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2‐(3,6‐Bis(4‐methoxyphenyl)‐2,2,5,5‐tetramethyl‐4‐oxo‐4,5‐dihydropentalen‐1(2H)‐ylidene)malononitrile (DPM‐An) and 2,2′‐(3,6‐bis(4‐methoxyphenyl)‐2,2,5,5‐tetramethyl‐2,5‐dihydropentalene‐1,4‐diylidene)dimalononitrile (DPD‐An), both bearing the 2,5‐dihydropentalene core and intramolecular electron donor–acceptor moieties, were prepared and subjected to photophysical studies. The absorption spectra of DPM‐An and DPD‐An in CH2Cl2 at room temperature contain maxima at similar wavelengths of 406 and 409 nm, respectively. These substances do not luminesce in CH2Cl2 solution at room temperature, but they do emit light when present in poly(methyl methacrylate) films. Interestingly, DPM‐An and DPD‐An in the film forms display nearly identical emission (EM) spectra with respective maxima at 592 and 594 nm. In contrast, DPD‐An has a longer EM lifetime than does DPM‐An. Therefore, the dihydropentalene derivatives, exemplified by DPM‐An and DPD‐An, may be a family of substances in which excited state decay rate can be varied without changing EM wavelengths. [ABSTRACT FROM AUTHOR]

The article presents the results of a study of the temperature dependence of the dielectric constant ε' and the dielectric loss index ε" of the chlorobenzene-iodobenzene system at wavelengths λ = 6.32; 4.01; 3.21; 2.14; 1.18 and 0.75 V temperature range -40°++30°. The static dielectric constant was determined at a frequency of 7 MHz. The temperature dependence of the time of dielectric relaxation of molecules in the liquid state was determined. It was established that in the specified temperature-frequency range the dispersion region consists of two parts. Analysis of the temperature dependence of dielectric polarization relaxation in the system chlorobenzene-iodobenzene shows that the relaxation times of the components do not depend on their short-range order. It was also discovered that the rate graph showing the dependence of the logarithm of the relaxation time on the reciprocal of the temperature logt -1/T, consists of two parts and the value of the static dielectric permeability ε∞ is non-additive. To explain these results, it is assumed that clusters are formed in this system, the same as in the pure components. [ABSTRACT FROM AUTHOR]

As optical properties, the ultraviolet–visible (UV–Vis) absorption spectra of capsanthin‐based red natural dye are a decisive parameter for their usage in various applications. Thus, accurately predicting the maximum UV–Vis wavelength (λmax) values is critical in designing dye‐conjugated material. Extensive metadynamics simulations were carried out to generate capsanthin conformers at various levels of the extended tight‐binding method. Benchmarking the time‐dependent density‐functional theory (TD‐DFT) methods help understand the results of a particular functional and allows a comparison between results obtained with different functional. The long‐range correction (LC) scheme in LC‐TD‐DFT‐D4/ωB97X/def2‐SVP has been found to reproduce the experimental λmax, and exhibited the effect of conformational changes to the calculated wavelengths. On the other hand, an inexpensive yet efficient LC‐TD‐DFTB method reproduced the experimental λmax insensitive to conformational changes. [ABSTRACT FROM AUTHOR]

Scientific evidence showing the harmful effects of ultraviolet radiation on different ocular tissues has led manufacturers to incorporate UV-blocking monomers into contact lenses. In this study, the spectral and optical properties of contact lenses were analyzed in the ultraviolet and visible light wavelength ranges using the JASCO V-730 UV/Vis spectrophotometer device. The results obtained showed that the light transmittance in the wavelength (550nm) range to which the human eye is most sensitive in the lens samples examined was over 70 % and that B contact lens had a maximum value of 72,98 %. The largest cutting-edge wavelength value was obtained in the A contact lens as 376 nm. At 550 nm, the absorption spectra were found to be below 0.12. In terms of visual quality, visible light transmittance is expected to be high and ultraviolet alight transmittance is expected to be minimal. The degree of damage caused by the amount of ultraviolet light absorption increases. Among the contact lenses with and without ultraviolet-protected monomers, lens A did not transmit the UV-B wavelength region, while lens B transmitted UV-A and UV-B wavelengths. This result showed that the protection of lens A was higher. It is seen that the UV transmittance taken with the phocometer is 45% UV in A lens and 91% UV in B lens. The results obtained by UV/Vis spectrophotometer and phocometer supported each other. The results will contribute to the literature by revealing the importance of UV-protected monomer-containing contact lenses in vision equipment, and by enabling the development and selection of full-protection contact lenses. [ABSTRACT FROM AUTHOR]

The Chinese carbon dioxide measurement satellite (TanSat) has collected a large number of measurements in the solar calibration mode. To improve the accuracy of XCO2 retrieval, the Instrument Line Shape (ILS, also known as the slit function) must be accurately determined. In this study, we characterized the on-orbit ILS of TanSat by fitting measured solar irradiance from 2017 to 2018 with a well-calibrated high-spectral-resolution solar reference spectrum. We used various advanced analytical functions and the stretch/sharpen of the tabulated preflight ILS to represent the ILS for each wavelength window, footprint, and band. Using super Gaussian+P7 and the stretch/sharpen functions substantially reduced the fitting residual in O 2 A-band and weak CO 2 band compared with using the preflight ILS. We found that the difference between the derived ILS width and on-ground preflight ILS was up to −3.5% in the weak CO 2 band, depending on footprint and wavelength. The large amplitude of the ILS wings, depending on the wavelength, footprint, and bands, indicated possible uncorrected stray light. Broadening ILS wings will cause additive offset (filling-in) on the deep absorption lines of the spectra, which we confirmed using offline bias correction of the solar-induced fluorescence retrieval. We estimated errors due to the imperfect ILS using simulated TanSat spectra. The results of the simulations showed that XCO2 retrieval is sensitive to errors in the ILS, and 4% uncertainty in the full width of half maximum (FWHM) or 20% uncertainty in the ILS wings can induce an error of up to 1 ppm in the XCO2 retrieval. [ABSTRACT FROM AUTHOR]

Line intensities for carbon dioxide are measured with a novel spectroscopic approach, assisted by an optical frequency comb synthesizer for frequency calibration purposes. The main feature of the spectrometer consists in the exploitation of optical feedback from a V-shaped high-finesse optical resonator to effectively narrow a distributed feedback diode laser at the wavelength of 2 μm. Lasergas interaction takes place inside an isothermal cell, which is placed on the transmission from the cavity. High quality, self-calibrated, absorption spectra are observed in pure CO2 samples at different gas pressures, in coincidence with three lines of the R-branch of the ν1 + 2ν2 + ν3 band. Line intensities are determined using a global fitting approach in which a manifold of spectra are simultaneously analyzed across the range of pressures between 5 and 100 Torr, sharing a restricted number of unknown parameters. Various sources of uncertainty have been identified and carefully quantified, thus leading to an overall uncertainty ranging between 0.17% and 0.23%. The measured values are in a very good agreement with recent ab initio predictions. [ABSTRACT FROM AUTHOR]

We report on the Sm3+ and Sm3+:Yb3+-doped barium fluorotellurite glasses prepared using the conventional melting and quenching method. The spectroscopic characterisations were investigated with Raman and FTIR to evaluate the glasses' structural and hydroxyl (-OH) content. The Raman analysis revealed a structural modification in the glass network upon adding and increasing the Yb3+ concentration from a TeO3 trigonal pyramid to a TeO4 trigonal bi-pyramid polyhedral. At the same time, the FTIR measurements showed the existence of -OH groups in the glass. Thus, under the current experimental conditions and nominal composition, the -OH group contents are too large to enable an effective removal. The near-infrared region of the absorption spectra is employed to determine the nephelauxetic ratio and bonding parameters. The average nephelauxetic ratio decreases, and the bonding parameter increases with the increasing Yb3+ content in the glasses. A room temperature visible and near-infrared photoluminescence ranging from 500 to 1500 nm in wavelength and decay properties were investigated for glasses doped with Sm3+ and Sm3+-Yb3+ by exciting them with 450 and 980 nm laser sources. Exciting the Sm3+- and Sm3+-Yb3+-doped glasses by 450 nm excitation reveals a new series of photoluminescence emissions at 1200, 1293, and 1418 nm, corresponding to the 6F11/2 state to the 6HJ (J = 7/2, 9/2, 11/2) transitions. Under the 976 nm laser excitation, a broad photoluminescence emission from 980 to 1200 nm was detected. A decay lifetime decreased from ~244 to ~43 μs by increasing the Yb3+ content, ascribing to concentration quenching and the OH content. [ABSTRACT FROM AUTHOR]

The computational results of the features observed in the room-temperature Q-band absorption spectrum of free-base chlorin (H2Ch) are presented. The vibrational structures of the first and second excited singlet states were calculated based on a harmonic approximation using density functional theory and its time dependent extension within the Franck-Condon and Herzberg-Teller approaches. The outcome allowed to identify the experimental bands and to assign them to the specific vibrational transitions. A very good agreement between the simulated and measured wavelengths and their relative intensities provided the opportunity to predict the origin of the S0 → S2 transition which could not be determined experimentally. [ABSTRACT FROM AUTHOR]

Mechanochromic polymers are intriguing materials that allow to sense force of specimens under load. Most mechanochromic systems rely on covalent bond scission and hence are two-state systems with optically distinct "on" and "off" states where correlating force with wavelength is usually not possible. Translating force of different magnitude with gradually different wavelength of absorption or emission would open up new possibilities to map and understand force distributions in polymeric materials. Here, we present a mechanochromic donor-acceptor (DA) torsional spring that undergoes force-induced planarization during uniaxial elongation leading to red-shifted absorption and emission spectra. The DA spring is based on ortho-substituted diketopyrrolopyrrole (o-DPP). Covalent incorporation of o-DPP into a rigid yet ductile polyphenylene matrix allows to transduce sufficiently large stress to the DA spring. The mechanically induced deflection from equilibrium geometry of the DA spring is theoretically predicted, in agreement with experiments, and is fully reversible upon stress release. Force sensing using mechanochromic polymers is currently limited to two state systems and does not allow directly correlating the force with the absorption or emission wavelength. Here, the authors present a mechanochromic donor-acceptor torsional spring that undergoes force-induced planarization during uniaxial elongation leading to force dependent red-shifted absorption and emission spectra. [ABSTRACT FROM AUTHOR]

There is a large economic interest to characterize heads, hearts and tails fractions during fruit spirit distillation by simple, fast, low-volume and low-cost analytical methods. This study evaluated the potential of ultraviolet (UV)-visible-infrared spectroscopy (230-1000 nm) to characterize and differentiate these distillate fractions. Heads, hearts and tails fractions of 10 different fruit spirits were separated by sensory evaluation and investigated by absorbance spectroscopy. Principal component analysis indicated that UV spectroscopy at a wavelength range from 230 to 310 nm had the highest potential to differentiate all three distillate fractions. While all tails fractions showed significantly different UV spectra, a clear differentiation between heads and hearts fractions was limited. However, an additional UV spectroscopy of 100 mL subfractions sampled during the shift from heads to hearts in three additional distillations did reveal significant differences. The calculated integrals of the according best-fit trendline functions of the spectra indicated a trend towards reduced area-under-the-curve and zero-point values during the shift. This could be a new lead to implement an analytical method for in-line process control during fruit spirit production. [ABSTRACT FROM AUTHOR]

Reversible photoacids have been widely used in different areas for control of proton‐driven processes with light. Previously reported reversible photoacids rely on thermal relaxation to return to the low‐acidity ground state. Herein we report a photoacid that can be switched between low‐acidity and high‐acidity states by different wavelengths of light. The photoacid can be converted into a high‐acidity metastable state by 470 nm irradiation. The thermal relaxation of the metastable state is very slow and its half‐life in DMSO is 55 h. Irradiation with 365 nm light quickly induced the reverse reaction and reached a photostationary state. UV/Vis absorption spectra of the forward and reverse processes induced by 470 nm and 365 nm irradiation, respectively, have well‐matched isosbestic points. No decomposition was observed after the photoacid was switched by the two wavelengths of light for many cycles. Reversible patterning with both writing and erasing steps performed with light was demonstrated using a polymer thin film containing the photoacid and chlorophenol red as the proton acceptor. [ABSTRACT FROM AUTHOR]

Equation of motion coupled cluster calculations were performed on various structures of OH in clusters with one, two, three, and four water molecules to determine the energies of valence and charge transfer states. Motivation for these calculations is to understand the absorption spectrum of OH in water. Previous calculations on these species have confirmed that the longer wavelength transition observed is due to the A(²Σ) X(²Π) valence transition, while the shorter wavelength transition is due to a charge-transfer from H2O to OH. While these previous calculations identified the lowest energy charge-transfer state, our calculations have included sufficient states to identify additional solvent-to-solute charge transfer states. The minimum energy structures of the clusters were determined by application of the Monte Carlo technique to identify candidate cluster structures, followed by optimization at the level of second-order M0ller-Plesset perturbation theory. Calculations were performed on two structures of OH-H2O, three structures of OH-(H2O)2, four structures of OH-(H2O)3, and seven structures of OH-(H2O)4. Confirming previous calculations, as the number of water molecules increases, the energies of the excited valence and charge-transfer states decrease; however, the total number of charge-transfer states increases with the number of water molecules, suggesting that in the limit of OH in liquid water, the charge-transfer states form a band. [ABSTRACT FROM AUTHOR]

Photomediated-reversible-deactivation radical polymerisation (photo-RDRP) has a limited scope of available photocatalysts (PCs) due to multiple stringent requirements for PC properties, limiting options for performing efficient polymerisations under long wavelengths. Here we report an oxygen-mediated reductive quenching pathway (O-RQP) for photoinduced electron transfer reversible addition-fragmentation chain transfer (PET-RAFT) polymerisation. The highly efficient polymerisations that are performed in the presence of ambient air enable an expanded scope of available PCs covering a much-broadened absorption spectrum, where the oxygen tolerance of PET-RAFT allows high-quality polymerisation by preventing the existence of O2 in large amounts and efficient O-RQP is permitted due to its requirement for only catalytic amounts of O2. Initially, four different porphyrin dyes are investigated for their ability to catalyse PET-RAFT polymerisation via an oxidative quenching pathway (OQP), reductive quenching pathway (RQP) and O-RQP. Thermodynamic studies with the aid of (time-dependent) density functional theory calculations in combination with experimental studies, enable the identification of the thermodynamic constraints within the OQP, RQP and O-RQP frameworks. This knowledge enables the identification of four phthalocyanine photocatalysts, that were previously thought to be inert for PET-RAFT, to be successfully used for photopolymerisations via O-RQP. Well-controlled polymerisations displaying excellent livingness are performed at wavelengths in the red to near-infrared regions. The existence of this third pathway O-RQP provides an attractive pathway to further expand the scope of photocatalysts compatible with the PET-RAFT process and facile access to photopolymerisations under long wavelengths. Photomediated-reversible-deactivation radical polymerisation has a limited scope of available photocatalysts due to multiple stringent requirements of properties. Here the authors show, an oxygen-mediated reductive quenching pathway for photoinduced electron transfer reversible addition-fragmentation chain transfer polymerisation. [ABSTRACT FROM AUTHOR]

The absorption spectrum of CO2 in the wavelength range 120-160 nm is analyzed by means of quantum mechanical calculations performed using vibronically coupled potential energy surfaces of five singlet valence electronic states and the coordinate dependent transition dipole moment vectors. The thermally averaged spectrum, calculated for T = 190 K via Boltzmann averaging of optical transitions from many initial rotational states, accurately reproduces the experimental spectral envelope, consisting of a low and a high energy band, the positions of the absorption maxima, their FWHMs, peak intensities, and frequencies of diffuse structures in each band. Contributions of the vibronic interactions due to Renner-Teller coupling, conical intersections, and the Herzberg-Teller effect are isolated and the calculated bands are assigned in terms of adiabatic electronic states. Finally, diffuse structures in the calculated bands are vibronically assigned using wave functions of the underlying resonance states. It is demonstrated that the main progressions in the high energy band correspond to consecutive excitations of the pseudorotational motion along the closed loop of the CI seam, and progressions differ in the number of nodes along the radial mode perpendicular to the closed seam. Irregularity of the diffuse peaks in the low energy band is interpreted as a manifestation of the carbene-type 'cyclic' OCO minimum. [ABSTRACT FROM AUTHOR]

A distributed feedback laser with a wavelength of 2.8 µm was used to measure the species produced by water vapor glow discharge. Only the absorption spectra of OH radicals and transient H2O molecules were observed using concentration modulation (CM) spectroscopy. The intensities and orientations of the absorption peaks change with the demodulation phase, but the direction of one absorption peak of H2O is always opposite to the other peaks. The different spectral orientations of OH and H2O reflect the increase or the decrease of the number of particles in the energy levels. If more transient species can be detected in the discharge process, the dynamics of excitation, ionization, and decomposition of H2O can be better studied. This study shows that the demodulation phase relationship of CM spectrum can be used to study the population change of molecular energy levels. [ABSTRACT FROM AUTHOR]

Changes in the absorption spectra of aqueous solutions of modern chlorinated photosensitizing drugs for photodynamic therapy "Revixan" (Areal, Russia) and "Chloderm" (Chloderm, Russia) in the range of 600–700 nm depending on the intensity and time of exposure to LED emission with a wavelength of 656 ± 10 nm have been studied. The parameters of the CIE Lab color model of the "Revixan" water solution image before and after LED exposure have been studied. In the range of 400–900 nm, the changes in the absorption spectra of an aqueous solution of methylene blue with different initial concentrations after exposure to LED emission with a wavelength of 656 ± 10 nm and an intensity of 180 ± 20 mW/cm2 have been studied. It has been shown that the effect of LED emission changes the absorption spectra of the studied substances and increases the parameter L (brightness) of the CIE Lab color model for "Revixan". An increase in the intensity of the LED emission and exposure time causes a decrease in the absorption for "Revixan" and "Chloderm" in the range of 600–700 nm and a shift of the peak of the absorption band lying in this range to the infrared region. The effect of the LED emission on an methylene blue aqueous solution causes a decrease in its absorption in the range of 400–900 nm. [ABSTRACT FROM AUTHOR]

A series of Sc:Yb:Tm:LiNbO3 crystals with variable Sc3+ (0, 1, 2, and 3 mol%) concentration are grown by the Czochralski method. The effective distribution coefficients of Sc3+, Yb3+, and Tm3+ ions in the Sc:Yb:Tm:LiNbO3 crystals are determined by inductively coupled plasma atomic emission spectrometer. Sc3+ ions distribute uniformly in crystals when Sc3+ concentration reaches up to 3 mol%. The influence of Sc3+ concentration on the dopant occupancy and defect structure of Sc:Yb:Tm:LiNbO3 crystals is investigated by IR transmission spectra. Threshold concentration of Sc3+ ions in Sc:Yb:Tm:LiNbO3 crystals is nearly 3 mol%. By analyzing UV–vis–NIR absorption spectra, absorption property of Sc:Yb:Tm:LiNbO3 crystals is improved by doping Sc3+ ions. Additionally, the Sc:Yb:Tm:LiNbO3 crystals can be pumped by commercially available high power AlGaAs LDs. [ABSTRACT FROM AUTHOR]

The stable polyene cation‐radical containing the 7,8‐dihydrobenzo[cd]furo[2,3–f]indol terminal groups was synthesized and the features of its lowest electron transitions were studied, in detail. The electronic structure and absorption spectra of the polyene cation‐radical obtained, was compared with the electronic and spectral properties of the corresponding neutral poleynes, dications and related polymethine dye having the same terminal groups. While polyene and its dication absorb in the relative short wavelength spectral region, the polymethine‐cation absorbs in the long wavelength region; it is shown that two splitting bands appear in the spectra of the polyenic cation‐radical: the low‐ intensive long wavelength band (≈ 1200 nm) and of the high‐ intensive short wavelength band (≈800 nm); they take correctly into consideration splitting of excited states, generated by α‐ and β‐electrons. [ABSTRACT FROM AUTHOR]

Inactivation properties of visible light are of increasing interest due to multiple possible fields of application concerning antibacterial treatment. For violet wavelengths, the generation of reactive oxygen species by porphyrins is accepted as underlying mechanism. However, there is still little knowledge about photosensitizers at blue wavelengths. While flavins were named as possible candidates, there is still no experimental evidence. This study investigates the photoinactivation sensitivity of Staphylococcus carnosus to selected wavelengths between 390 and 500 nm in 10‐ to 25‐nm intervals. Absorption and fluorescence measurements in bacterial lysates confirmed inactivation findings. By means of a mathematical calculation in MATLAB®, a fit of different photosensitizer absorption spectra to the measured action spectrum was determined to gain knowledge about the extent to which specific photosensitizers are involved. The most effective wavelength for S. carnosus at 415 nm could be explained by the involvement of zinc protoporphyrin IX. Between 450 and 470 nm, inactivation results indicated a broad plateau, statistically distinguishable from 440 and 480 nm. This observation points to flavins as responsible photosensitizers, which furthermore seem to be involved at violet wavelengths. A spectral scan of sensitivities might generally be an advantageous approach for examining irradiation impact. [ABSTRACT FROM AUTHOR]

The center line slope (CLS) method is often used to extract the frequency-frequency correlation function (FFCF) from 2D IR spectra to delineate dynamics and to identify homogeneous and inhomogeneous contributions to the absorption line shape of a system. While the CLS method is extremely efficient, quite accurate, and immune to many experimental artifacts, it has only been developed and properly applied to systems that have a single vibrational band, or to systems of two species that have spectrally resolved absorption bands. In many cases, the constituent spectra of multiple component systems overlap and cannot be distinguished from each other. This situation creates ambiguity when analyzing 2D IR spectra because dynamics for different species cannot be separated. Here a mathematical formulation is presented that extends the CLS method for a system consisting of two components (chemically distinct uncoupled oscillators). In a single component system, the CLS corresponds to the time-dependent portion of the normalized FFCF. This is not the case for a two component system, as a much more complicated expression arises. The CLS method yields a series of peak locations originating from slices taken through the 2D spectra. The slope through these peak locations yields the CLS value for the 2D spectra at a given Tw. We derive analytically that for two component systems, the peak location of the system can be decomposed into a weighted combination of the peak locations of the constituent spectra. The weighting depends upon the fractional contribution of each species at each wavelength and also on the vibrational lifetimes of both components. It is found that an unknown FFCF for one species can be determined as long as the peak locations (referred to as center line data) of one of the components are known, as well as the vibrational lifetimes, absorption spectra, and other spectral information for both components. This situation can arise when a second species is introduced into a well characterized single species system. An example is a system in which water exists in bulk form and also as water interacting with an interface. An algorithm is presented for back-calculating the unknown FFCF of the second component. The accuracy of the algorithm is tested with a variety of model cases in which all components are initially known. The algorithm successfully reproduces the FFCF for the second component within a reasonable degree of error. [ABSTRACT FROM AUTHOR]

Electronic absorption spectra of linear HC2n+1H+ (n=2–7) were recorded in 6 K neon matrices following their mass-selective deposition. Four new electronic band systems are identified; the strongest E 2Πg/u←X 2Πu/g lies in the UV and the second most intense C 2Πg/u←X 2Πu/g is located in the visible range. The known A 2Πg/u←X 2Πu/g absorption is an order of magnitude weaker than C 2Πg/u←X 2Πu/g. Transitions to the B and D states are also discussed. The wavelengths of the HC2n+1H+ (n=2–7) electronic systems obey a linear relation as a function of the size of the cations, similar to other carbon chains. The B 3Σu-←X 3Σg- transition in the UV of neutral HC2n+1H (n=4–7) has also been identified upon photobleaching of the cations trapped in the matrices. [ABSTRACT FROM AUTHOR]

The absorption spectrum of the H2 molecule was studied at high resolution in the 81–72 nm spectral range. A detailed analysis of the D′ 1Πu→X 1Σg+ electronic band system is reported. In the spectrum, more than 70 new lines were assigned. For wavelengths longer than 75 nm, the D′ 1Πu+ and 1Πu- components show a clearly different behavior: Τhe 1Πu+ one dissociates into H(1s)+H(n=2) whereas the 1Πu- one leads to molecular fluorescence. For shorter wavelengths, both components are predissociated into H(1s)+H(n=3). The predissociation yields, the dissociation widths, and the absolute values of the transition probabilities were measured over the vibrational progression from v′=3 to 17, i.e., up to the dissociation limit. The comparison between these absolute transition probabilities and the values calculated in the adiabatic and nonadiabatic approximations demonstrates clearly the importance of nonadiabatic couplings. [ABSTRACT FROM AUTHOR]

Wavelength dependence of saturable absorption (SA) and reverse saturable absorption (RSA) of zinc phthalocyanine was studied using 10 Hz, 8 ns pulses from a tunable laser, in the wavelength range of 520–686 nm, which includes the rising edge of the Q band in the electronic absorption spectrum. The nonlinear response is wavelength dependent and switching from RSA to SA has been observed as the excitation wavelength changes from the low absorption window region to higher absorption regime near the Q band. The SA again changes back to RSA when we further move over to the infrared region. Values of the imaginary part of third order susceptibility are calculated for various wavelengths in this range. This study is important in identifying the spectral range over which the nonlinear material acts as RSA based optical limiter. [ABSTRACT FROM AUTHOR]

The CdS and CdS-Ag core-shell quantum dots (QDs) have been prepared. The nanostructures of the QDs were revealed by transmisson electron microscopy and absorption spectra, respectively. The third-order nonlinear optical properties of the core-shell QDs have been studied by using Z-scan technique with femtosecond pulses at the wavelength of 790 nm. The value of the effective nonlinear absorption coefficient βeff of CdS-Ag QDs is measured to be about 16.8 cm/GW, which is about 400 times larger than that of bare CdS QDs of 3.9×10-2 cm/GW. The nonlinear refraction index γ of CdS-Ag QDs is about -2.3×10-4 cm2/GW, which is about 200 times larger than that of bare CdS QDs of 1.0×10-6 cm2/GW. [ABSTRACT FROM AUTHOR]

This work employs the Z-scan technique with 120 fs pulses to investigate the singlet excited state absorption spectra of tetrapyridyl and tetrasulfonatophenyl porphyrins. We have used a three-energy-level model to adjust Z-scan curves in order to obtain the singlet excited absorption cross section from 460 to 800 nm. Starting from these values, we determine the spectra of the ratio between excited and ground singlet state absorption cross sections, whose values are as good as the best found in the literature for reverse saturable absorbers. The results obtained point these porphyrins as good candidates for applications in optical limiting of ultrashort pulses. [ABSTRACT FROM AUTHOR]

The UV/visible spectra of a series of indigo derivatives have been evaluated by using ab initio methods. The combination of the Polarizable continuum model for estimating bulk solvent effects with the TD-B3LYP/6-311+G(2d,p)//B3LYP/6-311G(d,p) level of approximation, leads to an accurate description of the wavelength of maximum absorption of indigoïds compounds. Using this procedure, we have assessed the effects of both the surroundings (solvent and solid state) and the substitution pattern. For the latter, we obtained a mean absolute deviation of only 7 nm (0.02 eV) compared to experiment, for a set of 86 molecules/solvents. [ABSTRACT FROM AUTHOR]

Simulated absorption spectra of twelve donors based on D-π-D (a) and D-π-A-π-D (b) topologies with the Solar Flux for AM 1.5G. • A comparative analysis of different shapes (star, π, H and X) and different topologies (D-π-D and D-π-A-πD) molecules is done. • DFT and TD-DFT calculations has been carried out to know their optical and charge transfer properties. • On the basis of results, we suggest best performing donor materials for organic solar cells. As substantial building units, different shapes and topologies enhance optical and electronic properties. Hence, in this paper, twelve anisotropic molecules of different shapes (star or S, π and H) based on D-π-D and D-π-A-π-D topologies have been designed and investigated theoretically applying a double overlapping wave band strategy for organic photovoltaic applications. This analysis indicates that stronger electron withdrawing A1 fragment, D-π-A-π-D topology, star and π shaped molecules impart toward lower LUMO and smaller Eg values than those of D-π-D type and X or H- shaped molecules. According to TD-DFT calculations, start-shaped molecules show broader spectra with intense peaks in both topologies covering not only visible region but also IR region of spectrum. Furthermore, the optical analysis also demonstrates that π-π* absorptions in short and middle wavelength region are because of central anisotropic multibranched donor (Bi)n-2DF-(Bi)n moiety, where A components exhibit absorptions in the ML wavelength region of spectrum. In General, smaller λ e and λ h values are exhibited for star and π-shaped molecules because of better dimensionality, whereas H and X-shaped (D1b) display more or less similar values. The predicted electron and hole mobility values for DAD1-S are as; µ e = 2.46 (cm2/Vs) and µ h = 0.0540 (cm2/Vs), respectively. Thus, results of these calculation prove that our theoretical studies provide a deep insights to confirm that investigated donor compounds would be appropriate vs PDIs acceptors for OSCs. [ABSTRACT FROM AUTHOR]

Highlights • Sensitive ultraviolet absorption based spectroscopy measurements of oxygen was reported. • An invariable absorption line shape based pressure measurement approach was designed. • A simplified, portable, and highly sensitive dual sensing system for oxygen and pressure was built. • Oxygen concentration detection limit of 150 ppm and pressure detection limit of 180 Pa were achieved. Abstract In this study, a highly sensitive monitoring system for dual sensing of oxygen and pressure has been developed. The absorption of oxygen in the wavelength range of 186–196 nm was observed and the corresponding absorption cross-section of oxygen in this band was achieved. An approach based on differential optical absorption spectroscopy was used to describe the concentration of oxygen. The detection limit of oxygen was determined to be 150 ppm per meter. No relation between pressure and oxygen absorption line shape in the related wavelength band was confirmed. Based on the absorption of oxygen, pressure detection was realized and a detection limit of 180 Pa was obtained. A dual sensing system for oxygen and pressure was constructed. [ABSTRACT FROM AUTHOR]

Biases in absorption coefficients measured using a filter-based absorption photometer (Tricolor Absorption Photometer, or TAP) at wavelengths of 467, 528 and 652 nm are evaluated by comparing to measurements made using photoacoustic spectroscopy (PAS). We report comparisons for ambient sampling covering a range of aerosol types including urban, fresh biomass burning and aged biomass burning. Data are also used to evaluate the performance of three different TAP correction schemes. We found that photoacoustic and filter-based measurements were well correlated, but filter-based measurements generally overestimated absorption by up to 45%. Biases varied with wavelength and depended on the correction scheme applied. Optimal agreement to PAS data was achieved by processing the filter-based measurements using the recently developed correction scheme of Müller et al. (2014), which consistently reduced biases to 0-17% at all wavelengths. The biases were found to be a function of the ratio of organic aerosol mass to light-absorbing carbon mass although applying the Müller et al. (2014) correction scheme to filter-based absorption measurements reduced the biases and the strength of this correlation significantly. Filter-based absorption measurement biases led to aerosol single-scattering albedos that were biased low by up to 0.07 and absorption Ångström exponents (AAE) that were in error by ±0.54. The discrepancy between the filter-based and PAS absorption measurements is lower than reported in some earlier studies, and points to a strong dependence of filter-based measurement accuracy on aerosol source type. [ABSTRACT FROM AUTHOR]

We calculated the changes of refractive index and absorption coefficient in Ge induced by the Franz-Keldysh (FK) effect and free carrier dispersion (FCD) effect, taking advantage of reported absorption spectra.The FK effect is weak near the indirect absorption edge of Ge. FCD effect can induce a much larger change of refractive index. In the wavelength range of 2–10 μm, theoretical formulas about dependences of the changes of absorption coefficient and refractive index on the change of carrier concentrations are presented. In addition, FCD effects in N-type and P-type Ge are compared. [ABSTRACT FROM AUTHOR]

This article reports on laser absorption spectroscopy of iodine gas between 915 nm and 985 nm. This wavelength range is scanned utilizing a narrow linewidth and mode-hop-free tunable diode-laser whose frequency is actively controlled using a calibrated wavelength meter. This allows us to provide an iodine atlas that contains almost 10,000 experimentally observed reference lines with an uncertainty of 50 MHz. For common lines, good agreement is found with a publication by Gerstenkorn and Luc (1978). The new rich dataset allows existing models of the iodine molecule to be refined and can serve as a reference for laser frequency calibration and stabilization. [ABSTRACT FROM AUTHOR]

We present the results of ground based observations and model analysis of transits of exoplanets WASP-33b, WASP-43b, WASP-104b, and HD 219134b. Broadband transmission spectra (dependence of the observed radii on wavelength) have been plotted for all exoplanets, ranging from the near-UV to the IR region. We show that the transmission spectrum of WASP-33b is, within errors, flat in the range of 3800 Å to 12 000 Å. The derived broadband spectrum of WASP-43b is also flat in the first approximation, although other authors have reported the presence of absorption lines of various chemical elements in the narrow bands. Model spectra of WASP-43b taken from the literature and based on IR data allowed us to obtain a direct estimate of its nighttime temperature. We present and analyze the results of ground based observations which confirm the discovery of a transiting super-Earth in the HD 219134 star system. Signs of this planet’s existence were discovered earlier during the radial velocity analysis of the star, as well as transit observations with the Spitzer space telescope in the IR.At the estimated time, we registered a transit in the near-UV range several times. The transit depth measured in the U-band of the Johnson photometric system amounts to 0.13% ± 0.027%, which is deeper than the one based on Spitzer measurements. We discuss the possible causes of this difference. [ABSTRACT FROM AUTHOR]

Stable-isotopically-labeled internal standards are commonly incorporated in methods for trace analysis that utilize mass spectrometric detection. They closely mimic the physicochemical properties of the analyte, but their signal is easily differentiable based on a change in molecular mass. To investigate the potential to transfer methods incorporating such internal standards for analysis by vacuum ultraviolet detection, a study was conducted to compare the spectral shape (from 125 to 240 nm) of stable-isotopically-labeled compounds with their non-labeled counterparts. Gas chromatography – vacuum ultraviolet spectroscopic analysis was performed for a series of benzene isotopologues, as well as for clinically- and environmentally-relevant standard compounds and their deuterated counterparts. The absorption characteristics of the benzene isotopologues were evaluated based on similarity (normalized spectra), as well as on their magnitude of absorption. In general, very minor differences in absorption spectra were observed; however, increasing degree of deuteration did generally increase the spectral difference between labeled and non-labeled analytes. Sum of squared residuals were used as quantitative measures to assess spectral similarity (and dissimilarity). Theoretical computation of absorption spectra for benzene using time-dependent density functional theory was also examined; though, further work is needed in this area to extend the analysis to isotopologue analysis. [ABSTRACT FROM AUTHOR]

The frequency of the quarter wavelength resonance in the sound absorption spectra due to a thin hard-backed rigid-porous layer can be influenced by the design of its microstructure as well as its thickness. Microstructures considered include parallel arrays of identical cylindrical, slit-like or rectangular pores with deep sub-wavelength cross sections inclined to the surface normal, cylindrical annular pores, slits with log-normal width distributions, slits with cross sections that vary in a sinusoidal manner and slits with two distinct widths (dual porosity). Formulae that predict the bulk acoustical properties due to these microstructures are presented and used to explore the extent to which specific microstructures could be used separately or in combination to improve low-frequency absorption. Predicted normal incidence absorption coefficient spectra are compared using microstructural dimensions that would be feasible for 3D printing. The most effective microstructures are predicted to be slits with sinusoidally-varying widths, or with two distinct widths, inclined to the surface normal at 70°. The quarter wavelength layer resonances predicted in absorption coefficient spectra using these microstructures are comparable with those predicted for layers of the same thickness and bulk porosity having cylindrical pores with dead-end branches. [ABSTRACT FROM AUTHOR]

The reddish orange phosphor with nanostructure is proposed to improve the efficiency of solar cells in this research. According to the absorption spectrum of c-Si solar cell, only the light with wavelength less than 1000 nm can be absorbed, and the strongest absorption band locates during wavelengths 500 to 900 nm. Ultraviolet (UV) light with high energy photons can be absorbed by solar cells as well, but the most energy is converted into heat and this phenomenon results in the lower efficiency. The YBO:Sm nano-phosphor with emission bands locating at 570, 610 and 655 nm is proposed to convert UV light into reddish orange light absorbed by solar cells. By means of this scheme, the converting efficiency of solar cells can be improved. The nano-scaled YBO:Sm phosphor was obtained by the chemical co-precipitation method and thermal treatments. The average diameter of particles is about 60 nm. From the PLE spectrum, this phosphor can be stimulated strongly by light with wavelength locating at 405 nm and emit the light bands locating at 570, 610 and 655 nm. This three emission bands originate from the following electron transitions G → H, G → H, and G → H, respectively. In our experiments, the YBO phosphor with 1% dopant Sm possesses the optimal emission efficiency and can be applied to improve the converting efficiency of solar cells. [ABSTRACT FROM AUTHOR]

Conventional absorption spectroscopy (CAS) with a blank reference has only a slight capacity to detect high concentrations at characteristic wavelengths owing to the corresponding large molar absorption coefficient (ε) on the scale of 103 or 104 cm-1 M-1. To monitor concentrated analytes as high as the molar range in a plating bath and on a chemical production line, we propose a new approach using sideband differential absorption spectroscopy (SDAS). SDAS is obtained by subtracting the absorption spectra of the samples, A(λ,Cx), from that of a reference containing a concentrated standard analyte, A(λ,Cref>Cx), resulting in concave spectra with peaks at the sideband of conventional spectra with generally low ε values on the scale of 100 cm-1 M-1 or less. The negative absorbance changes linearly with the sample concentration at a certain peak wavelength, obeying Lambert-Beer's law. In this work, SDAS was obtained and verified using inorganic and organic substances, such as chromate potassium, rhodamine B, and paracetamol. [ABSTRACT FROM AUTHOR]

We study the plasmon resonances, which occur in the two-dimensional problem of diffraction of a plane wave on a glass cylinder encased in a silver layer, under the assumption that the media interface boundaries are confocal ellipses. Numerical methods are used to calculate the spectra of scattering and absorption in the optical wavelength range. The obtained analytical expressions allow determining the resonance parameters of the structure within the quasistatic approximation. [ABSTRACT FROM AUTHOR]

• High efficiency high brightness cw cryogenic Nd:YAP laser is reported. • Multi-wavelength laser operation at 1064, 1072 and 1079 nm is analyzed. • The brightness is about 130 MW/cm2·sr at the maximum output power at 180 K. A high efficiency high brightness continuous wave (cw) cryogenic a-cut Nd:YAlO 3 (Nd:YAP) laser is demonstrated with dual wavelengths at 1072 and 1079 nm. By exploring the temperature dependence of the fluorescence and the absorption spectra from the a-cut Nd:YAP crystal, the feasibility of multi-wavelength laser operation is analyzed. At an optimal temperature of ∼180 K, a maximum output power for dual-wavelength operation is reached 2.1 W at an incident pump power of 4.6 W, corresponding to a slope efficiency up to 50 %. The average beam quality factor is measured to be 1.17, indicating a brightness of ∼130 MW/cm2·sr. These results present, to the best of authors knowledge, the highest brightness and slop efficiency for any multi-wavelength Nd:YAP laser. Such brightness multi-wavelength laser source with high beam quality has important applications in scientific research, laser radar and astronomy domains, especially in obtaining terahertz (THz) sources. [ABSTRACT FROM AUTHOR]

The absorption characteristics of three types of trace gases (sulfur dioxide, nitrogen dioxide and nitric oxide) were simulated through line-by-line integral algorithm utilizing the HITRAN2012 database. The effect of temperature, pressure, and other interfering gases were analyzed in the mid-infrared band (2–5 μm) and suitable sets of wavelengths were proposed for the mid-infrared differential absorption lidar (MI-DIAL). The absorption spectrum of one typical trace gas was measured and it was found to be reasonably consistent with that of the simulated one. The lidar system simulated results showed that the selected sets of wavelength can be used in MI-DIAL to detect the polluted gases. [ABSTRACT FROM AUTHOR]

Two sets of bis-aryl Schiff bases that contain 4(or 4′)-OH and 2(or 2′)-OH were synthesized. The first set consists of 4-HOArCH=NArY and XArCH=NArOH-4′, and the second set consists of 2-HOArCH=NArY and XArCH=NArOH-2′. Their ultraviolet absorption spectra were measured and investigated. A very interesting phenomenon was observed by analyzing their wave number νmax (cm−1) of longest wavelength maximum λmax (nm) of ultraviolet. Compared with the change regularity of the νmax of XArCH=NArY (where the X and Y excluded OH), the 4′-position hydroxyl (4′-OH) and 2′-position hydroxyl (2′-OH) have abnormal performance. The details are the following: the 4′-OH contributes an additional red shift to the νmax of XArCH=NArOH-4′ (λmax increase), whereas the 2′-OH contributes an additional blue shift to the νmax of XArCH=NArOH-2′ (λmax decrease). In addition, there are ortho steric effects of all 2-OH and 2′-OH on the νmax for 2-HOArCH=NArY and XArCH=NArOH-2′, and the ortho steric effect contributes a red shift to their νmax. These experimental facts can provide an important theoretical reference for us using aryl Schiff base compounds as optical materials and performing the molecular design. [ABSTRACT FROM AUTHOR]