavelength underdamped regime. In the large persistence case, entropons decay more slowly than phonons, and activity generally suppresses the oscillations typical of the underdamped regime.

Tunable Spectral Emission from 0D Rb3ZnBr5 Crystals for Single‐Component Multi‐Color LED Applications

AbstractThe development of efficient, stable, and cost‐effective luminescent materials is crucial for advancing lighting and display technologies. In this study, a series of tunable luminescent materials based on the novel 0D all‐inorganic perovskite (AIP) crystal Rb₃ZnBr₅ (RZB) is obtained. The emission of Sn2⁺ doped RZB spans the entire visible light range and extends into the near‐infrared (NIR) region, achieving a photoluminescence quantum yield (PLQY) of 75%. The distinct lifetimes combined with theoretical calculations, indicate that the broadband dual‐peak emissions at 496 and 636 nm originate from the singlet and triplet states of Sn2⁺, respectively, which is rarely observed in Sn2⁺‐doped perovskite crystals. The phosphor RZB:Sn2⁺ demonstrates the high thermal stability, along with excellent moisture and air stability. Co‐doping RZB with Sn2⁺ and Mn2⁺ broadens the excitation spectrum and allows precise control over the excitation wavelength, facilitating dynamic transitions from warm white to yellow and green light. This feature is particularly beneficial for multicolor LEDs and multi‐level anti‐counterfeiting applications.

Comparison of PMMA layers doped with methyl red and CdSe quantum dots for application in fibre optic

The paper presents a study of the luminescence properties in the visible spectral range of poly(methyl methacrylate) (PMMA) doped with organic dye-methyl red and CdSe quantum dots. The emission spectra of polymer-doped composite structures were investigated and compared with pure PMMA. Optical characterisation was carried out, focused on the measurement and analysis of excitation and luminescence spectra. Comparison of the spectroscopic characteristics of the developed materials allowed comparing the effect of doping on the luminescence properties of the obtained materials and considering their potential application as luminescent materials in fibre optic sensors.

Tuning the Spin Interaction in Nonplanar Organic Diradicals through Mechanical Manipulation.

Open-shell polycyclic aromatic hydrocarbons (PAHs) represent promising building blocks for carbon-based functional magnetic materials. Their magnetic properties stem from the presence of unpaired electrons localized in radical states of π character. Consequently, these materials are inclined to exhibit spin delocalization, form extended collective states, and respond to the flexibility of the molecular backbones. However, they are also highly reactive, requiring structural strategies to protect the radical states from reacting with the environment. Here, we demonstrate that the open-shell ground state of the diradical 2-OS survives on a Au(111) substrate as a global singlet formed by two unpaired electrons with antiparallel spins coupled through a conformational-dependent interaction. The 2-OS molecule is a "protected" derivative of the Chichibabin's diradical, featuring a nonplanar geometry that destabilizes the closed-shell quinoidal structure. Using scanning tunneling microscopy (STM), we localized the two interacting spins at the molecular edges, and detected an excited triplet state a few millielectronvolts above the singlet ground state. Mean-field Hubbard simulations reveal that the exchange coupling between the two spins strongly depends on the torsional angles between the different molecular moieties, suggesting the possibility of influencing the molecule's magnetic state through structural changes. This was demonstrated here using the STM tip to manipulate the molecular conformation, while simultaneously detecting changes in the spin excitation spectrum. Our work suggests the potential of these PAHs as all-carbon spin-crossover materials.

Tunable broadband luminescence of the novel Sn2+ doped oxyfluoride glass and glass-ceramics for W-LEDs

The demand for white-light luminescent materials for the white-light-emitting diodes (W-LEDs) field has been growing in modern life. In this work, a series of Sn2+ and Mn2+ ions co-doped highly transparent white-light emitting oxyfluoride glasses (precursor glass, PG) and Sr2LuF7 glass-ceramics (GC) were successfully prepared by the melt-quenching technique. Their luminescent and structural properties were investigated by the transmission spectra, excitation and emission spectra at different temperatures (300-500 K), luminescent decay curves, XRD, and TEM characterizations. Upon excitation with ultraviolet (UV) light, tunable broadband blue-white light emissions of Sn2+ were obtained by adjusting the concentration of Sn2+ ions. A conspicuous energy transfer process from Sn2+ to Mn2+ was observed in Sn2+/Mn2+ co-doped samples. Tunable broadband luminescence between blue-white light and orange-red light regions and nearly pink-white light emission was realized by varying Mn2+ concentration. Furthermore, compared to PG samples, the emissions were enhanced in GC samples due to the crystallization of Sr2LuF7 nanocrystals. Excellent thermal stability was also performed in these Sn2+ doped PG and GC samples with a recovering value of 96 % and 98.8 %, respectively. Simultaneously, Sn2+ doped PG and GC samples also own good optical thermal sensitivities with an SA value of 2.28 % and 2.47 % K-1, respectively. Our results indicate that these Sn2+/Mn2+ co-doped PG and GC may serve as tunable light sources under UV excitation and have prospects on the ratiometric optical thermometry fields.

A red-emitting phosphor Na3AlF6:Mn4+: Green synthesis, optical characteristics, thermal stability and application in high-performance warm WLED

Mn4+-doped fluoride red phosphors have been widely used in warm WLEDs, but the preparation of such phosphor requires the use of a large amount of HF as a fluorine source and an acidic environment. How to reduce the excessive use of highly toxic HF in the preparation process and achieve green synthesis has become a hot research topic. Therefore, a simple green synthesis strategy is proposed in this work to synthesize a series of red-emitting phosphors Na3AlF6:Mn4+. The highly toxic HF solution is replaced by using a low toxicity reaction system (HCl/HNO3 + NH4F), which reduces the direct use of HF. X-ray powder diffraction, energy-dispersive X-ray spectrometer and scanning electron microscope are employed to determine the crystal structure, composition and morphology of all samples. Optical properties are characterized using excitation spectra, emission spectra and fluorescence lifetime curves. The calculation results indicate that the red-light has low correlated color temperature and the excellent color purity, and Na3AlF6 host can provide a strong crystal field environment for Mn4+. In addition, different aluminum sources and Mn4+ doping concentrations are used to explore the optimal preparation condition. The mechanisms of concentration quenching and thermal quenching have also been systematically explored. The stabilities of red-light emission intensity and color are investigated under the high temperature. The integral PL intensity at 423 K is 47 % of the initial value at 298 K. The activation energy, the chromaticity shift and the chromaticity coordinate variation are also systematically calculated. More importantly, a high-performance warm WLED with low correlated color temperature (CCT = 3296 K) and high color rendering index (Ra = 94.7) is achieved by using Na3AlF6:Mn4+ as a red-emitting material. Not only that, the warm WLED exhibits strong output stability under high driving current. The discovery of this work provides a comprehensive understanding for the rational design of high-performance Mn4+-activated fluoride red phosphors via a simple green synthesis strategy.

Structure and Excitation Spectra of Third-Row Transition Metal Hexafluorides Based on Multi-Reference Exact Two-Component Theory.

The structures and some vertical excitation energies of third-row transition metal hexafluorides (MF6, M = Re, Os, Ir, Pt, Au, Hg) were calculated using the generalized-active-space configuration interaction (GASCI) theory based on the exact two-component (X2C) Hamiltonian. The spin-orbit coupling (SOC) was included at the Hartree-Fock level, enabling us to analyze the SOC at the orbital level (spinor-representation). The excitation spectra were assigned based on the double group, a relativistic group theory applicable to states with the SOC. This study provides a fundamental understanding of the ligand field splitting, including the SOC, that is useful for the photochemistry and spin chemistry involving heavy elements.

Sm3+ activated Ba3LaNa(PO4)3F fluorophosphate phosphor: Synthesis, characterization and their photoluminescence investigation for warm WLEDs

In this present research report, the series of Ba3LaNa(PO4)3Fphosphor doped with Sm3+ was successfully synthesized by using a high-temperature solid-state reaction method. The phase purity was examined using X-ray diffraction (XRD), which confirmed a pure phase of prepared material after sintering the sample at 700 °C. Fourier transform infrared (FT-IR) spectra showed absorption bands corresponding to the stretching and vibrational modes of PO4 in phosphate. Scanning electron microscopy (SEM) images displayed the morphology of sample and agglomerated structure of micron-sized particles. Photoluminescence excitation (PLE) and emission spectra of the Ba3LaNa(PO4)3F: Sm3+ phosphors were studied. When excited with near-UV light, the phosphor showed three prominent peaks at 567, 604, and 643 nm. The emission spectra for different concentrations of Sm3+ ions were also measured to find the optimal dopant concentration. The highest intensity was observed at a 2.0 mol% concentration of Sm3+ ions at 604 nmwith concentration quenching occurring beyond this point. The CIE chromaticity coordinates for the different concentration phosphor were located in the orange-red region, indicating its characteristic light emission. So therefore, these results suggested that the synthesized reddish-orange light-emitting Ba3LaNa(PO4)3F: Sm3+prepared phosphor is promising for applications in white light-emitting diodes (WLEDs).

Study on the properties of Sm3+-Doped CaTbAl3O7 phosphors

New single phase and adjustable emission phosphors have attracted a lot of attention because of the good luminous properties. In this work, Sm3+ doped CaTbAl3O7 phosphors are prepared in air by solid-state method. The crystal structure, concentration dependent spectra, lifetimes, and luminescence properties are investigated. Because of the 4f8 → 4f75d1 and 4f → 4f transitions of Tb3+ ion, host (CaTbAl3O7) shows an excitation spectrum in the range of 220–520 nm under monitored at 544 nm and emits yellow-green light under excitation 248, 284, and 368 nm due to the 5D4 → 7FJ (J = 0, 1, 2, 3, 4, 5, and 6) transitions of Tb3+ ion. CaTbAl3O7:Sm3+ under monitored 598 nm contains the excitation spectral peaks of both CaTbAl3O7 and Sm3+ ion. With excitation at 368 nm, CaTbAl3O7:Sm3+ glows orange-red light, its PL spectrum has both host (CaTbAl3O7) and Sm3+ ion contributing, and the chromaticity coordinates are about (0.5499, 0.4351). Under excitation 402 nm, the red-orange emission of CaTbAl3O7:Sm3+ is only the contribution of Sm3+ ion and the chromaticity coordinates are about (0.5823, 0.4168). The energy transfer process from Tb3+ in host (CaTbAl3O7) to Sm3+ ions can be confirmed via the spectral properties. We explain the luminous mechanism of CaTbAl3O7:Sm3+ by the energy level diagrams of Tb3+ and Sm3+.

Generating interstitial water within the persisting tetrahedral H-bond network explains density increase upon compressing liquid water

Despite its ubiquitous nature, the atomic structure of water in its liquid state is still controversially debated. We use a combination of X-ray Raman scattering spectroscopy in conjunction with ab initio and path integral molecular dynamics simulations to study the local atomic and electronic structure of water under high pressure conditions. Systematically increasing fingerprints of non-hydrogen-bonded H[Formula: see text]O molecules in the first hydration shell are identified in the experimental and computational oxygen K-edge excitation spectra. This provides evidence for a compaction mechanism in terms of a continuous collapse of the second hydration shell with increasing pressure via generation of interstitial water within locally tetrahedral hydrogen-bonding environments.

Interferometric excitation fluorescence lifetime imaging microscopy

Fluorescence lifetime imaging microscopy (FLIM) is a well-established technique with numerous imaging applications. Yet, one of the limitations of FLIM is that it only provides information about the emitting state. Here, we present an extension of FLIM by interferometric measurement of fluorescence excitation spectra. Interferometric Excitation Fluorescence Lifetime Imaging Microscopy (ixFLIM) reports on the correlation of the excitation spectra and emission lifetime, providing the correlation between the ground-state absorption and excited-state emission. As such, it extends the applicability of FLIM and removes some of its limitations. We introduce ixFLIM on progressively more complex systems, directly compare it to standard FLIM, and apply it to quantitative resonance energy transfer imaging from a single measurement.

Quasi-boson approximation yields accurate correlation energy in the 2D electron gas

We report the successful adaptation of the quasi-boson approximation, a technique traditionally employed in nuclear physics, to the analysis of the two-dimensional electron gas. We show that the correlation energy estimated from this approximation agrees closely with the results obtained from quantum Monte Carlo simulations. Our methodology comprehensively incorporates the exchange self-energy, direct scattering, and exchange scattering for a particle-hole pair excited out of the mean-field ground state within the equation-of-motion framework. The linearization of the equation of motion leads to a generalized random phase approximation (gRPA) eigenvalue equation whose spectrum indicates that the plasmon dispersion remains unaffected by exchange effects, while the particle-hole continuum experiences a marked upward shift due to the exchange self-energy. Using the gRPA excitation spectrum, we calculate the zero-point energy of the quasi-boson Hamiltonian, thereby approximating the correlation energy of the original Hamiltonian. This research highlights the potential and effectiveness of applying the quasi-boson approximation to the gRPA spectrum, a fundamental technique in nuclear physics, to extended condensed matter systems. Published by the American Physical Society 2024

Fabrication and Characterization of Ce3+-Doped Lithium Alumino-Silicate Scintillating Glass-Ceramic and Fiber.

Ce3+-doped lithium alumino-silicate (Li-Al-Si) scintillating glass was prepared using a melting method and crystallized via heat treatment. X-ray diffraction and transmission electron microscopy confirmed the presence of nanocrystals in the materials. Radioluminescence spectra, obtained by X-ray excitation, and luminescence spectra, obtained by 338 nm excitation, showed that the luminescence intensity increased after crystallization. The glass was combined with pure silica as the inner cladding to fabricate a hybrid fiber core using a melt-in-tube technique. The composition of the fiber core was examined using an electron probe microanalyzer. The glass fiber produced strong blue luminescence under UV excitation. After a micro-crystallizing heat treatment of the hybrid fiber at 850 °C in a reducing atmosphere, a Ce3+-doped lithium alumino-silicate glass-ceramic scintillating hybrid fiber was obtained. The nanocrystal structure of the fiber core was examined using micro-Raman spectroscopy. Excitation and luminescence spectra of the hybrid fiber before and after micro-crystallization were measured using microspectrofluorimetry. The results demonstrated that the fiber remained luminous after micro-crystallization. Hence, this work provides a new way to prepare scintillating glass-ceramic hybrid fibers for neutron detection.

Development of Mg2TiO4:Mn4+ phosphors for enhanced red LED emission and forensic fingerprint analysis

The advancement in the development of inorganic phosphors marks a significant milestone in the fields of LED technology and forensic science. Herein, Mg2TiO4:Mn4+ (MTO:Mn4+) novel red-emitting phosphors are synthesized through a solvothermal method, which demonstrates a promising approach for enhancing latent fingerprint detection capabilities and improving the performance of red LEDs. The confirmation of the cubic structure post-annealing and the nano-nature as revealed by TEM analysis underpin the MTO:Mn4+ phosphors suitability for these applications. The broad excitation spectra and the sharp red emission at 659 nm, coupled with the optimal doping concentration, showcase the MTO:Mn4+ phosphor's efficient luminescence properties. Moreover, the calculated critical distance between Mn4+ ions (32.906 Å) elucidates the concentration quenching mechanism, which is pivotal for optimizing the performance. The high purity of the emitted red light (97.2 %) and the precise CIE coordinates (0.5969, 0.2926) of the MTO:Mn4+ phosphor suggest its potential for producing high-quality red LEDs. Additionally, the capability of MTO:Mn4+ phosphors to reveal detailed and high-resolution latent fingerprints offers a more reliable and efficient method for processing and analyzing crucial evidence. These findings not only contribute to the scientific understanding of MTO:Mn4+ phosphor materials but also pave the way for their practical application in cutting-edge technologies.

Fast and Artifact-Free Excitation Multiplexing Using Synchronized Image Scanning.

Multicolor fluorescence microscopy is an essential tool to visualize structures and dynamics in the life and materials sciences. However, the near-simultaneous acquisition of labels differing in excitation spectrum is difficult and renders such measurements prone to artifacts. We present a simple strategy to provide quasi-simultaneous fluorescence imaging with multiple excitation wavelengths by using an optical element to displace the sample image on the sensor at a rate that is much faster than the image acquisition rate and synchronizing this with the illumination. The emission elicited by the different wavelengths can then be encoded into the point-spread function of the imaging or visualized as multiple distinct images. In doing so, our approach can eliminate or mitigate artifacts caused by temporal aliasing in conventional sequential imaging. We demonstrate the use of our system to uncover hidden emissive states in single quantum dots and for the imaging of Ca2+ signaling in neurons.

Colour tunability of Dy3+ & Sm3+ activated yttrium aluminium gallium nanocrystals for display applications

A set of powder samples of Y3AlGa4O12 doped with Dy3+ and Sm3+ with different concentration of Sm3+ ion were prepared via sol-gel synthesis. X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive (EDS), Fourier transform infrared (FTIR) and photoluminescence spectral studies were carried out. All the diffraction peaks matched the cubic lattice Y3AlGa4O12, as given by the XRD. The SEM images revealed aggregated spherical particles ranging from 50 to 130 nm. The EDS analysis confirmed the presence of the initial chemicals in the synthesized samples. FTIR spectrum was used to examine the vibrational modes in the sample. Under a 366 nm excitation wavelength, the emission spectrum showed the peaks at 492 nm (blue), 580 nm (yellow), 673 nm (red), and 760 nm (near-infrared) corresponding to the characteristic transitions 4F9/2 → 6H15/2,13/2,11/2,9/2 of the Dy3+ ion, respectively. In comparison, the peaks at 568 nm, 614 nm, 664 nm, and 711 nm corresponded to the characteristic transitions 4G5/2 → 6H5/2,7/2,9/2,11/2 of the Sm3+ ion. Under near ultraviolet light excitation, the superposition of these blue, yellow and red colours produced excellent white light emission. The intensities of these transitions varied with the concentration of Sm3+ ion and the excitation wavelength. The emission spectrum of Dy3+ overlapped with the excitation spectrum of Sm3+, indicated possible energy transfer from Dy3+ to Sm3+. According to Inokuti-Hirayama's theory of energy transfer, the mechanism of energy transfer was understood to be quadrupole-quadrupole interaction. The CIE chromaticity co-ordinates and correlated colour temperature values showed that these samples were suitable for light-emitting diode applications.