Measurements Of Emission Spectra Research Articles

Resonant inelastic x-ray scattering in warm-dense Fe compounds beyond the SASE FEL resolution limit

Resonant inelastic x-ray scattering (RIXS) is a widely used spectroscopic technique, providing access to the electronic structure and dynamics of atoms, molecules, and solids. However, RIXS requires a narrow bandwidth x-ray probe to achieve high spectral resolution. The challenges in delivering an energetic monochromated beam from an x-ray free electron laser (XFEL) thus limit its use in few-shot experiments, including for the study of high energy density systems. Here we demonstrate that by correlating the measurements of the self-amplified spontaneous emission (SASE) spectrum of an XFEL with the RIXS signal, using a dynamic kernel deconvolution with a neural surrogate, we can achieve electronic structure resolutions substantially higher than those normally afforded by the bandwidth of the incoming x-ray beam. We further show how this technique allows us to discriminate between the valence structures of Fe and Fe2O3, and provides access to temperature measurements as well as M-shell binding energies estimates in warm-dense Fe compounds.

Experimental study on the discharge characteristics of an air rotating gliding arc

In this study, the discharge characteristics of an air rotating gliding arc (RGA) are investigated by synchronous measurements of a digital oscilloscope and a high-speed camera, and the emission spectrum measurement. The discharge evolution in one complete motion cycle exhibits a ‘breakdown-elongation-extinction’ process accompanied by a jump phenomenon of the arc root and a back-breakdown phenomenon. The discharge evolves from the unstable breakdown mode (U-B), to the transition mode and finally to the stable gliding mode (S-G) by increasing the input voltage or decreasing the tangential and axial gas flow rates. The U-B mode at an input voltage of 120 V is featured by the large reduced electric field and high electron temperature of 1.90 eV, but the arc length and existence time are very short. The S-G mode at an input voltage of 270 V has a relatively low breakdown frequency of 0.33 kHz and an average breakdown current of 1.31 A, implying that the arc steadily glides and rotates along the spiral electrode. The average electron temperature is 0.64 eV in the S-G mode, while the arc length and existence time are longer. The rotational and vibrational temperatures of the N2(C3∏u) state are respectively measured at 2200 K and 4400 K in the U-B mode, and in the S-G mode are 2600 K and 4820 K. From the evolution of emission intensities of measured excited species, it is found that the NOγ band emission intensity generally rises from the U-B mode to the S-G mode since the gas temperature and arc existence time rise, indicating that the S-G mode may be beneficial for the vibrationally promoted Zeldovich reactions. This study could deepen the understanding of arc characteristics in air RGA for selecting a suitable mode to achieve better plasma performance in practical applications.

The tri-band high spectral resolution spectrometer with gratings in tandem for the charge-exchange recombination spectroscopy diagnostic system on HL-2A tokamak

Charge-exchange (CX) recombination spectroscopy is a powerful tool monitoring ion temperature and plasma rotation with good temporal and spatial resolutions. A compact, new design for a high-throughput, tri-band high spectral resolution spectrometer has been developed for the charge-exchange recombination spectroscopy measurement on the HL-2A tokamak. The simultaneous measurements of He II (468.57 nm), C VI (529.1 nm), and Dα (656.1 nm accompanied by beam emission spectra) with an acquisition frequency up to 400 Hz are achieved by vertically binning the spectrum from each fiber in experiments. Initial results indicate that the system can provide radial profiles of not only ion temperature and rotation velocity, but also concentration of carbon. For the case of helium, the measurements for the ion temperature and rotation velocity are straightforward but the apparent concentration associated with the observed CX intensity is obviously too high. Modeling of the active He II CX feature including plume contributions needs to be carried out to extract the true helium concentration. The spectrometer could become a prototype for the ITER charge-exchange recombination spectroscopy diagnostic and the pilot experiments, as presented here, demonstrate the possibility of impurity concentrations measurements based on the combined measurement of local beam emission and charge-exchange recombination spectroscopy spectra.

Channeling of fluorescence photons from quantum dots into guided modes of an optical nanofiber tip

We demonstrate the channeling of fluorescence photons from quantum dots (QDs) into guided modes of an optical nanofiber tip (ONFT). We deposit QDs on the ONFT using micro/nano fluidic technology. We measure the photon-counting and emission spectrum of fluorescence photons that are channeled into guided modes of the ONFT. The measured emission spectrum confirms the deposition of QDs on the ONFT. We perform numerical simulations to determine channeling efficiency (η) for the ONFT and a single dipole source (SDS) system. For the radially oriented SDS at the center of the facet of the ONFT, we found the maximum η-value of 44% at the fiber size parameter of 7.16, corresponding to the ONFT radius of 0.71 µm for the emission wavelength at 620 nm. Additionally, we investigate the SDS position dependence in transverse directions on the facet of the ONFT in view of keeping experimental ambiguities. The present fiber inline platform may open new avenues in quantum technologies.

Measurement of Fe emission spectrum from 170 nm to 600 nm with a coma-free spectrometer

A coma-free superhigh spectral resolution optical spectrometer was successfully designed and constructed for practical application.

Investigation of Praseodymium Ions Dopant on 9/65/35 PLZT Ceramics’ Behaviors, Prepared by the Gel-Combustion Route

In this work, were synthesized (Pb0.91La0.09)(Zr0.65Ti0.35)0.9775O3 ceramic materials with different concentrations of praseodymium (0, 0.1, 0.3, 0.5, 1 wt.%) via gel-combustion route and sintered by the hot uniaxial pressing method. Measurements were conducted on the obtained ceramics using X-ray powder diffraction (XRD), scanning electron microscope (SEM), EDS analysis, and examination of dielectric and ferroelectric optical properties. Results give us a detailed account of the influences of the praseodymium ions on the structural, microstructural, and dielectric properties. 3D fluorescence maps and excitation and emission spectra measurements show how a small admixture changes the ferroelectric relaxor behavior to an optically active ferroelectric luminophore.

Fluorescence Quenching and the Chamber of Nitroaromatics: A Dinaphthoylated Oxacalix[4]arene's (DNOC) Adventure Captured through Computational and Experimental Study.

This research presents the application of Dinaphthoylated Oxacalix[4]arene (DNOC) as a novel fluorescent receptor for the purpose of selectively detecting nitroaromatic compounds (NACs). The characterization of DNOC was conducted through the utilization of spectroscopic methods, including 1H-NMR, 13C-NMR, and ESI-MS. The receptor demonstrated significant selectivity in acetonitrile towards several nitroaromatic analytes, such as MNA, 2,4-DNT, 2,3-DNT, 1,3-DNB, 2,6-DNT, and 4-NT. This selectivity was validated by the measurement of emission spectra. The present study focuses on the examination of binding constants, employing Stern-Volmer analysis, as well as the determination of the lowest detection limit (3σ/Slope) and fluorescence quenching. These investigations aim to provide insights into the inclusion behavior of DNOC with each of the six analytes under fluorescence spectra investigation. Furthermore, the selectivity trend of the ligand DNOC for NAC detection is elucidated using Density Functional Theory (DFT) calculations conducted using the Gaussian 09 software. The examination of energy gaps existing between molecular orbitals, namely the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), provides a valuable understanding of electron-transfer processes and electronic interactions. Smaller energy gaps are indicative of heightened selectivity resulting from favorable electron-transfer processes, whereas bigger gaps suggest less selectivity attributable to weaker electronic contacts. This work integrates experimental and computational methodologies to provide a full understanding of the selective binding behavior of DNOC. As a result, DNOC emerges as a viable chemical sensor for detecting nitroaromatic explosives.

Joint measurement of electron density, temperature, and emission spectrum of Nd:YAG laser-produced tin plasma

We present the results of joint measurements of electron density (ne), temperature (Te), and emission spectra of an Nd:YAG-driven tin plasma. Collective Thomson scattering provides space- and time-resolved ne and Te data during drive laser irradiation, and extreme ultraviolet (EUV) emission spectra, which is space-resolved in the target normal, are measured using a flat-field grazing incidence spectrometer (GIS). As the distance from the target increased, the emission intensity quickly decreases, and the peaks of the spectra gradually shift to longer wavelengths. This can be explained by the rapid decrease in ne, and thus, self-absorption, with an increase in distance. We obtain the EUV spectra by calculating the transfer of photons along the line-of-sight of the GIS, using theoretical emissivity and opacity, and applying the measured spatial distribution of ne and Te. The results quantitatively demonstrate that the self-absorption effect is significant; the emission from the core regions is mostly reabsorbed by the surrounding plasma. The calculated spectra are compared with the measured spectra. While good agreement is achieved in the spectral region of 13.3 and 15.3 nm, considerable differences are found in the 12.5–13 and 15.5–17.5 nm region. The results demonstrate the significance of this joint measurement for further validation of the atomic process model considering self-absorption effect, which is critical for the future high-density, solid laser-driven EUV source.

Considerations for determining the performance of ultraviolet light emitting diode fluid disinfection systems.

The International Ultraviolet Association (IUVA) Task Force was formed to develop guidelines regarding testing and reporting on performance of UV LED water disinfection systems. The goal was to provide clarity in a guidance document on measuring system performance across the global UV LED water disinfection system market. A review of current performance measurement protocols for mercury lamp based systems shows that the common elements of UV LED system performance measurement protocols should be as follows: specified standard for the amount of pathogen reduction required, the requirement that the validation testing be conducted by a competent facility, and that the system be continually monitored by UV sensors while in use to verify system performance unless pathogen reduction is not claimed. UV LEDs have selectable peak wavelengths, as opposed to mercury lamps that have fixed emission wavelength values. As a result of this difference, the following changes to protocols used to test mercury lamp systems are recommended. First, the use of disinfection benchmarks other than 254 nm dose, such as direct inactivation values, dose benchmarks referenced to 254 nm, and/or dose benchmarks at the UV LED emission wavelength that give the same inactivation as the original 254 nm UV dose benchmark. Second, the use of 254 nm UV water transmittance values as a placeholder, rather than an assumed correct value, for systems under test with LED wavelengths >250 nm and water transmittance values ≥87%. More research is needed for lower wavelengths and UVTs. Third, the recommendation that germicidal response UV sensors be used in UV LED based systems to ensure that the validated disinfection is delivered. Finally, additional LED-specific considerations were also noted. UV LEDs are also instant-on devices, making them ideal light sources for systems operated intermittently. Performance testing of systems operated intermittently should include a test to insure that pathogens do not migrate past the UV LEDs while the LEDs are off. UV LED devices have recognized protocols for determining the lifetime of the devices, as well as for measuring other device properties. Caution should be exercised in using these lifetime values for devices in UV disinfection systems, since the thermal environment of the devices may be different for protocol testing and disinfection system operation. PRACTITIONER POINTS: Validation of UVC LED fluid disinfection is necessary for point of use, point of entry, and municipal applications. The emission spectrum properties, considerations and measurements for output over lifetime, and unique system design considerations of UVC LEDs as light sources are factors that must be considered when evaluating fluid disinfection performance. The instant-on operation, system geometry, validation benchmarks, system sensing, water transmittance, and fouling must also be considered for UVC LED devices when evaluating fluid disinfection performance.

Structural, spectroscopic properties ant prospective application of a new nitropyridine amino N-oxide derivative: 2-[(4-nitropyridine-3-yl)amino]ethan-1-ol N-oxide

A new nitropyridine amino N-oxide derivative 2-[(4-nitropyridine-3-yl)amino]ethan-1-ol N-oxide was synthesized and its structural and optical properties were described. Its structure obtained from the X-ray diffraction (XRD) studies was related to the Infrared spectroscopy (IR), Raman spectroscopy (RS), electron Ultraviolet–Visible spectroscopy (UV–VIS) and emission spectra measurements. The experimental results were analyzed in terms of theoretical data obtained from quantum chemical Density Functional Theory (DFT) and Natural Bond Orbital (NBO) calculations. The 6-311G(2d,2p) basis set with the B3LYP functional was used to discuss its optimized structure and vibrational properties. Femtosecond excitation was used to recognize the depopulation mechanism of the electron excited states in the studied compound. It was found that the intermolecular interactions strongly influence the physicochemical properties and application of the new nitropyridine amino N-oxide derivative.

Down-/Up-conversion luminescence behaviors and energy transfer analysis in Tm3+ and Tm3+/Yb3+ co-doped tellurite glasses

Glasses with the chemical composition of (50-x-y) TeO2-30ZnO-10YF3-10NaF-0.5Tm2O3-yYb2O3 (y = 0.5, 1.0, and 3.0 mol%) are developed using a melt-quenching method. Measurements of absorption, excitation, down and up-conversion emission spectra, and decay times were used to investigate the energy transfer processes. Cross-relaxation mechanisms caused the emission intensity to decrease at higher Tm3+ ion concentrations. The Tm3+/Yb3+ co-doped glasses showed strong up-conversion emission under the diode laser excitation at 978 nm. Studies on the dependence of pump energy revealed the mechanism underlying the up-conversion luminescence. According to the findings, the developed Tm3+/Yb3+co-doped glasses are also found to be a promising option for spectral conversion and emission (visible and near infrared) applications.

Injection of metallic elements into an electron-beam ion trap using an electron impact metal vapor source

We demonstrate a versatile method for injecting metallic elements into an electron-beam ion trap using a metal vapor source. This method is based on the evaporation of a metal target by continuous electron-beam impact. We present visible emission spectra of highly charged tungsten ions prepared by the present injection scheme. By comparison with the conventional injection method using a high-vapor-pressure W(CO)6 compound, several advantages of the present method, i.e. suppressing charge exchange reactions in the trap region and quick recovery of the vacuum condition after stopping the injection, are found. The present injection method also facilitates the measurement of emission spectra of highly charged niobium ions, which have never previously been observed using electron-beam ion traps.

Deep insight on two luminous mechanism and optical properties of Pr doped MgGeO3 red/NIR luminescent materials

In this work, MgGeO3:Pr3+ system is prepared by high-temperature solid phase method under the condition of different temperature and Pr content. MgGeO3:Pr3+ could emit 622 nm (red), 716 nm (red), 903 nm (NIR) and 1081 nm (NIR) lights under the external excitation of 251 nm and 425–500 nm. Due to the different excitation wavelengths, MgGeO3:Pr3+ has completely different electronic transition paths, resulting in a much larger emission intensity under 251 nm excitation than that excited by 425∼500 nm. When the incident light wavelength is 251 nm, the excitation process is VB→1D2 level of Pr3+, and the emission is due to transition of 1D2→3H4, 1D2→3H5, 1D2→3H6(3F2) and 1D2→3F3,4. When the wavelength of incident light is 425∼500 nm, the excitation process is 3H4→CB, the emission is CB→1D2, and then 1D2→3H4, 1D2→3H5, 1D2→3H6(3F2) and 1D2→3F3,4. At the same time, the emission spectrum and X-ray diffraction measurements show that the most fundamental factor determining the emission intensity of the sample is the concentration of the luminescent center (Pr3+ that can emit light) in the MgGeO3 grain. Increasing the sintering temperature and Pr element content in raw materials can increase the of Pr3+ concentration in the grain (increase the concentration of the luminescent center). However, if the concentration of Pr3+ in the grain is too high, Pr3+ would lose the function of the luminescence center, resulting in a decrease in the concentration of the luminescence center, thereby reducing the luminescence intensity.

Simple method for determining quantum efficiency and background propagation loss in thulium-doped fibres

A method for determining the quantum efficiency and background propagation loss in rare earth-doped silica fibres is presented. These parameters can be determined using straightforward measurements of slope efficiency and emission spectra at various lengths of active fibre. This method has been applied to a thulium-doped silica fibre with a structured ‘nested-ring’ doping profile. The quantum efficiency of this fibre was 1.93 ± 0.01 and the background propagation loss was 0.15 ± 0.01 dB/m. This characterisation method also allows the relative impact of these parameters on the slope efficiency of an all-fibre high-power system to be predicted. It was found that the non-ideal background propagation loss of this fibre results in a decrease of sim 18 percentage points on the predicted slope efficiency, whereas the quantum efficiency results in a decrease of sim 3 percentage points. The predicted slope efficiency with respect to absorbed pump power of 62 ± 2% for the all-fibre high-power system is consistent with the experimental result of 61.5%. This characterisation provides feedback to the fibre design and fabrication that for efficient power scaling, efforts to decrease the background propagation loss of this fibre can provide a greater increase in efficiency than efforts to further increase the quantum efficiency.

Improving performance prediction of diode end-pumped solid-state Nd:YAG rod amplifiers by incorporating pump mode evolution.

Master Oscillator Power Amplifier (MOPA) systems find extensive use in laser development to increase the optical power of laser emissions from a Master Oscillator (MO). Commonly used are the cylindrical rod MOPAs that are optically excited using a multimode fiber-coupled (FC) diode laser emission in an end-pumped configuration. Current analytical 3D models that incorporate thermal effects, gain saturation, and iterative Fourier beam propagation methods, collectively, rely on static approximations of the evolution of the FC pump beam profile over the longitudinal volume of the amplifier crystal. Furthermore, in general, the spectral behavior of the FC diode emission is assumed to be static, and the thermal wavelength shift is not accounted for in the simulation. In this work, we demonstrate a novel approach for accurate modeling of the multimode FC pump beam emission as a complex field using a phase-only Gaussian to flat-top (FT) diffractive optical element, thus allowing for the inclusion of the pump beam into the iterative propagation method. Additionally, we present a method for precise calibration of the model using simple experimental measurements of the diode emission spectrum. The theoretical model is experimentally validated using an end-pumped Nd:YAG crystal rod to perform single-pass amplification of a Gaussian beam, showing excellent agreement with predicted output powers over the calibrated range of pump powers. Furthermore, we provide experimental data that exhibits a strong correlation between the Gaussian to FT phase-only transformation and the multimode FC diode evolution in free-space propagation.

High-Throughput Characterization of Single-Quantum-Dot Emission Spectra and Spectral Diffusion by Multiparticle Spectroscopy

In recent years, quantum dots (QDs) have emerged as bright, color-tunable light sources for various applications such as light-emitting devices, lasing, and bioimaging. One important next step to advance their applicability is to reduce particle-to-particle variations of the emission properties as well as fluctuations of a single QD’s emission spectrum, also known as spectral diffusion (SD). Characterizing SD is typically inefficient as it requires time-consuming measurements at the single-particle level. Here, however, we demonstrate multiparticle spectroscopy (MPS) as a high-throughput method to acquire statistically relevant information about both fluctuations at the single-particle level and variations at the level of a synthesis batch. In MPS, we simultaneously measure emission spectra of many (20–100) QDs with a high time resolution. We obtain statistics on single-particle emission line broadening for a batch of traditional CdSe-based core–shell QDs and a batch of the less toxic InP-based core–shell QDs. The CdSe-based QDs show significantly narrower homogeneous line widths, less SD, and less inhomogeneous broadening than the InP-based QDs. The time scales of SD are longer in the InP-based QDs than in the CdSe-based QDs. Based on the distributions and correlations in single-particle properties, we discuss the possible origins of line-width broadening of the two types of QDs. Our experiments pave the way to large-scale, high-throughput characterization of single-QD emission properties and will ultimately contribute to facilitating rational design of future QD structures.

Combustion synthesized novel SrAlBO4:Eu3+ phosphor: Structural, luminescence, and Judd-Ofelt analysis

A series of new phosphor SrAlBO4 doped by Eu³+ was synthesized by using very known Combustion method. The structural and optical properties explored using X-ray diffraction (XRD). The XRD pattern was matched well with the standard PDF card no. 1542236.The obtained phosphor had orthorhombic structure with space group Pccn (56). The image of Scanning electron microscope shows the external morphology of SrAlBO4 phosphor material, which revails the irregular morphology and the material showed the non uniform structure with agglomerates' size was size ranging in several micrometers. The confirmation of present element and their percentage also shown in the EDX image. The luminescence properties of rare earth activated SrAlBO4 phosphor were determined by measurement of excitation and emission spectra. The PL emission spectra of Eu3+ doped SrAlBO4 phosphor show characteristics bands at 590 nm & 614 nm which corresponds due to 5D0 →7F1 and 5D0 →7F2 transition of Eu3+ ions upon 395 nm excitation. The effect of different concentration of Eu3+ on luminescence emission intensity of SrAlBO4 phosphor was also studied. Further, concentration quenching is explained using Blasse's equation and Dexter's theory. Also, Judd-Ofelt analysis was performed on photoluminescence emission spectra. On investigation synthesized rare earth activated SrAlBO4 phosphor can be suitable for all lighting application devices.

Synthesis and photophysical properties of fluorescent 8,9‐diarylbenzo[def]carbazoles

AbstractBackgroundBenzocarbazole has attracted much attention from scientists in the past few decades for a variety of applications in materials science.ObjectiveHerein we report the synthesis and photophysical properties of N‐acyl and N‐free 8,9‐diarylbenzo[def]carbazoles.MethodsThese benzo[def]carbazoles were prepared by Pd(II)‐catalyzed C‐H bond activation and deacetylation as the key steps, and their photophysical properties were studied by measurement of absorption and emission spectra in chloroform at room temperature.ResultsThe 8,9‐diarylbenzo[def]carbazoles show lower LUMO energy levels and smaller HOMO/LUMO gap compared to the parent benzo[def]carbazole, and the N‐unprotected 8,9‐diarylbenzo[def]carbazoles show more red‐shifted fluorescent emission compared to the N‐acyl ones. The absorption and emissionmaxima of these 8,9‐diaryl‐substituted benzo[def]carbazoles in CHCl3 were in the ranges of 278–350 and 365–426 nm, respectively, and with quantum yields (ΦF) up to 0.62.ConclusionsWe have demonstrated the photophysical properties of 8,9‐diaryl substituted benzo[def]carbazoles with or without N‐acetyl group. These 8,9‐diaryl substituted benzo[def]carbazoles could be good candidates for the future development of functional organic molecules.

Measurements and Modeling of Air Plasma Radiation in the VUV

Measurements of high-temperature air emission spectra between 150 and 250 nm (VUV/UV) are presented. These measurements are calibrated in absolute intensity. The high-temperature air was produced using an atmospheric pressure plasma torch facility. The centerline temperature of the plasma jet is approximately 6700 K. A VUV emission spectroscopy system was adapted to the plasma torch facility to acquire spectra from 150 to 250 nm. Absolute intensity spectra were obtained in this wavelength range. They were compared with numerical predictions of the line-by-line spectroscopy code SPECAIR. The overall agreement between the SPECAIR predictions and measurements is good, particularly above 180 nm. Several modifications to the SPECAIR radiation code were carried out in order to improve agreement with experiments. These modifications significantly improved agreement though, at lower wavelengths, the data indicate that a source of emission remains unaccounted for by SPECAIR. Several possibilities for this missing source of emission are discussed, including photodissociation of the nitric oxide molecule.

Growth and Characterization of All-Inorganic Halide Perovskite CsPbF3 Single Crystals

Lead-based halide perovskite semiconductors have demonstrated considerable potential in optoelectronic applications. However, the lack of high-quality crystals suitable for research has led to rare reports on CsPbF3 single crystals. Good quality CsPbF3 single crystals were successfully grown using the Bridgman method. The structure, luminescence, and electrical properties of crystals were investigated. At room temperature, the crystal structure was determined to be cubic perovskite, with a calculated bandgap of 3.68 eV. The measured emission spectrum showed one broad emission peak at approximately 400 nm. Three decay time constants were obtained from a sum of exponential functions fit to the fluorescence decay curve: 0.4 ns, 2.4 ns, and 15.0 ns for fast, middle, and slow decay times, respectively. The decay times excited by pulsed X-ray were measured to be 2.2 ns and 10.2 ns, indicating that CsPbF3 is an ultrafast scintillator. Furthermore, the electrical properties demonstrated that CsPbF3 exhibits high ion mobility, which is approximately 20 times that of electron mobility.