Experimental Lifetimes Research Articles

Substrate effect on excitonic shift and radiative lifetime of two-dimensional materials

Substrates have strong effects on optoelectronic properties of two-dimensional (2D) materials, which have emerged as promising platforms for exotic physical phenomena and outstanding applications. To reliably interpret experimental results and predict such effects at 2D interfaces, theoretical methods accurately describing electron correlation and electron-hole interaction such as first-principles many-body perturbation theory are necessary. In our previous work (2020 Phys. Rev. B 102 205113), we developed the reciprocal-space linear interpolation method that can take into account the effects of substrate screening for arbitrarily lattice-mismatched interfaces at the GW level of approximation. In this work, we apply this method to examine the substrate effect on excitonic excitation and recombination of 2D materials by solving the Bethe–Salpeter equation. We predict the nonrigid shift of 1s and 2s excitonic peaks due to substrate screening, in excellent agreements with experiments. We then reveal its underlying physical mechanism through 2D hydrogen model and the linear relation between quasiparticle gaps and exciton binding energies when varying the substrate screening. At the end, we calculate the exciton radiative lifetime of monolayer hexagonal boron nitride with various substrates at zero and room temperature, as well as the one of WS2 where we obtain good agreement with experimental lifetime. Our work answers important questions of substrate effects on excitonic properties of 2D interfaces.

Ag nanoparticle enhanced radiative behaviour of Eu3+ ions in sol-gel silica matrix

AgNP doped Eu SiO2 glasses were prepared by the sol-gel method with fixed Eu3+ and varying Ag concentrations. The samples have been characterized structurally by XRD, SEM, EDX and TEM. The effects of incorporation of AgNPs on the radiative properties of the Eu3+ in SiO2 matrix are studied with the help of Absorption and Photoluminescence Spectroscopy. Various radiative parameters like oscillator strength, Judd Ofelt intensity parameters, spontaneous emission probabilities, branching ratio, radiative lifetime, emission cross-section etc. are calculated from the observed absorption and photoluminescence spectra using Judd Ofelt theory, whereas the experimental lifetime of 5D0 state of Eu3+ ion and colour chromaticity is estimated from lifetime and CIE 1931 colour chromaticity measurements. The observed enhancement in the absorption and emission intensities of Eu3+ ions are elucidated in the light of enhanced local field in the vicinity of the AgNPs due to the LSPR effect and also the network modifying role of AgNPs.

Heterogeneous bi-directional recurrent neural network combining fusion health indicator for predictive analytics of rotating machinery

Data-driven intelligent methods arise the increasing demand for predictive analytics to evaluate the operational reliability and natural degradation of rotating machinery. Nevertheless, accurate and timely predictive analytics is still regarded as an extremely challenging mission, because the quality of predictive maintenance depends not only on the capability of intelligent model, but also on the construction of effective health indicators To overcome this issue, a novel heterogeneous bi-directional gated recurrent unit (GRU) model combining with fusion health indicator (Fusion-HI) is proposed for predictive analytics in this paper. First, the support evidence space is constructed to reflect the operating state of mechanical equipment. Then the evidence features from multiple domains are integrated to obtain the optimal Fusion-HI by the modified de-noising auto-encoder (MDAE). Finally, a hybrid prediction network is designed combining with the gate attention algorithm, which consists of multi-scale convolution layers, bi-directional GRU layers, smoothed and de-noised layers, and regression layers. Three experimental whole lifetime data and one industrial entire life cycle data are analyzed to validate the feasibility of the proposed approach in two case studies respectively. Relevant experimental results indicate that the Fusion-HI is capable to sensitively characterize the degradation state of equipment, while the prediction accuracy of presented heterogeneous model is superior to that of conventional prediction approaches.

Investigations on the luminescence and gamma ray shielding features of Pr3+: BLCZFB glass for orange-red laser and radiation applications

Praseodymium (Pr3+) ions doped barium lithium calcium zinc fluoroborate (BLCZFB) glasses were prepared with the melt quenching technique, and their physical, optical, and shielding properties were estimated. Their amorphous nature was verified with X-ray diffraction (XRD) pattern. Each of their absorption spectra exhibited nine peaks in the visible and near infra-red (NIR) regions. The absorption bands of oscillator strength and Judd-Ofelt (J-O) parameters were used to evaluate their radiative parameters. Their predominant emission peak in their visible emission spectra was observed at 604 nm (16556 cm−1), attributed to 1D2→3H4 transition. And their main emission peak in the NIR emission spectra was at the wavelength of 1458 nm (6858 cm−1), corresponding to the 1D2→1G4 transition. Their spectroscopic properties, including the stimulated emission cross-section (σPE), branching ratio (βR), quantum efficiency (η), gain bandwidth (σPE×Δλeff), and optical gain parameter (σPE×τexp) were also calculated for the visible (1D2→3H4) and NIR (1D2→1G4) emission transitions. From their emission spectra, the color chromaticity coordinates, (x, y) and (u, v), the color purity (CP), and the correlated color temperature (CCT) were calculated. The concentration quenching mechanism and energy transfer process were also explored from the emission spectra. Both the visible and the NIR lifetime curves exhibited non-exponential behaviour for all the glasses. The experimental lifetime decreases with the increase of Pr3+ ions concentration, which could be attributed to the cross-relaxation channels. The decay profiles are well fitted with Inokuti-Hirayama (IH) model (S = 6) to realize the energy transfer process. The energy transfer parameter (Q), donor-acceptor interaction parameter (CDA), and critical distance (R0) were also calculated. Next, the direct and indirect allowed transitions, the band tailing (B), and Urbach parameters (ΔE) were calculated. Then the shielding parameters, including the mass attenuation coefficient (MAC), the mean free path (MFP), and the equivalent atomic number (Zeq), etc., were articulated. Based on the above parameters, 1PrBLCZFB and 2PrBLCZFB glasses are suggested to be used for future solid-state orange-red laser, photonic devices, optical amplifier, and gamma ray shielding.

Judd-Ofelt analysis and visible luminescence of Sm3+: MCZBP glass for reddish-orange laser and multi-colour display applications

A new series of Sm3+ ions doped magnesium cadmium zinc borophosphate (Sm3+: MCZBP) glasses were prepared with melt quenching, and were characterized with X-ray diffraction, optical absorption spectra, excitation spectrum, emission spectra, and fluorescence decay curves. The increase of Sm3+ ions concentration increased the density (ρ), refractive index (n) and decreased the molar volume (Vm) of the glass. The non-metallic nature was identified from the metallization factor (M). The optical absorption spectra were used to understand the optical band gap (direct and indirect). The oscillator strength and Judd-Ofelt (JO) intensity parameters were determined from the optical absorption spectra and further used to evaluate the radiative properties of the Sm3+ ions doped glasses. The luminescence spectra showed the four emissions from transitions 4G5/2→6HJ (J = 5/2, 7/2, 9/2, and 11/2), corresponding to 562 nm (17793 cm−1), 597 nm (16750 cm−1), 644 nm (15527 cm−1) and 704 nm (14204 cm−1) upon exciting with 401 nm (24937 cm−1) wavelength, respectively. CIE chromaticity co-ordinates (x, y), the colour purity (CP), and the correlated colour temperature (CCT) values were calculated, showing that the emission colour fell in the reddish-orange region. The experimental lifetime (τexp), quantum efficiency (η), stimulated emission cross-section (σPE), gain bandwidth (σPE×Δλeff), and optical gain parameter (σPE×τexp) were articulated from the emission spectra of the glasses. The decay curves of 4G5/2 excited state exhibited non-exponential profile for all the present glasses. The efficient energy transfer between two Sm3+ ions through cross-relaxation was analysed with Inokuti-Hirayama (IH) model (S = 6). All the absorption and spectroscopic results revealed that 1SmMCZBP glass had a strong reddish-orange emission at 597 nm corresponding to 4G5/2 → 6H7/2 transition, and could be very promising material for laser and multi-colour display.

Development of test methodologies for experimental lifetime investigations of tidal turbines

As a regenerative energy source, tidal energy can significantly contribute to greenhouse gas reduction, even though the potentially achievable energy output is lower than that of wind or solar energy. The decisive advantage of tidal turbines lies in the simply and reliably predictable energy output. However, their commercial use has so far been impeded by the fact that on the one hand complex mechanical systems are required to convert energy of tidal currents and on the other hand multi-axial loading conditions caused by turbulent ocean currents act on the turbine. For this reason, field tests on prototypes are an essential part of the development strategy to ensure operational reliability. However, in-field tests do not allow for accelerated lifetime testing, so that test bench experiments are becoming an increasingly important alternative. Today, established procedures for testing the turbines main bearings and gearing system are already available, both for setting up the required test configuration and for determining the corresponding test loads. However, the use of advanced calculation methods, such as the finite element method for stress calculation, requires a deep understanding of the examined components and hinders the transfer of the approaches to other components.To simplify the process of test loads determination, a general methodology is presented, which relies exclusively on standardized empirical calculation rules. Doing this, fatigue equivalent loads can be determined for any component in a simple process. It was shown that the achieved reduction in complexity opens further potential for test acceleration, since several components can be tested simultaneously.

Suppression of background emission for efficient single-photon generation in micropillar cavities

We optimize the efficiency of a quantum-dot-based micropillar single-photon source by minimizing the spontaneous emission into unwanted background modes. We perform a numerical investigation of the background emission, where we identify a semi-periodic enhancement with the diameter. At these peaks of the background emission, the efficiency is reduced by ∼20%, and we show how this reduction can be avoided simply by choosing a diameter away from the peaks. Finally, we analyze the discrepancy between the Purcell factor estimated from experimental lifetime measurements and the true Purcell factor.

A proposed solution for the lifetime puzzle of the [formula omitted]Th+ isomer

With the example of the 229Th nucleus, which is the most likely candidate for the creation frequency standard of a future, the dynamics of the interplay and the relationship of various resonance conversion mechanisms is analyzed. As a result, a solution is proposed for the so-called thorium puzzle, which consisted of a contradiction between the experimental and theoretical lifetimes of Th+ ions. First, the solution demonstrates the dependence of the lifetime of the nuclear isomer on the ambient conditions. Second, it demonstrates the leveling role of the fragmentation of the single-electron levels, which makes the resonance amplification of the electron-nuclear interaction more likely. Both of these trends lead to a probable decrease of the theoretical lifetime towards agreement with experiment.

Concentration dependent neodymium doped oxy fluoroborate glasses for 1.08 μm laser applications

Different concentrations of neodymium-doped (Nd3+ ions) Oxy Fluoroborate (OFB) glasses were fabricated and systematically analyzed by employing spectroscopic techniques such as optical absorption, photoluminescence (PL) and PL decay spectral measurements to understand the NIR lasing potentialities. The information pertaining to absorption spectral features were subjected to Judd-Ofelt (J-O) analysis to understand the radiative properties such as transition probability (AR), radiative lifetime (τR) and branching ratios (βR) possessed by the as prepared Nd3+ ions doped OFB glasses. By correlating the radiative properties with the emission and PL decay spectral profiles, the emission cross-sections (σse) and quantum efficiency values are evaluated for the prominent fluorescent levels of Nd3+ ions in the as prepared glasses. Under 808 nm diode laser excitation, all the OFB glasses under investigation showcased two prominent NIR emissions at 1085 nm (4F3/2 → 4I11/2) and 1328 nm (4F3/2 → 4I13/2). The intensities of both the emission peaks escalates with increases in Nd3+ ions concentration up to 1 mol% and beyond decreases showcasing concentration quenching. The experimental lifetime values estimated from the single exponential PL decay profiles of 4F3/2 level are decreasing monotonously with increase in Nd3+ ions concentration in the as prepared OFB glasses. Relatively higher branching ratios, emission cross-sections and quantum efficiency values estimated for Nd3+ ions doped OFB glasses indicates the potential usage of the as prepared glasses for 1.08 μm laser applications.

Characterisation of Steel Components Fatigue Life Phenomenon Based on Magnetic Flux Leakage Parameters

The metal magnetic memory (MMM) method is highly effective in assessing the extent of early damage, such as fatigue crack in ferromagnetic components due to the existence of stress concentration zones (SCZs). However, there are limited studies on the relationship between the magnetic signal parameter in predicting the fatigue life of ferromagnetic components. With the advent of information relating to fatigue life, the risk of failure of a component can be reduced, if not avoided. Therefore, this study was conducted using the MMM method to establish a relationship between the magnetic signal parameters in the SCZ with fatigue characteristics in predicting the fatigue life of the specimen. A cyclic test was conducted on SAE 1045 steel specimens using a constant amplitude tension–compression stress with a stress ratio of −1. To investigate the effect of load value on the fatigue life of the specimens, seven percentage values of ultimate tensile strength (UTS) were used: 50%, 55%, 60%, 65%, 70%, 75%, and 80%. During the fatigue crack growth test, the MMM sensor was used to scan the magnetic signal data. Then, the data were analysed using the MMM Lifetime 2.0 software to obtain the fatigue life. Correlation graphs were plotted to determine the relationship between the MMM Lifetime 2.0 residual life and experimental residual life. The experimental results show that the distribution of magnetic signals was affected by the number of cycles and measurement line. As the number of cycles increased, the magnetic signal changes were more noticeable. For the measurement line, when the line was located near the crack initiation point, the magnetic signal distribution became clearer due to the presence of the SCZ. The evaluation of the maximum gradient, Kmax, variation also helped to assess the level of fatigue life based on the three stages of fatigue crack formation. Whereas, for the fatigue life assessment, the second measurement line (L2) and a contraction value of 0.7 were found to be suitable for predicting the fatigue life of specimens using MMM Lifetime 2.0 software. The experimental fatigue life and MMM Lifetime 2.0 fatigue life distribution of both parameters were in the two-factor range with the correlation coefficient, R2 of 0.9983. As such, the fatigue prediction results were acceptable. Accordingly, this study has demonstrated that the MMM method can be used to predict the remaining life of ferromagnetic components if the right parameters are used.

Stress rupture of fiber-reinforced ceramic-matrix composites subjected to different stochastic loading spectrums at intermediate temperatures

In this paper, stress rupture of fiber-reinforced ceramic-matrix composites (CMCs) subjected to different stochastic loading spectrums at intermediate temperatures (600 to 1000 °C) is investigated. Under stress rupture at stress level higher than the first matrix cracking stress, multiple damage mechanisms of matrix cracking, fiber/matrix interface debonding, interphase and fiber oxidation, and fiber fracture are considered to analyze evolution of composite strain. Four different stochastic loading spectrums are considered in the analysis of damage evolution and lifetime of fiber-reinforced CMCs under stress rupture loading. Relationships between stochastic loading stress, frequency, time, interface debonding and oxidation length, fiber failure probability, and stress rupture lifetime are established. Effects of stochastic loading stress and time, fiber volume, matrix crack spacing, interface debonding energy, interface shear stress, and temperature on composite strain, interface debonding and oxidation length, and the fiber failure probability versus time are analyzed. Experimental stress rupture strain and lifetime of SiC/SiC composite under constant stress and stochastic loading spectrums are predicted. When the stochastic loading stress, frequency, and temperature increase, the stress rupture lifetime and the time for the interface complete debonding and oxidation all decrease.

Unraveling the site-specific energy transfer driven tunable emission characteristics of Eu3+ & Tb3+ co-doped Ca10(PO4)6F2 phosphors.

In this study we have explored Ca10(PO4)6F2 as host to develop a variety of phosphor materials with tunable emission and lifetime characteristics based on Eu3+ and Tb3+ as co-dopant ions and the energy transfer process involved with them. The energy transfer from the excited state of Tb3+ ion to the 5D0 state of Eu3+ makes it possible to tune the colour characteristics from yellow to orange to red. Further, such energy transfer process is highly dependent on the concentration of Eu3+ and Tb3+ ions and their site-selective distribution among the two different Ca-sites (CaO9 and CaO6F) available. We have carried out DFT based theoretical calculation for both Eu3+ and Tb3+ ions in order to understand their distribution. It was observed that in cases of co-doped sample, Tb3+ ions prefer to occupy the Ca2 site in the CaO6F network while Eu3+ ions prefer Ca1 site in the CaO9 network. This distribution has significant impact on the lifetime values and the energy transfer process as observed in the experimental photoluminescence lifetime values. We have observed that for the 1st series of compounds, wherein the concentration Tb3+ ions are fixed, the energy transfer from Tb3+ ion at Ca2 site to Eu3+ ion at Ca1 site is dominating (Tb3+@Ca2 → Eu3+@Ca1). However, for the 2nd series of compounds, wherein the concentration Eu3+ ions are fixed, the energy transfer process was found to occur from the excited Tb3+ ion at Ca1 site to Eu3+ ions at both Ca1 and Ca2 (Tb3+@Ca1 → Eu3+@Ca1 and Tb3+@Ca1 → Eu3+@Ca2). This is the first reports of its kind on site-specific energy transfer driven colour tunable emission characteristics in Eu3+ and Tb3+ co-doped Ca10(PO4)6F2 phosphor and it will pave the way for the future development of effective colour tunable phosphor materials based on a single host and same co-dopant ions.

Numerical modeling of the low cycle fatigue: effect of manufacturing imperfections caused by machining process

The majority of mechanical components in nuclear power plants must be designed to withstand extreme cyclic loading conditions. In fact, when these components are subjected to low cycle fatigue, machining imperfections are considered one of the most significant factors limiting their service life. In the present work, using finite element analysis, a methodology has been suggested to predict the fatigue life of cylindrical parts made of 316 SS, at ambient temperature, under nominal strain amplitude ranging from ± 0.5 to ±1.2% with various surface roughness conditions. Two different multiaxial strain-life criteria have been considered to estimate the fatigue life, namely Brown-Miller and maximum shear strain. The comparison between the predicted and the experimental fatigue lifetimes has revealed that the adopted multiaxial strain life criteria can successfully estimate the fatigue life of 316 SS grade under uniaxial loading conditions. Furthermore, it has been found that the fatigue life decreases as the surface roughness average value increases, which indicates that surface regularities have a significant impact on low cycle fatigue life. Therefore, the proposed methodology is found to be capable of assessing the impact of surface roughness on the fatigue life of this specific steel in the low cycle fatigue regime.

Multiphoton light emission in barium stannate perovskites driven by oxygen vacancies, Eu3+ and La3+: accessing the role of defects and local structures.

Defect engineering in perovskites has been found to be the most efficient approach to manipulate their performance in ultraviolet-to-visible photon conversion. Under UV irradiation, BaSnO3 exhibited multicolor photoluminescence (MCPL) in the bluish white region. Its origin has not been well studied in the literature and has been probed in this work using synchrotron radiation, positron annihilation and density functional theory. To achieve desirable performance of doped BaSnO3 in optoelectronics, it is imperative to have correct information on the dopant local site, doping induced defect evolution and efficacy of host to dopant energy transfer (HDET). Extended X-ray absorption fine structure (EXAFS) showed that Eu3+ ions stabilize at both Ba2+ and Sn4+ sites consistent with the highly negative formation energy of around -6.26 eV. Eu3+ doping leads to an intense 5D0→7F1 orange emission and a feeble 5D0→7F2 red emission and an internal quantum yield (IQY) of ∼21% mediated by ET from the defect level of EuBa and EuSn sites to the valence band maximum (VBM). X-ray absorption near edge structure (XANES) ruled out any role of Sn2+ in the PL of BaSnO3 or Eu2+ in the PL of BaSnO3:Eu3+. Interestingly, when co-doped, Eu3+ stabilizes at Sn4+ sites whereas La3+ stabilizes at Ba2+ sites with a formation energy value of -6.44 eV. Based on the asymmetry ratio in emission spectra, it was found that La3+ ions lead to lowering of symmetry around Eu3+ due to increased vacancies and structural distortions, and also suppress the luminescence IQY. We have performed experimental positron annihilation lifetime spectroscopy (PALS) to probe the defects in BaSnO3 in pristine samples and on doping/co-doping. The positron lifetimes for saturation trapping of positrons in various kinds of defects envisaged in BaSnO3 and in the defect free system were calculated using the MIKA Doppler program. Such deep insight into the effect of local structures, dopant sites, defect evolution, ET, etc. on the optical properties of BaSnO3 is expected to provide very deep insight for material scientists into the fabrication of perovskite-based optoelectronic and light-emitting devices.

Pulsed Interleaved MINFLUX.

We introduce p-MINFLUX, a new implementation of the highly photon-efficient single-molecule localization method with a simplified experimental setup and additional fluorescence lifetime information. In contrast to the original MINFLUX implementation, p-MINFLUX uses interleaved laser pulses to deliver the doughnut-shaped excitation foci at a maximum repetition rate. Using both static and dynamic DNA origami model systems, we demonstrate the performance of p-MINFLUX for single-molecule localization nanoscopy and tracking, respectively. p-MINFLUX delivers 1-2 nm localization precision with 2000-1000 photon counts. In addition, p-MINFLUX gives access to the fluorescence lifetime enabling multiplexing and super-resolved lifetime imaging. p-MINFLUX should help to unlock the full potential of innovative single-molecule localization schemes.

A novel Er3+ ions doped zirconium magnesium borate glass with very high quantum efficiency for green laser and optical amplifier applications

A potential new series of Er3+ ions doped zirconium magnesium borate (ZMB) glasses have been prepared by conventional melt quenching method. Aperiodic nature of the glasses was confirmed by X-ray diffraction analysis. SEM image shows the nonappearance of any defined shape or structure which confirms the amorphous nature. The Refractive index of the glasses increases in the value from 1.611 to 1.671 with increase of Er3+ ion concentration. The optical absorption, excitation and emission spectra of the Er3+ doped glasses were recorded from ultraviolet (UV) to visible (Vis) and near infra-red (NIR) range with different equipment's. The oscillator strength and JO intensity parameter (Ω2, Ω4 and Ω6) were calculated from the absorption spectra. The photoluminescence spectra of the present glasses exhibit two emissions (2H11/2 → 4I15/2 and 4S3/2 → 4I15/2) bands in the visible region by exciting 491 nm and exhibit one emission (4I13/2 → 4I15/2) in the NIR region with the 980 nm as an excitation source. The experimental lifetime (τexp), FWHM, figure of merit (σPE × τexp), gain bandwidth (σPE × Δλeff) and stimulated emission cross-section (σPE) values have been calculated for all the present glasses for visible and NIR emission transition. The decay spectra measured for 4I13/2 → 4I15/2 transition shows single exponentials for all Er3+ ion concentrations of the glasses. CIE 1931 diagram shows the exact emission colour (green) of the prepared glasses. Correlated colour temperature points show along with the block body curve line and can be used for cold lighting purposes. From the all the results, it is observed that, 1ErZMB glass is more potential candidate for green laser, optical amplifier and designing of photonic devices.

Spectroscopic properties of Er:BZMT ceramics for laser emission

We report on the characterization and analysis of the spectroscopic properties of an Er3+-doped Ba(Zr,Mg,Ta)O3 (Er:BZMT) transparent ceramic showing a disordered perovskite structure. The Judd-Ofelt model was applied to estimate the radiative lifetimes and branching ratios of the 1.5 and 3 µm emission transitions, which are potential for laser operation. The experimental fluorescence lifetimes of the transitions of 4I13/2 → 4I15/2 and 4I11/2 → 4I13/2 were recorded to calculate the radiative quantum efficiencies. According to the analysis, significant non-radiative relaxation processes from the 4I11/2 multiplets should exist in the Er:BZMT system, which makes this material more suitable for laser operation at 1.6 µm. Finally, the gain cross-section for the potential 1.6 µm laser emission was calculated, showing a broad tuning range from less than 1.6 µm to around 1.7 µm. This result also indicates that femtosecond level laser pulses are possible using Er:BZMT as laser gain medium.

Effect of Temperature on Luminescence of LiNbO3 Crystals Single-Doped with Sm3+, Tb3+, or Dy3+ Ions

Crystals of LiNbO3 single-doped with Sm3+, Tb3+, or Dy3+ and crystal of LiTaO3 single-doped with Tb3+ were grown by the Czochralski method. Luminescence spectra and decay curves for LiNbO3 samples containing Sm3+ or Dy3+ ions were recorded at different temperatures between 295 and 775 K, whereas those for samples containing Tb3+ ions were recorded at different temperatures between 10 and 300 K. Optical absorption spectra at different temperatures were recorded within the UV-blue region relevant to optical pumping of the samples. It was found that the effect of temperature on experimental luminescence lifetimes consists of the initial temperature-independent stage followed by a steep decrease with the onset at about 700, 600, and 150 K for Sm3+, Dy3+, and Tb3+ ions, respectively. Additionally, comparison of temperature impact on luminescence properties of LiNbO3:Tb3+ and LiTaO3:Tb3+ crystals has been adequately described. Experimental results were interpreted in terms of temperature-dependent charge transfer (CT) transitions within the modified Temperature—Dependent Charge Transfer phenomenological model (TDCT). Disparity of the onset temperatures and their sequence were explained based on the location of familiar zigzag curves connecting the ground state levels of rare earth ions with respect to the band-gap of the host. It was concluded also that LiNbO3:Sm3+ is suitable as an optical sensor within the 500–750 K temperature region whereas LiNbO3:Dy3+ offers the highest sensitivity at lower temperatures between 300 and 400 K.

Near-infrared Opacity of Late M Dwarfs and Hot Jupiters: The E3Π–X3Δ Transition of TiO

Abstract The TiO E 3Π–X 3Δ transition is an important opacity source in the near-infrared spectra of late M dwarfs. The 0–0 band of the 48Ti16O E 3Π–X 3Δ electronic transition has been reanalyzed using a recently published set of high-resolution, high temperature absorption cross sections. The analysis has been extended to higher J values and an improved set of spectroscopic constants were determined. Calculated high-precision line lists for the 0–0 and 0–1 bands are provided with line strengths based on a previously measured experimental lifetime.

A lifetime assessment and prediction method for large area solder joints

Mechanical bending fatigue experiments were conducted on large area Pb-rich and SnSb-based model solder joints consisting of Cu-strip/solder/DCB substrates. Experimental lifetime curves in the range between 105 and 108 loading cycles at room and elevated temperature showed an improved fatigue resistance for SnSb alloys. Crack length as a function of loading cycles (da/dN) was determined for selected samples to study the cyclic degradation behaviour of the solder layer. Crack initiation and propagation in the joints was modelled on the basis of a damage accumulation rule considering the strain rate and temperature dependency of the solder alloy. Application of the FEM model to large area solder joints allowed calculation of the incremental advancement of the crack front, determination of the crack growth rate (da/dN) and prediction of lifetime under a given loading condition.