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Miniaturized spectrometers that are absent of bulky dispersive optical elements have received more and more attention. However, most of these advancements have been demonstrated in the visible spectrum. Among the various near‐infrared (NIR) absorbers, organic donor–acceptor blends exhibit a distinctive red‐shifted intermolecular charge‐transfer (CT) state absorption, allowing for the detection of NIR photons below the distinct molecular band edge. Nevertheless, the sub‐bandgap absorption cross‐section has been rather limited. In this study, this challenge is addressed by integrating a metal–dielectric (M–D) microcavity into a prototype (PM6:Y6) model system, with a band‐edge positioned at 869 nm. As a result, an amplified narrowband detection, demonstrating an external quantum efficiency of ≈26% at 905 nm is achieved. Furthermore, the manipulation of the cavity lengths enables easy fine‐tuning of the narrowband spectral response within the 850–960 nm range. Leveraging a spectrum reconstruction algorithm, a spectral detector with 10 nm resolution under a zero bias, validating the potential of utilizing sub‐bandgap CT state absorption for efficient narrowband detectors and micro‐spectrometers is obtained. [ABSTRACT FROM AUTHOR]

Abstract There has been a rapidly growing demand for low-cost, integrated single-shot spectrometers to be embedded in portable intelligent devices. Even though significant progress has been made in this area, two major problems are still remaining, namely the high temperature sensitivity and poor bandwidth-resolution ratio (BRR) that can’t meet the requirement of most applications. In this work, we present an integrated single-shot spectrometer relying on a silicon photonic circuit that has a footprint less than 3mm2, but could achieve broad operation bandwidth about 100 nm and high resolution up to 0.1 nm (with a BRR ~ 1000). Moreover, for the first time, we demonstrate an integrated spectrometer that could operate within a wide temperature range (between 10 and 70 degrees Celsius) without additional power consumption for temperature management.

There has been a rapidly growing demand for low-cost, integrated single-shot spectrometers to be embedded in portable intelligent devices. Even though significant progress has been made in this area, two major problems are still remaining, namely the high temperature sensitivity and poor bandwidth-resolution ratio (BRR) that can't meet the requirement of most applications. In this work, we present an integrated single-shot spectrometer relying on a silicon photonic circuit that has a footprint less than 3mm2, but could achieve broad operation bandwidth about 100 nm and high resolution up to 0.1 nm (with a BRR ~ 1000). Moreover, for the first time, we demonstrate an integrated spectrometer that could operate within a wide temperature range (between 10 and 70 degrees Celsius) without additional power consumption for temperature management. [ABSTRACT FROM AUTHOR]

The essential component of modern radiation therapy is the application of steep dose gradients during patient treatment in order to maximize the radiation dose to the target volume and protect neighboring heathy tissues. However, volumetric dose distribution in an irradiated target is still a bottleneck of dose verification in modern radiotherapy. Dose gels are almost the only known dosimetry tool which allows for the evaluation of dose distribution in the irradiated volume due to gel's polymerization upon irradiation. The accuracy of dose gel dosimetry has its own obstacle, which is related to the continuation of the gel's polymerization after the radiation treatment procedure is finished. In this article, a method to monitor the polymerization dynamics of dose gels in real-time is proposed using a modified optical spectrometry system. Using the proposed method, the changes of the optical characteristics of irradiated nMAG dose gels in situ were assessed. The investigation revealed that the detectable polymerization in dose gel proceeds up to 6 h after irradiation. This time is significantly shorter compared with a commonly recommended 24 h waiting time allocated for polymer gel to settle. It was also found that dose rate significantly influences the temporal response of the nMAG dosimeter. By increasing the irradiation dose rate by a factor of 2, the time needed for the polymerization process to settle was increased by 22%. Identification of the gel's post-irradiation polymerization time interval and its dependence on irradiation parameters will contribute to more accurate dose verification using dose gel dosimetry. [ABSTRACT FROM AUTHOR]

The symmetrical quasi-classical approach for propagation of a many degree of freedom density matrix is explored in the context of computing linear spectra. Calculations on a simple two state model for which exact results are available suggest that the approach gives a qualitative description of peak positions, relative amplitudes, and line broadening. Short time details in the computed dipole autocorrelation function result in exaggerated tails in the spectrum. [ABSTRACT FROM AUTHOR]

Unlike the single grating Czerny–Turner configuration spectrometers, a super-high spectral resolution optical spectrometer with zero coma aberration is first experimentally demonstrated by using a compound integrated diffraction grating module consisting of 44 high dispersion sub-gratings and a two-dimensional backside-illuminated charge-coupled device array photodetector. The demonstrated super-high resolution spectrometer gives 0.005 nm (5 pm) spectral resolution in ultra-violet range and 0.01 nm spectral resolution in the visible range, as well as a uniform efficiency of diffraction in a broad 200 nm to 1000 nm wavelength region. Our new zero-off-axis spectrometer configuration has the unique merit that enables it to be used for a wide range of spectral sensing and measurement applications. [ABSTRACT FROM AUTHOR]

In the description of the interaction between electrons beyond the classical Hartree picture, bare exchange often yields a leading contribution. Here we discuss its effect on optical spectra of solids, comparing three different frameworks: time-dependent Hartree-Fock, a recently introduced combined density-functional and Green’s function approaches applied to the bare exchange self-energy, and time-dependent exact exchange within time-dependent density-functional theory (TD-EXX). We show that these three approximations give rise to identical excitonic effects in solids; these effects are drastically overestimated for semiconductors. They are partially compensated by the usual overestimation of the quasiparticle band gap within Hartree-Fock. The physics that lacks in these approaches can be formulated as screening. We show that the introduction of screening in TD-EXX indeed leads to a formulation that is equivalent to previously proposed functionals derived from many-body perturbation theory. It can be simulated by reducing the long-range part of the Coulomb interaction: this produces absorption spectra of semiconductors in good agreement with experiment. [ABSTRACT FROM AUTHOR]

We develop a linear response theory of solvation of ionic and dipolar solutes in anisotropic, axially symmetric polar solvents. The theory is applied to solvation in polar nematic liquid crystals. The formal theory constructs the solvation response function from projections of the solvent dipolar susceptibility on rotational invariants. These projections are obtained from Monte Carlo simulations of a fluid of dipolar spherocylinders which can exist both in the isotropic and nematic phases. Based on the properties of the solvent susceptibility from simulations and the formal solution, we have obtained a formula for the solvation free energy which incorporates the experimentally available properties of nematics and the length of correlation between the dipoles in the liquid crystal. The theory provides a quantitative framework for analyzing the steady-state and time-resolved optical spectra and makes several experimentally testable predictions. The equilibrium free energy of solvation, anisotropic in the nematic phase, is given by a quadratic function of cosine of the angle between the solute dipole and the solvent nematic director. The sign of solvation anisotropy is determined by the sign of dielectric anisotropy of the solvent: solvation anisotropy is negative in solvents with positive dielectric anisotropy and vice versa. The solvation free energy is discontinuous at the point of isotropic-nematic phase transition. The amplitude of this discontinuity is strongly affected by the size of the solute becoming less pronounced for larger solutes. The discontinuity itself and the magnitude of the splitting of the solvation free energy in the nematic phase are mostly affected by microscopic dipolar correlations in the nematic solvent. Illustrative calculations are presented for the equilibrium Stokes shift and the Stokes shift time correlation function of coumarin-153 in 4-n-pentyl-4′-cyanobiphenyl and 4,4-n-heptyl-cyanopiphenyl solvents as a function of temperature in both the nematic and isotropic phases. [ABSTRACT FROM AUTHOR]

Composition fluctuations in GaN:Mg have been investigated by optical transmission spectroscopy, near-field scanning optical microscopy (NSOM), and scanning Kelvin probe microscopy (SKPM). An Urbach tail is observed in the optical transmission spectrum of heavily Mg-doped GaN, with the magnitude of Urbach energy increasing with increasing compositional/potential fluctuations. From the relationship between the Urbach energy and the potential fluctuation magnitude, the spatial size of the compositional fluctuations in GaN:Mg (with the average Mg concentration of ∼4×1019 cm-3) is calculated to be 220 nm. The nanoscale compositional fluctuations are determined by NSOM and SKPM. A spatial variation of the transmission mode NSOM intensity is observed with a characteristic wavelength of ∼300 nm, which is attributed to the inhomogeneous distribution of Mg. The normalized root-mean-square (rms) fluctuation of the transmission mode NSOM intensity for heavily Mg-doped GaN is a factor of 5 greater than that for undoped GaN. Similar microstructure patterns are observed in the NSOM and surface potential images of GaN:Mg as probed by SKPM. The variation of local surface potential (on the order of 100 mV) is attributed to the same compositional fluctuations of Mg, which changes the local surface work function. The local Mg concentrations are calculated from the SKPM image. For GaN:Mg with the Mg concentration of 4×1019 cm-3, a rms value of 5.4×1019 cm-3 of the compositional fluctuations has been observed. [ABSTRACT FROM AUTHOR]

Femtosecond laser ablation of Ti, Zr, and Hf has been investigated by means of in situ plasma diagnostics. Fast imaging was used to characterize the plasma plume expansion on a nanosecond time scale. In addition, time- and space-resolved optical emission spectroscopy was employed to determine the plume composition and the characteristic expansion velocities of plasma species. It is shown that two plume components with different expansion velocities are generated by the interaction of ultrashort laser pulses with metals. The composition and the expansion behavior of the two components have been analyzed as a function of laser fluence and target material. The results are discussed in terms of mechanisms responsible for ablation by ultrashort laser pulses. [ABSTRACT FROM AUTHOR]

Polarized optical spectra of quaterthiophene single crystals are reported over a wide spectral range for different planes and angles of incidence corresponding to either transverse or mixed longitudinal/transverse wave propagation. From the absorbance and reflectance spectra the corresponding absorption coefficients are deduced. In the region of the first molecular transition, polarized exciton states of Frenkel origin are found to be responsible for a strong optical anisotropy and for the modification of the state of polarization during light propagation in the crystal. Transmission measurements with crossed polarizer and analyzer allow to clearly identify Frenkel replica of the principal transition. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The influence of solvent dynamics on optical spectra is often described by a stochastic model which assumes exponential relaxation of the time-correlation function for solvent-induced frequency fluctuations. In contrast, theory and experiment suggest that the initial (subpicosecond) phase of solvent relaxation, resulting from inertial motion of the solvent, is a Gaussian function of time. In this work, we employ numerical and analytical calculations to compare the predicted absorption line shapes and the derived solvent reorganization energies obtained from exponential (Brownian oscillator) versus Gaussian (inertial) solvent dynamics. Both models predict motional narrowing as the ratio κ=Λ/Δ is increased, where Λ and Δ are the frequency and variance, respectively, of the solvent-induced frequency fluctuations. However, the motional narrowing limit is achieved at lower values of κ for the Brownian oscillator model compared to the inertial model. For a given line shape, the derived value of the solvent reorganization energy λ[sub solv] is only weakly dependent on the solvent relaxation model employed, though different solvent parameters Λ and Δ are obtained. The two models are applied to the analysis of the temperature-dependent absorption spectrum of β-carotene in isopentane and CS[sub 2]. The derived values of λ[sub solv] using the Gaussian model are found to be in better agreement with the high temperature limit of Δ[sup 2]/2k[sub B]T than are the values obtained using the Brownian oscillator model. In either approach, the solvent reorganization energy is found to increase slightly with temperature as a result of an increase in the variance Δ of the solvent-induced frequency fluctuations. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We have used a multitude of linear and nonlinear cw optical spectroscopies to study the optical properties of water precursor poly(p-phenylene vinylene) (PPV) thin films. These spectroscopies include absorption, photoluminescence, photoinduced absorption and their respective optically detected magnetic resonance, and electroabsorption spectroscopy. We have studied singlet and triplet excitons, polarons, and laser action in PPV films. We found that the lowest-lying absorption band is excitonic in origin. It consists of two absorption components due to a bimodal distribution of the polymer chain conjugation lengths. Electroabsorption spectroscopy unambiguously shows the positions of the lowest-lying odd parity exciton 1B[sub u] at 2.59 eV and two of the higher-lying even-parity excitons, namely, mA[sub g] at 3.4 eV and kA[sub g] at 3.7 eV. From these exciton energies we obtained a lower bound for the exciton binding energy in PPV, E[sub b](min)=E(mA[sub g])-E(1B[sub u])=0.8 eV. The quantum efficiency spectrum for triplet exciton photogeneration consists of two contributions; the intersystem crossing and, at higher energies, singlet fission. From the onset of the singlet fission process at E[sub SF]=2E[sub T], we could estimate the energy of the lowest-lying triplet exciton, 1 [sup 3]B[sub u], at 1.55 eV, with a singlet–triplet splitting as large as 0.9 eV. From photoinduced absorption spectroscopy we measured the triplet–triplet transition, T→T[sup *], to be 1.45 eV. The quantum efficiency spectrum for polaron photogeneration also consists of two contributions: one extrinsic and the other intrinsic. The latter shows a monotonically increasing function of energy with an energy onset at 3.3 eV. The intrinsic photogeneration process is analyzed with a model of free-electron–hole pair photogeneration, which separate more effectively at higher energy. The carrier generation quantum yield at 3.65 eV is estimated to be 0.5%. The quantum... [ABSTRACT FROM AUTHOR]

Studies self-assembled nanocrystalline dots of CdS grown within ZnSe host by steady state and transient optical spectroscopies. Presence of an unusually low density of the dots in the material system; Identification of the excitation transfer of excitons from the host; Efficacy of excitonic energy transfer from the ZnSe host to the dots; Possibility of a large effective capture cross section.

Optical spectrometers and sensors have gained enormous importance in metrology and information technology, frequently involving the question of size, resolution, sensitivity, spectral range, efficiency, reliability, and cost. Nanomaterials and nanotechnological fabrication technologies have huge potential to enable an optimization between these demands, which in some cases are counteracting each other. This paper focuses on the visible and near infrared spectral range and on five types of optical sensors (optical spectrometers): classical grating-based miniaturized spectrometers, arrayed waveguide grating devices, static Fabry–Pérot (FP) filter arrays on sensor arrays, tunable microelectromechanical systems (MEMS) FP filter arrays, and MEMS tunable photonic crystal filters. The comparison between this selection of concepts concentrates on (i) linewidth and resolution, (ii) required space for a selected spectral range, (iii) efficiency in using available light, and (iv) potential of nanoimprint for cost reduction and yield increase. The main part of this review deals with our own results in the field of static FP filter arrays and MEMS tunable FP filter arrays. In addition, technology for efficiency boosting to get more of the available light is demonstrated.

Examines the calculation of optical spectra in liquid methanol using molecular dynamics and the chemical potential equalization method (CPE). Application of the CPE technique as analytic tool for computing the infrared (IR) and Raman spectra of liquid methanol starting from classical trajectories generated by a conventional potential; CPE principle.

Analyzes the manifestations of the Jahn-Teller effect on the optical spectroscopy of the Ag[sup +] ion in sodium fluoride (NaF). Details on the growth of NaF crystals containing Ag[sup +] ions isolated from each other using one- and two-photon spectroscopy; Comparison of Cu[sup +] and Ag[sup +] in NaF to better understand experimental parameters.

Presents information on a study on the spectra of silicon. Researches on the optical data of silicon at elevated temperature; Methodology used in conducting the study; Results.

Neutron diffraction and spectroscopy offer unique insight into structures and properties of solids and molecular materials. All neutron instruments located at the various neutron sources are distinct, even if their designs are based on similar principles, and thus, they are usually less familiar to the community than commercial X‐ray diffractometers and optical spectrometers. Major neutron instruments in the USA, which are open to scientists around the world, and examples of their use in coordination chemistry research are presented here, along with a list of similar instruments at main neutron facilities in other countries. The reader may easily and quickly find from this minireview an appropriate neutron instrument for research. The instruments include single‐crystal and powder diffractometers to determine structures, inelastic neutron scattering (INS) spectrometers to probe magnetic and vibrational excitations, and quasielastic neutron scattering (QENS) spectrometers to study molecular dynamics such as methyl rotation on ligands. Key and unique features of the diffraction and neutron spectroscopy that are relevant to inorganic chemistry are reviewed. Major instruments in the USA for (1) single‐crystal and powder neutron diffraction and (2) inelastic neutron scattering (INS) and quasielastic neutron scattering (QENS) spectroscopy are presented with examples of their use in coordination chemistry. Similar instruments at main neutron facilities in other countries are listed for the reader to find a suitable neutron instrument for research. [ABSTRACT FROM AUTHOR]

An automatic flow-through dynamic extraction method is proposed for the first time for in vitro exploration, with high temporal resolution, of the transit of the chyme from the gastric to the duodenal compartment using the Versantvoort's fed-state physiologically relevant extraction test. The flow manifold was coupled on-line to an inductively coupled plasma optical emission spectrometer (ICP OES) for real-time elucidation of the bioaccessible elemental fraction of micronutrients (viz., Cu, Fe and Mn) in food commodities across the gastrointestinal tract. The simulated intestinal and bile biofluid (added to the gastric phase) was successively pumped at 1.0 mL min −1 through a large-bore column (maintained at 37.0 ± 2.0 °C) initially loaded with a weighed amount of linseed (250 mg) using a PVDF filter membrane (5.0 μm pore size) for retaining of the solid sample and in-line filtration of the extracts. The lack of bias (trueness) of the on-line gastrointestinal extraction method coupled to ICP OES was confirmed using mass balance validation following microwave assisted digestion of the residual (non-bioaccessible) elemental fraction. Mass balance validation yielded absolute recoveries spanning from 79 to 121% for the overall analytes and samples. On-line dynamic extraction was critically appraised against batch counterparts for both gastric and gastrointestinal compartments. Due to the lack of consensus in the literature regarding the agitation method for batch oral bioaccessibility testing, several extraction approaches (viz., magnetic stirring, end-over-end rotation and orbital shaking) were evaluated. Improved gastric extractability of Fe along with bioaccessible data comparable to the dynamic counterpart based on the continuous displacement of the extraction equilibrium was obtained with batchwise magnetic stirring, which is deemed most appropriate for ascertaining worst-case/maximum bioaccessibility scenarios. [ABSTRACT FROM AUTHOR]

Presents a study which described a surface-laser light scattering spectrometer that uses optical heterodyne detection to measure the temporal behavior of the thermally generated capillary waves at a fluid/fluid interface. Details of instrumentation; Data analysis; Experimental results.

Presents a technique for the optical spectroscopy of adsorbed molecules. Cause of the Davydov splitting; Structure of the tetracene molecule; Method used to study tetracene molecule in the as-deposited state.

Quantum chemical calculations based on density functional theory have been performed on ruthenocene. Excellent agreement is obtained with ground- and excited-state properties derived from optical spectroscopy. In particular, the energies of the first d–d excitations, the unusually large Stokes shift, the structural expansion of Ru(cp)2 and the substantial reduction of the Ru-cp force constant in the first triplet excited state are almost quantitatively reproduced. The lowest-energy excitation is found to have substantial charge transfer character. [ABSTRACT FROM AUTHOR]

The optical spectra of actinide ions in the compound AnCl3 and doped into single-crystal LaCl3 were interpreted in terms of transitions within 5fN configurations. Energy-level calculations were carried out using an effective-operator Hamiltonian, the parameters of which were determined by fitting experimental data. Atomic and crystal-field matrices were diagonalized simultaneously assuming an approximate D3h site symmetry. Spectroscopic data were taken from the literature but in most cases supplemented by unpublished measurements in absorption and in fluorescence. Data for each ion were analyzed independently, then the model parameters were intercompared and in many cases adjusted such that in the final fitting process the principal interactions showed uniform trends in parameter values with increasing atomic number. Consistent with analyses of the spectra of lanthanide ions in both LaCl3 and LaF3, abrupt changes in magnitude of certain crystal-field parameters were found near the center of the 5fN series. This resulted in two groups of parameter values, but with consistent trends for both halves of the series, and generally very good agreement between observed and computed energies. A new energy-level chart based on computed crystal-field level energies for each trivalent actinide ion has been prepared. [ABSTRACT FROM AUTHOR]

The temperature-dependent optical spectra of the major insulating forms of polyaniline—the fully reduced leucoemeraldine base, half-oxidized emeraldine base (EB), and fully oxidized pernigraniline base (PNB)—and of two oligomeric model compounds for polyaniline are reported. All three forms of the polymer possess a ∼3.8 eV optical absorption assigned to a transition from the valence band to a narrow π* conduction band; in all cases this transition shifts to higher energy and weakens with increasing temperature, T. The oxidized forms also exhibit transitions at ∼2 eV; in EB, this absorption feature has previously been assigned to a ‘‘molecular exciton’’ and is found to increase in energy with increasing T. In PNB, the observed ∼2.3 eV transition is correlated with the expectation of a Peierls dimerization gap in this half-filled band system; in contrast to the ∼2 eV transition in EB, this optical transition energy decreases with increasing T in PNB. These observations are for the most part understood by a simple model which accounts for the steric repulsion between the constituent phenyl rings of the polymer chain. The dependence of the steric potential on ring angle is anharmonic, giving rise to thermal expansion of the average phenyl ring-torsion angles and a concomitant reduction in the bandwidth and average energy of the valence band; the observed thermochromic behavior is generally consistent with these changes in electronic structure. The potential role of other conformational changes—rod-to-coil transitions, order–disorder transitions, bond-length order changes, and structural isomerizations—is discussed. [ABSTRACT FROM AUTHOR]

Vibrationally resolved optical spectra, fluorescence decay times, and fluorescence quantum yields have been measured for all-trans diphenyloctatetraene and all-trans diphenyloctatetraene substituted in the para position(s) of the phenyl ring(s) with an electron donor (MeO) or (and) and electron acceptor (CN). The electronic excitation energies, S0–S1 and S0–S2 transition dipoles and vibrational properties of the spectra provide a detailed picture of the effects of donor–acceptor substitution on the S0, S1, and S2 states. The electronic excitation energies are well fit by a simple parametrized quantum-mechanical model for polyene electronic structure which is used to estimate substituent-induced shifts in π-electron density in the S0, S1, and S2 states. [ABSTRACT FROM AUTHOR]

An approximate solution technique for computing spectra of many-body molecular systems is proposed. We focus for concreteness on 0 K electronic absorption and emission spectra. From a time-domain perspective, it is necessary to propagate a well-defined initial Schrödinger wave packet on a specified potential energy surface in order to extract such spectra. In order to perform this task for systems with many degrees of freedom, we investigate the utility of a time-dependent Hartree factorization, in which the wave packet for the complete system is variationally factorized into a product of wave packets of smaller dimensionality. This method is shown to be both flexible and reliable for prototypical model systems associated with the physical problem of impurity spectra in host crystals. Successful application is made to a recently measured emission spectrum of I2 embedded in an argon matrix. [ABSTRACT FROM AUTHOR]

The optical spectra of the lanthanides doped into single crystal LaF3 have been interpreted in terms of transitions within 4f N configurations. Energy matrices combining free-ion terms with a crystal field for an approximate model which assumes C2v instead of the actual C2 site symmetry were diagonalized. Excellent correlations were obtained between experimental transition energies and the computed level structures. We also report the results of previously unpublished experimental spectroscopic investigations of Nd3+ and Sm3+:LaF3, as well as predicted energy levels for Pm3+:LaF3. The spectroscopic data for each ion were independently interpreted using an effective-operator model, then the model parameters were intercompared. Systematic trends have been identified, and a comprehensive energy level diagram is presented. [ABSTRACT FROM AUTHOR]

Provides information on an experimental investigating the interband optical spectra of the semiconducting beta phase of iron disilicide (beta-FeSi2) in the energy range from 0.5 to 5.0 eV. Methodology used to conduct the experiment; Results of the experiment; Discussion on the results.

Investigates the structure of optical phase change memory alloy, silver-vanadium-indium-antimony-tellurium (AVIST), by using optical reflectivity change, Raman spectroscopy and electron diffraction. Study of Sb, AgSb, AgSbTe and AgInTe films; Reversal of relative intensities for the AVIST films; Indication that the AgSbTe2 crystalline phase dominates.

Studies the origin of picosecond-pulse-induced, degenerate four-wave-mixing signals in KTN crystals. Details on the experiment; Optical spectra of KTN crystals; Information on the degenerate four-wave-mixing measurements.

Optical properties of new polydiacetylene (PDA) crystals substituted with fluorobenzene derivatives have been investigated by reflectance, Raman, and electroreflectance (ER) measurements. The results indicate that these fluorobenzene-substituted PDAs have an intermediate optical character between those of the acetylene-type and butatriene-type PDA chains. One of these PDA crystals, DFMDP, has been found to show an exceptionally high crystalline quality, which has enabled us to make a detailed spectroscopic study. ER studies on this DFMDP crystal have revealed the charge–transfer(CT)-type exciton lying at ∼2.7 eV on the higher-energy side of the lowest 1Bu exciton at ∼2.2 eV. On the basis of experimental results, it is conjectured that two-photon resonance with the CT exciton plays a major role in the third-order nonlinear optical process in PDA chains. [ABSTRACT FROM AUTHOR]

The temperature dependences of the fluorescence intensities and lifetimes of Mn2SiO4 and the results of time-resolved spectroscopy measurements on this material are reported. A model is developed to explain the results in terms of thermally activated migration of Mn2+ excitons terminating on deep trapping centers. Fiber growth techniques are shown to decrease the concentration of fluorescence quenching centers in this material, and dilution with Mg or Ca ions is found to decrease the efficiency of the quenching process. Four-wave mixing results suggest the presence of laser-induced photoionization processes in these crystals. [ABSTRACT FROM AUTHOR]

Hα spectral line (6563 Å) profiles of eight northern H II regions in our galaxy (Sh2-25, Sh2-131, Sh2-237, IC 434, IC 1318, NGC 1982, NGC 6543, and NGC 6611) have been obtained using the Dual Etalon Fabry-Pérot Optical spectrometer (DEFPOS) with a 4' field of view, located at the coudé focus of the 150 cm RTT150 telescope at the TÜBİTAK National Observatory (TUG, Antalya, Turkey). Observations were carried out during the nights of 25{27 December 2015 and 6-7 June 2017 with different long exposure times ranging from 900 s to 3600 s. These spectra provide information about the local standard of rest (LSR) velocities, the full width at half maximum (FWHM), and densities of the sources. The LSR velocities and the FWHM of the Hα emission lines were found to be in the range of {50.31 km/s to 27.57 km/s and 34.88 km/s to 44.54 km/s (mean FWHM: 37.19 km/s), respectively. The NGC 6543 (Cat's Eye Nebula) is the faintest one (75.06 R), while the NGC 1982 H II region is brightest source (38,477.3 R). The LSR velocity and the FWHM results of the DEFPOS/RTT150 system were compared with the data by several authors given in the literature and the results of DEFPOS data were found to be in good agreement with data given in the literature. Since there is not enough information on LSR velocities and intensities of such galactic sources with low angular size in the literature, we believe that this spectrometer will provide a powerful tool for the study of diffuse ionized gas and these new results may have significant contributions to the literature. In the future, we are planning to prepare Hα maps with the 4' field of view of some diffuse ionized emission sources selected from VTSS and WHAM Hα maps with large fields of view. [ABSTRACT FROM AUTHOR]

Utilizing its integrated camera, smartphone transforms to a burgeoning spectrometer which is promising for mHealth. However, this type of device suffers from the nonlinear sensitivity of camera which result in the imprecision of spectra. Here, we report a smartphone spectrometer with special designed calibration method to improve the spectral accuracy. Both wavelength calibration and intensity correction are adopted to eliminate the influence of nonlinear sensitivity from CMOS camera. The calibrated smartphone spectrometer is tested via comparing the fluorescence and absorption spectra of Rhodamine B with a standard commercial spectrometer. Meanwhile, the feasibility of this device in mHealth application is demonstrated via quantitative detection of creatinine. We argue that the high spectral accuracy and multimode-supporting ability enable the proposed smartphone spectrometer a powerful tool for mHealth with time and cost saving. [ABSTRACT FROM AUTHOR]

Imaging spectrometer obtains or indirectly obtains the spectral information of the ground surface feature while obtaining the target image, which makes the imaging spectroscopy has a prominent advantage in fine characterization of terrain features, and is of great significance for the study of geoscience and other related disciplines. Since the interference data obtained by interferometric imaging spectrometer is intermediate data, which must be reconstructed to achieve the high quality spectral data and finally used by users. The difficulty to restrict the application of interferometric imaging spectroscopy is to reconstruct the spectrum accurately. Based on the original image acquired by Large Aperture Static Imaging Spectrometer as the input, this experiment selected the pixel that is identified as crop by artificial recognition, extract and preprocess the interferogram to recovery the corresponding spectrum of this pixel. The result shows that the restructured spectrum formed a small crest near the wavelength of 0.55ìm with obvious troughs on both sides. The relative reflection intensity of the restructured spectrum rises abruptly at the wavelength around 0.7ìm, forming a steep slope. All these characteristics are similar with the spectral reflection curve of healthy green plants. It can be concluded that the experimental result is consistent with the visual interpretation results, thus validating the effectiveness of the scheme for interferometric imaging spectrum reconstruction proposed in this paper. [ABSTRACT FROM AUTHOR]

Today's reality is connected with mitigation of threats from the new chemical and biological warfare agents. A novel investigation of cold plasmas in contact with liquids presented in this paper demonstrated that the chemically reactive environment produced by atmospheric pressure plasma jet (APPJ) is potentially capable of rapid destruction of chemical warfare agents in a broad spectrum. The decontamination of three different chemical warfare agent surrogates dissolved in liquid is investigated by using an easily transportable APPJ. The jet is powered by a kHz signal source connected to a low-voltage DC source and with He as working gas. The detailed investigation of electrical properties is performed for various plasmas at different distances from the sample. The measurements of plasma properties in situ are supported by the optical spectrometry measurements, whereas the high performance liquid chromatography measurements before and after the treatment of aqueous solutions of Malathion, Fenitrothion and Dimethyl Methylphosphonate. These solutions are used to evaluate destruction and its efficiency for specific neural agent simulants. The particular removal rates are found to be from 56% up to 96% during 10 min treatment. The data obtained provide basis to evaluate APPJ's efficiency at different operating conditions. The presented results are promising and could be improved with different operating conditions and optimization of the decontamination process. Graphical abstract: [ABSTRACT FROM AUTHOR]