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Comparison of total ozone column (TOC) measurements from ground-based Dobson and Brewer spectrophotometers and from various satellite instruments generally reveals seasonally varying differences of a few percent. A large part of these differences has been attributed to the operationally used Bass & Paur ozone cross-sections and the lack of accounting for varying stratospheric temperatures in the standard total ozone retrieval for Dobson. This paper demonstrates how the use of new ozone absorption cross sections from the University of Bremen (Weber et al., 2016), as recommended by the committee on Absorption Cross-Sections of Ozone, the application of appropriate slit functions, especially for the Dobson instrument (Bernhard et al. 2005), and the use of climatological values for the effective ozone layer temperature (Teff), e.g. from TEMIS, essentially eliminate these seasonally varying differences between Dobson and Brewer total ozone data. Applying this approach to the existing global network of Dobson spectrometers will reduce the uncertainty of their total ozone data, from previously 3 to 4% to better than 2.0% at most locations. [ABSTRACT FROM AUTHOR]

Upconverter/MoS2 heterostructure thin films fabricated by hydrothermal technique are confirmed by X‐ray diffraction and Raman studies. Field‐emission scanning electron microscopy (FESEM) and high‐resolution transmission electron microscopy (HRTEM) reveal the nanobelt structured MoS2 mingled with trapezoid structure fluoride upconverters and sphere‐shaped oxide upconverters. The films exhibit green (H11/22 to I15/24) and red (F9/24 to I15/24) emission. The influence of upconverters on the nonlinear absorption of MoS2 is exploited by Z‐scan technique using nanopulsed laser. Estimated ground‐state absorption cross section is higher than the excited‐state absorption cross section of the samples and it confirms the occurrence of saturable absorption. CeO2:Yb,Er@MoS2 exhibits stronger saturable absorption due to synergetic effects like higher linear absorption coefficient at 532 nm, stronger green emission, and reduced size. Results pave way for the design of optical switches, Q‐switches, and mode lockers using upconverter integrated MoS2 thin films. [ABSTRACT FROM AUTHOR]

A comparison between storm‐time TIMED/GUVI FUV spectra in thermospheric composition disturbed (O/N2 <∼140 km> depleted and NO <∼110 km> enhanced) and undisturbed regions reveals the following features: (1) A clear decrease in N2 LBHS (140–150 nm) band intensities compared to that between 150 and 160 nm; (2) A significant spectral decrease around O 164.1 nm; (3) Two enhanced peaks between 170 and 185 nm. The feature (2) is clearly due to atomic oxygen density decrease in the low thermosphere. The feature (3) is caused by storm‐time production and transport of nitric oxide. An AURIC simulation reproduced feature (1) confirming that storm‐time enhancement in O2 density (∼120–170 km) and the wavelength dependent O2 absorption cross section are the source of observed feature (1). On the other hand, the feature (1) was not observed in the regions without O/N2 depletion. This further supports that O2 density enhancement is responsible for feature (1). Plain Language Summary: Observations by a FUV spectrograph imager on NASA TIMED satellite revealed two interesting features in the storm‐time disturbed thermosphere: (1) a relative decrease in N2 LBH intensities at 140–150 nm versus 150–160 nm, (2) significant decrease in O 164.1 nm radiance and enhanced emission between 170 and 185 nm. The feature (2) is well known and due to O density depletion and production of nitric oxide. The feature is not well understood. A model simulation indicates the feature (1) is due to storm‐time O2 density increase and wavelength dependent O2 absorption cross section which peaked around 140 nm. This result indicates that FUV spectrograph imager is capable to detect storm‐time O2 density changes. Key Points: (1) FUV spectral difference between storm‐quiet time shows a relative decrease in N2 LBH intensities at 140–150 nm versus 150–160 nmThe FUV spectrograph difference between undisturbed regions did not show the above feature(3) Simulations confirm indicate that enhanced O2 density and absorption causes the observed FUV spectral differences [ABSTRACT FROM AUTHOR]

We report on photoluminescence emission in copper iodide bulk single crystals induced by two- and three-photon absorption around 1.525 eV. These non-linear optical processes are investigated utilizing density-dependent, steady-state, as well as time-resolved photoluminescence spectroscopy as a function of the excitation energy. Using an excitation energy that corresponds to half of the bandgap energy, the observed photoluminescence intensity dependence on the excitation power shows an almost parabolic behavior. By further reduction of the photon energy, a cubic contribution is observable, which increases with decreasing excitation energy. The experimentally observed behavior can be well described by taking into account two- and three-photon absorption. By a simultaneous analysis of the intensity behavior for all used excitation energies, we determined a ratio between the two- and three-photon absorption cross section on the order of σ 0 (3) / σ 0 (2) ≈ 10 − 28 cm 2 s. [ABSTRACT FROM AUTHOR]

From analytical approximations, for small scattering angles, we also know that the BH charge does not contribute to the dominant term of the differential SCS, in this regime (see, e.g., Refs. Concerning the absorption cross section (ACS), the authors of Ref. [[12]] obtained that the total ACS decreases as we consider higher BH charge values, and it oscillates around the corresponding geometric cross section, in agreement with some results presented in the literature. Absorption and scattering properties of matter fields in the background of black hole (BH) spacetimes have been investigated in several standard scenarios since the 1960s (see, e.g., Refs. On-axis scattering of scalar fields by charged rotating black holes. [Extracted from the article]

Two-photon absorption spectra and two-photon absorption cross sections of Cl-substituted diphenylacetylenes (ClDPAs) were investigated by optical-probing photoacoustic spectroscopy and quantum chemical calculations for the first time. The two-photon absorption spectra of ClDPAs exhibited intense two-photon absorption bands at around 480 nm, which are forbidden by one-photon absorption. The two-photon absorption cross sections σ(2) of o-, m-, and p-ClDPAs at 476 nm were determined to be 22 ± 1, 23 ± 1, and 38 ± 2 GM, respectively. Compared with diphenylacetylene (DPA) (27 GM at 472 nm), the σ(2) values of o- and m-ClDPAs were lower, while that of p-ClDPA was higher. Simulated two-photon absorption spectra using the TD-B3LYP/6-311+G(d,p) level of calculations within the Tamm-Dancoff approximation, based on the three-state model, well agreed with the experimental results. The difference in the σ(2) values of DPA and ClDPAs was responsible for those in the transition dipole moments between the intermediate and the final states. [ABSTRACT FROM AUTHOR]

Interest in Criegee intermediates (CIs), often termed carbonyl oxides, and their role in tropospheric chemistry has grown massively since the demonstration of laboratory‐based routes to their formation and characterization in the gas phase. This article reviews current knowledge regarding the electronic spectroscopy of atmospherically relevant CIs like CH2OO, CH3CHOO, (CH3)2COO and larger CIs like methyl vinyl ketone oxide and methacrolein oxide that are formed in the ozonolysis of isoprene, and of selected conjugated carbene‐derived CIs of interest in the synthetic chemistry community. Of the aforementioned atmospherically relevant CIs, all except CH2OO and (CH3)2COO exist in different conformers which, under tropospheric conditions, can display strikingly different thermal loss rates via unimolecular and bimolecular processes. Calculated photolysis rates based on their absorption properties suggest that solar photolysis will rarely be a significant contributor to the total loss rate for any CI under tropospheric conditions. Nonetheless, there is ever‐growing interest in the absorption cross sections and primary photochemistry of CIs following excitation to the strongly absorbing 1ππ* state, and how this varies with CI, with conformer and with excitation wavelength. The later part of this review surveys the photochemical data reported to date, including a range of studies that demonstrate prompt photo‐induced fission of the terminal O–O bond, and speculates about possible alternate decay processes that could occur following non‐adiabatic coupling to, and dissociation from, highly internally excited levels of the electronic ground state of a CI. [ABSTRACT FROM AUTHOR]

In this work, we investigate the scattering of massless plane scalar waves by the high dimensional non-commutative Schwarzschild–Tangherlini black hole. We use the partial wave approach to determine the scattering and absorption cross sections in the incident wavelength range. Our numerical results demonstrate that the bigger the non-commutative parameter, the smaller the maximum value of the related partial absorption cross section, however the tendency is slightly. We also discovered that when the non-commutative parameter is weak, the absorption cross section of the high dimensional black hole oscillates in the low frequency zone. The total absorption cross section oscillates around the geometrical optical limit in the high frequency range, and the scattering characteristics of black holes with various parameters are visibly different. The influence on the differential scattering cross section is particularly pronounced at large angles. [ABSTRACT FROM AUTHOR]

Observations of solar irradiance made from space since 2003 with 0.1 nm spectral resolution at wavelengths from 115 to 310 nm and 0.5 nm spectral resolution at wavelengths from 260 to 500 nm are used to construct a new model, NRLSSI2h, of solar irradiance variability with higher spectral resolution than the 1 nm NRLSSI2 model used to specify the NOAA Solar Irradiance Climate Data Record. The new model better resolves irradiance variability in specific emission and absorption features that are directly attributable to atoms and molecules in the Sun's atmosphere. Singularly prominent is spectral irradiance variability at 379–389 nm, dominated by the CN molecular band system; irradiance in this 10 nm band increased 0.078 W m−2 during solar cycle 23, contributing 4.6% of the 1.7 W m−2 concurrent total solar irradiance increase. Irradiance variability at wavelengths from 300 to 400 nm, a region dominated by multiple spectral features, is a factor of 2–5 smaller in the new model than estimated by semiempirical models that use radiative transfer codes to calculate the contrasts of faculae and sunspots, which alter the temperature‐dependent densities of these species relative to the surrounding continuum. Solar atmosphere temperature and composition profiles in radiative transfer models may therefore not be realistic or their atomic and molecular databases may be incomplete. Improved colocation of spectral features in solar irradiance and the absorption cross sections of molecular oxygen and ozone with the new model may allow higher fidelity calculations of energy deposition in Earth's atmosphere. Key Points: A new high‐resolution (0.1–0.5 nm) solar irradiance variability model, NRLSSI2h, captures larger UV spectral line variabilityAt 300–400 nm, where spectral features dominate, NRLSSI2h estimates 2–5 times less solar cycle variability than radiative transfer modelsAtmospheric absorption of solar radiation differs using NRLSSI2h relative to the 1 nm NRLSSI2 model (at 121.6 nm, 34% decrease at 88 km) [ABSTRACT FROM AUTHOR]

[Display omitted] • Double and triple functionalization of oxindole-based molecular motors is possible retaining the desirable qualities of these type of molecular machines. • Establishing a push–pull system in oxindole-based molecular motors shifts the absorption maximum further into the visible region and increases their two-photon absorption cross section. • First time demonstration of an oxindole based molecular motor operated with near infra-red light. • Improved performances, visible light addressability, quantum yield of photoisomerization, of oxindole based molecular motors compared to previously reported. Future applications of light-driven molecular motors in bio-based systems and soft materials require their operation with benign, low-energy light irradiation. Here we report four rotary molecular motors based on oxindole units which can be driven by near-infrared light. By installing an electron-withdrawing CN group on the oxindole lower half, in direct conjugation through the alkene axle to the electron-donating OMe substituent on the upper half, our design establishes a rigid push–pull system which red-shifts the absorption maximum further into the visible region. We also show that the induced nonlinearity to the system increases their two-photon absorption cross section, and the operation of oxindole based molecular motors with 800 nm light for the very first time. The motors prepared in this work show improved performance compared to previous oxindole based motors, e.g. visible light addressability up to 530 nm and 1.5-fold increase in quantum yields in both directions, whilst retaining their desirable qualities of easy synthesis and fast rotation speed. [ABSTRACT FROM AUTHOR]

The linear and nonlinear optical properties of two BODIPY derivatives, 1,7-Diphenyl-3,5-bis(9,9-dimethyl-9H-fluoren-2-yl)-boron-diuoride-azadipyrromethene (ZL-61) and 1,7-Diphenyl-3,5-bis(4-(1,2,2-triphenylvinyl)phenyl)-boron-diuoride-azadipyrromethene (ZL-22), were comprehensively investigated based on experimental and theoretical studies. It was found that both compounds show a strong two-photon absorption response in the near-infrared regime, and the two-photon-absorption cross-section values of ZL-61 and ZL-22 were determined to be 8321 GM and 1864 GM at 800 nm, respectively. The improvement of the two-photon absorption cross section in ZL-61 was attributed to the enhancement of the donor group, which was confirmed by transient absorption measurements and DFT calculation. Our results indicate that these BODIPY derivatives are a promising candidate for optical limiting and two-photon imaging applications. [ABSTRACT FROM AUTHOR]

Raman spectroscopy has proven useful for chemical agent detection, but the wavelength‐dependent scattering cross section and absorption, as well as induced fluorescence, usually affects the sensitivity. Ultraviolet (UV) wavelength excitation is investigated as a method to increase the efficiency and possibly enhance the applicability for detection of contamination on surfaces from a distance, potentially including an imaging capability. With this aim, we have measured UV Raman spectra and their strength as a function of laser wavelength in a range from 210 to 330 nm using a tunable pulsed laser and a response calibrated spectroscopic system. Results from small droplets of the low volatile chemical warfare agents, GA (tabun), GF (cyclosarin), sulfur mustard (HD), and the agent simulant tributyl phosphate (TBP) applied to silicon wafer surfaces are reported. Particular emphasis is put on the radiative ratio of observed Raman scattering to laser excitation, quantified as the Raman target efficiency. Measured absorption cross sections were used to estimate the effective optical depth and molecular Raman cross sections as a function of wavelength. In addition, a secondary optical probe and spectrometer were used to monitor any induced fluorescence. [ABSTRACT FROM AUTHOR]

In this paper, the scattering-to-absorption ratio that is a measurable factor and defined as the ratio of the scattering cross section to the absorption cross section in plasmonic core-shell nanoparticles with different shapes is investigated. The effect of various plasmonic materials on the scattering-to-absorption ratio is presented that can tune the plasmon resonance and play a key role in plasmonic solar cell efficiency improvement. In addition to using plasmonic materials as silver and gold, we use poor metals as bismuth because these types of metals are good materials for UV plasmonics. We also use semiconductor copper chloride (CuCl) in our calculations, because this material exhibits a strong exciton resonance, while the interaction between the plasmon resonance in metals and the exciton resonance in CuCl leads to new plexcitonic modes. [ABSTRACT FROM AUTHOR]

The incomplete absorption of the incoming light radiation in the absorber layer of the organic solar cell (OSC) is a major issue in OSC technology. Persistent research is being carried out to address this issue and the incorporation of metallic nanoparticles (MNPs) has been considered a viable option. The presence of MNPs in the active layer of the cell enhances the absorption of light, thereby leading to increased cell efficiencies. An effort has been made to critically evaluate the incorporation of spherical silver nanoparticles in the active layer of a Poly (3-hexylthiophene): phenyl-C61-butyric acid methyl ester (P3HT:PCBM) based OSC. The optical properties of the active layer are affected by the incorporated MNPs. The MNPs with their characteristic absorption and scattering cross section affect the absorption capabilities of the active layer absorber material. The absorption coefficient of the active layer also gets modified because of the presence of the MNPs in it. An analytical model is proposed to describe the effect of the changing sizes of the incorporated MNPs on the absorption coefficient and the ensuing generation of charge carriers in the OSC. The generation to recombination rate ratio (G/R) has been coined as a performance parameter for the quantification of the effect of the introduction of MNPs in OSCs. This parameter has not been used earlier for the performance analysis of the MNP-incorporated OSCs. [ABSTRACT FROM AUTHOR]

Light ion breakup cross sections are important for studies of cosmic ray interactions in the inter-stellar medium or radiation protection considerations of energy deposition in shielding and tissues. Abrasion cross sections for heavy ion reactions have been modeled using the Glauber model in the large mass limit or Eikonal form of the optical potential model. Here we formulate an abrasion model for 4He fragmentation on protons using the Glauber model avoiding the large mass limit and include a model for final state interactions. Calculations of energy dependent total, absorption, elastic and breakup cross sections for 4He into 3He or 3H with proton targets are shown to be in good agreement with experiments for energies from 100 to 100,000 MeV/u. The Glauber model for light nuclei with and without a large mass limit approximation is shown to be in fair agreement above 300 MeV/u, however important differences occur at lower energies. [ABSTRACT FROM AUTHOR]

Aerosol light absorption was measured during a 1-month field campaign in June–July 2019 at the Pallas Global Atmospheric Watch (GAW) station in northern Finland. Very low aerosol concentrations prevailed during the campaign, which posed a challenge for the instruments' detection capabilities. The campaign provided a real-world test for different absorption measurement techniques supporting the goals of the European Metrology Programme for Innovation and Research (EMPIR) Black Carbon (BC) project in developing aerosol absorption standard and reference methods. In this study we compare the results from five filter-based absorption techniques – aethalometer models AE31 and AE33, a particle soot absorption photometer (PSAP), a multi-angle absorption photometer (MAAP), and a continuous soot monitoring system (COSMOS) – and from one indirect technique called extinction minus scattering (EMS). The ability of the filter-based techniques was shown to be adequate to measure aerosol light absorption coefficients down to around 0.01 Mm-1 levels when data were averaged to 1–2 h. The hourly averaged atmospheric absorption measured by the reference MAAP was 0.09 Mm-1 (at a wavelength of 637 nm). When data were averaged for >1 h, the filter-based methods agreed to around 40 %. COSMOS systematically measured the lowest absorption coefficient values, which was expected due to the sample pre-treatment in the COSMOS inlet. PSAP showed the best linear correlation with MAAP (slope=0.95 , R2=0.78), followed by AE31 (slope=0.93). A scattering correction applied to PSAP data improved the data accuracy despite the added noise. However, at very high scattering values the correction led to an underestimation of the absorption. The AE31 data had the highest noise and the correlation with MAAP was the lowest (R2=0.65). Statistically the best linear correlations with MAAP were obtained for AE33 and COSMOS (R2 close to 1), but the biases at around the zero values led to slopes clearly below 1. The sample pre-treatment in the COSMOS instrument resulted in the lowest fitted slope. In contrast to the filter-based techniques, the indirect EMS method was not adequate to measure the low absorption values found at the Pallas site. The lowest absorption at which the EMS signal could be distinguished from the noise was >0.1 Mm-1 at 1–2 h averaging times. The mass absorption cross section (MAC) value measured at a range 0–0.3 Mm-1 was calculated using the MAAP and a single particle soot photometer (SP2), resulting in a MAC value of 16.0±5.7 m2g-1. Overall, our results demonstrate the challenges encountered in the aerosol absorption measurements in pristine environments and provide some useful guidelines for instrument selection and measurement practices. We highlight the need for a calibrated transfer standard for better inter-comparability of the absorption results. [ABSTRACT FROM AUTHOR]

• Absorption cross sections of SF 6 in mixtures with air complemented with explicit uncertainty calculation for every wavenumber. • Integrated intensities in the region of fundamental and combination bands in MIR with comparable uncertainty. • Comparison with ab initio values. We have obtained low-uncertainty absorption cross sections of sulfur hexafluoride (SF 6) in mixtures with synthetic air at 296 K in the mid-infrared region. An explicit uncertainty calculation for every wavenumber has been performed. The integrated intensities in the region of the two IR-active fundamental bands ν 3 and ν 4 were evaluated with expanded uncertainties below 1.2 %. Several combination bands, involving ν 3 , ν 4 and ν 5 fundamentals were also targeted. The integrated intensities higher than 10–19 cm/molec (transitions ν 2 + ν 4 , ν 1 + ν 3 , ν 2 + ν 3 and ν 5 + ν 6) were determined with uncertainties below 2.8 %. Data files are available online, doi: 10.7795/720.20231027. [Display omitted] [ABSTRACT FROM AUTHOR]

In this work, we developed a numerical method to investigate the effects of black carbon (BC) morphology on the estimation of brown carbon (BrC) absorption using the absorption Ångström exponent (AAE) methods. Pseudo measurements of the total absorption were generated based on several morphologically mixed BC models, then the BrC absorption was inferred based on different BC AAE methods. By investigating the estimated BrC absorption at different parameters, we have demonstrated under what conditions the AAE methods can provide good or bad estimations. As recent studies have shown that both externally and internally mixed BC still exhibits a relatively small fractal dimension value, the AAE = 1 method is still a reasonable method to estimate the BrC absorption as the AAE of fluffy BC does not deviate significantly from 1. However, the deviation between the "true" and the estimated BrC mass absorption cross section (MAC) should also be carefully considered as sometimes the MAC deviation estimated using the AAE = 1 method can reach a value that is comparable to the true BrC MAC for internally mixed particles. The Mie AAE method can just provide relatively reasonable estimations for small particles, and the BrC absorption deviations estimated using the Mie AAE methods are rather substantial for large particles. If the BC core still exhibits a fluffy structure, the deviation between the true and the estimated BrC MAC can reach 4.8 and 5.8 m 2 /g for large externally and internally mixed particles, respectively. Even for a compact BC core, the BrC MAC deviation estimated using the Mie AAE method can reach approximately 2.8 m 2 /g when the BC size is large. By comparing the AAE of spherical BC and detailed BC models, we found that the AAE does not deviate significantly from 1 if BC presents a fluffy fractal structure, while it varies considerably with particle size if BC exhibits a spherical structure, and the AAE value of spherical BC can vary from a negative value to approximately 1.4. The precalculated wavelength dependence of AAE (WDA) method does not necessarily improve the estimations. In many cases, the WDA method even provides a worse estimation than the BC AAE =1 and Mie AAE methods. Our results showed that the WDA does not deviate significantly from 0 if the BC core presents a fluffy structure, while the WDA of spherical BC can vary significantly as the particle size changes. The deviation between the true and the estimated BrC MAC using the WDA method can reach approximately 9 m 2 /g for externally mixed particles, which is far more than BrC MAC itself. As recent studies have shown that BC commonly exhibits a fluffy structure but not a spherical structure, the estimation of BrC absorption based on the AAE method should carefully consider the effects of BC morphologies. [ABSTRACT FROM AUTHOR]

We demonstrate the nonlinear saturable absorption effects of colloidal Au–CsPbBr3 inorganic nanocrystals (INCs) that may useful as a saturable absorber in passively mode-locked pulse lasers. Femtosecond open-aperture Z-scan technique is responsible for measuring the nonlinear saturable absorption effects at 800 nm with a repetition rate of 76 MHz and a laser pulse duration of 130 fs. Compared to colloidal pure-CsPbBr3 INCs, the nonlinear saturable absorption coefficient β ~ 2.34 × 10–10 cm/W and the second-order absorption cross section σ2 ~ 2.13 × 104 GM of colloidal Au–CsPbBr3 INCs can be improved by up to one order of magnitude at the Au-doping concentration of 3.5 mmol/L, thanks to an obviously cocked tail absorption from visible to near-infrared spectral region through the localized surface plasmon-induced charge transition at Au–CsPbBr3 INCs interface rather than the light scattering of the deposited Au nanoparticles. And the deposited Au nanoparticles have not changed the crystalline structure, stability, and morphology of colloidal pure-CsPbBr3 INCs. As a result, colloidal Au–CsPbBr3 INCs are expected to become a potential saturable absorption candidate material used in passively mode-locked pulse lasers. [ABSTRACT FROM AUTHOR]

Black holes are among the most intriguing objects in nature. They are believed to be fully described by General Relativity (GR), and the astrophysical black holes are expected to belong to the Kerr family, obeying the no-hair theorems. Alternative theories of gravity or parameterized deviations of GR allow black hole solutions, which have additional parameters other than mass and angular momentum. We analyze a Schwarzschild-like metric, proposed by Johannsen and Psaltis, characterized by its mass and a deformation parameter. We compute the absorption cross section of massless scalar waves for different values of this deformation parameter and compare it with the corresponding scalar absorption cross section of the Schwarzschild black hole. We also present analytical approximations for the absorption cross section in the high-frequency regime. We check the consistence of our results comparing the numerical and analytical approaches, finding excellent agreement. [ABSTRACT FROM AUTHOR]

The human body absorption cross section (ACS) is important in nonionizing radiation dosimetry, but it is always hard to accurately evaluate the ACS of an individual from his or her morphological parameters, such as height and weight. To obtain an empirical formula that can evaluate the ACS from morphological parameters, 48 subjects with different morphological parameters were measured from 1 to 16 GHz in a reverberation chamber. The ACS was extracted from the power delay profile. This has the advantage of not requiring antenna radiation efficiency, and it has not been previously used in a wideband group study like this. The accuracy of the ACS measurement is demonstrated by comparison with the ACS of a spherical model with known structure and material, and the mean absolute percentage error of the sphere measurement is just 3.4%. Statistical analysis shows that the body surface area (BSA) has the strongest correlation with the ACS among all the morphological parameters; therefore, we present a new empirical ACS formula as a function of BSA and frequency. This will be of interest to those considering dosimetry, and in computing the effect of human body absorption on radio propagation in vehicles and other structures. [ABSTRACT FROM AUTHOR]

In this work we present a novel two-color differential absorption diagnostic near 5.6 μ m using an external-cavity quantum-cascade-laser (EC-QCL) for formaldehyde (CH 2 O) detection in high-temperature reacting gases. This diagnostic utilizes the narrow mid-infrared absorption features of CH 2 O in the R branch of the C=O stretching band. Specifically, the online and offline colors were chosen as 1787.05 cm-1 and 1787.85 cm-1, respectively. Compared to the previous Stanford work that targeted the 3.5 μ m band of CH 2 O, this new diagnostic achieved higher sensitivity, better species selectivity and immunity to interference absorption from other combustion gases, especially small hydrocarbons (e.g. methane). Absorption cross sections of CH 2 O at the two colors were measured in shock-heated 1,3,5-trioxane/argon mixtures over a wide range of temperatures and pressures: 870 K ≤ T ≤ 1800 K, 0.7 atm ≤ P ≤ 4.5 atm. These cross section measurements were further expressed as analytical functions of temperature and pressure with 2 σ statistical uncertainties of ± 4.9%. Initial application of the diagnostic was demonstrated in a shock tube study of the thermal decomposition of methanol/argon mixture at 1427 K and 2.77 atm, where the measured CH 2 O time-history was compared with simulations from multiple combustion mechanisms. We expect this new diagnostic to be useful in future combustion studies. [ABSTRACT FROM AUTHOR]

The C 1B2-X 1A1 photoexcitation of SO2 was studied to investigate excited-state dynamics and the effects of the initial vibrational state. Ultraviolet photoabsorption cross sections (σ's) of seven isotopologues (32S 16O2, 33S 16O2, 34S 16O2, 36S 16O2, 32S16O17O, 32S16O18O, 34S16O18O) were computed using the wave packet propagation technique based on the three-dimensional potential energy surfaces of the X and C states, which were calculated using the ab initio molecular orbital configuration interaction method. Numerous wave packet simulations were carried out under the adiabatic approximation and used to calculate the σ’s of the seven isotopologues at 298 K; we concluded that the absorption spectrum of SO2 can be reliably modeled within the adiabatic framework based on the analysis of the time evolution of the wave packet. The calculated σ’s are in reasonable agreement with the recent experiment in the 190–228 nm region, and the isotope shifts of the peaks for 33S 16O2 and 34S 16O2 relative to the corresponding peaks for 32S 16O2 are in good agreement with the observed data. Relative to the σ of 32S 16O2, isotopic substitution shows a significant increment for those of 34S 16O2 and 36S 16O2 in the 190–228 nm region. This trend is consistent with the observed data. [ABSTRACT FROM AUTHOR]

We have studied the basis set and electron correlation effects on the ab initio calculations of two-photon absorption cross sections of water. Various series of correlation consistent basis sets up to triply augmented basis sets of valence pentuple ζ level as well as the popular 6-31G(d) basis set have been employed in combination with several coupled cluster, configuration interaction, and density functional theory methods. We find that it is very difficult to obtain converged values of the cross sections for even a small molecule such as water. Acknowledging these difficulties in obtaining a fully converged cross section for a given state, we also investigated the possibility of determining relative cross sections for a series of organic molecules. However, we did not find consistency between the relative cross sections calculated at the Hartree-Fock level and several coupled-cluster methods using the 6-31G(d) and aug-cc-pVDZ basis sets. However, we could reproduce the relative ordering of the two-photon absorption cross sections of the molecules studied at the Hartree-Fock level. [ABSTRACT FROM AUTHOR]

• Two-layer spheroid is considered as a model of compound black carbon aerosols. • Numerical modeling of scattering properties is performed for soot-sulfate spheroids. • Behavior of calculated scattering and absorption characteristics is analyzed. We analyze the results of numerically exact modeling of scattering and absorption characteristics of randomly oriented polydisperse spheroidal soot particles covered by spheroidal nonabsorbing sulfate shell. Using numerically exact T -matrix method, at wavelengths 0.355 μm, 0.532 μm and 1.064 μm, we perform computations of the absorption cross section (C abs), absorption Ångström exponent (AAE), backscattering linear depolarization ratio (LDR) and scattering matrix elements for spheroids with core volume-equal-sphere effective radius (further in the text, the term "effective radius" is used) R c,eff = 0.1, 0.15 μm, soot volume fraction. f = 7% and 15%. Mostly, we consider the case of oblate spheroids with the axis ratio ε ranging from 1.1 to 1.8. Our size-averaged results demonstrate, in particular, that: (i) the absorption cross section depends on the degree of nonsphericity very weakly, but substantially increases with increasing aerosol size and decreases with increasing wavelength; (ii) the absorption Ångström exponent also shows a weak dependence on the spheroid axis ratio, but it is quite sensitive to the choice of the wavelength pair, particle size and amount of soot/sulfate; (iii) the backscattering linear depolarization ratio is very sensitive to particle nonsphericity, size, amount of sulfate coating and wavelength, and concentric soot-sulfate spheroidal particles could cause a wide range of the LDR values that significantly decrease with increasing wavelength. We also conclude that at backscattering angles, the elements of the normalized scattering matrix exhibit specific changes which depend on particle shape, size, and amount of coating material. [ABSTRACT FROM AUTHOR]

[Display omitted] Cross section of the two-photon absorption in 7-dialkylamino-3-(3-pyrazolinyl)coumarins in acetone and polymethylmethacrylate films has been found to be dependent on the substrate and medium nature. 7-Dialkylamino-3-[1,5-diaryl(3-pyrazolinyl)]coumarins are shown to be effective in the photosensitive media with excitation at 1060 nm for optical recording of information. [ABSTRACT FROM AUTHOR]

The physical properties of black carbon (BC) including the mass loading, size distribution and mixing state were in-situ characterized by aircraft measurements using a single particle soot photometer (SP2) in the lower troposphere over Beijing area. The flights were conducted in both late spring and winter during the daytime with well-developed planetary boundary layer (PBL). The BC mass in the PBL (BC PBL) in late spring showed no apparent vertical gradient nor correlation with the PBL height (PBLH) due to strong convective mixing; in winter the BC PBL was more concentrated near ground and anti-correlated with the PBLH due to dilution effect of the dominant cleaner northerly air masses at higher altitude. The BC mass loading at height h , C(h) within the PBL can be extended from the surface level (C0) in late spring; for levels above the PBL, C(h) can be parameterized by applying an exponential decline function C(h) = C0*exp(h/hs) , with the scale height (hs) of 0.31 ± 0.16 km and 0.66 ± 0.24 km for late spring and winter respectively. This parameterization excluded the profiles for: turbulent conditions when the BC mass was efficiently vented upwards and diluted, expressed as C(h) = C0 up to the top of the PBL; or in periods of strong southerly advection, when the entire column was significantly influenced by regional transport from the polluted south regions. The BC core mass median diameters (MMD) were commonly populated at 205–220 nm in both seasons, with additional mode of MMD ∼195 nm also frequently observed in late spring. The bulk relative coating thickness of BC (coated diameter divided by uncoated core diameter D p /D c) in the PBL mostly populated at 2.0–2.2 but at ∼1.2–1.6 in the lower free troposphere (FT). The mass absorption cross section of BC at 550 nm (MAC550), constrained by the SP2 measurements, was largely influenced by the coating thickness, was relatively consistent in the PBL at ∼8.6 m2 g−1, but reduced to 7–7.5 m2 g−1 in the FT or turbulent condition due to decreased coatings. The BC was found to exhibit smaller particle size in the FT but larger in the PBL, which may imply larger BC have been scavenged by low-level clouds. The BC particles trapped in the PBL or regionally transported from polluted region represent the most absorbing element in the particulate matter population and should be particularly considered in evaluating the radiative forcing impact of aerosols over this region. • Vertical profiles of black carbon physical properties in the lower troposphere were in-situ characterized over Beijing. • Black carbon at different layers was influenced by seasonal emission and meteorological conditions. • These results will improve modelling on black carbon radiative forcing and constrain remote sensing absorption measurement. [ABSTRACT FROM AUTHOR]

Studies the photoabsorption cross section of small sodium and lithium clusters using time-dependent local density approximation to density functional theory. Types of ab initio nonlocal pseudopotentials; Equilibrium geometries of the clusters obtained via Langevin quantum molecular dynamics; Average bond length of the clusters.

The femtosecond pulsed Z-scan measurements of the resonant nonlinear optical absorption of the InN epitaxial films in the range of 720–790 nm were reported. The absorption saturation behavior was found to gradually decrease with increasing photon energy. The nonlinear optical absorption cross sections of the InN films were estimated and the values are found to be in good agreement with the calculations based on the band-filling model. These results are relevant for the future development of nonlinear optical devices based on InN. [ABSTRACT FROM AUTHOR]

Given potential applications of multiphoton absorbers, in the present work we have studied the symmetry-relaxation effects in one- and two-photon absorption spectra in two bichromophore systems based on difluoroborate core linked by biphenylene or bianthracene moieties. We have employed a palette of experimental methods (synthesis, one- and two-photon spectroscopy, X-ray crystallography) and state-of-the-art computational methods to shed light on how symmetry relaxation, a result of twisting of building blocks, affects one- and two-photon absorption of the two studied fluorescent dyes. Electronic-structure calculations revealed that the planarity of central biphenyl moiety, as well as deviations from planarity up to 30–40 deg., ensure maximum values of two-photon transition strengths. Perpendicular arrangement of phenylene units in biphenylene moiety leads to 20% drop in the two-photon transition strengths. More detailed studies demonstrated that equilibrium structures of both compounds in chloroform solution show very different values of two-photon absorption cross sections at absorption band maxima, i.e. 224 GM for and 134 GM for biphenyle and bianthracene linkers, respectively. The latter value is in good agreement with experimental value obtained using Z-scan method. The difference in two-photon absorption cross section between both compounds can be rationalized based on equilibrium geometry differences, i.e. interplanar angle is 35 deg and 91 deg in the case of biphenylene and bianthracene moiety, respectively. It is thus not beneficial to introduce conformationally locked central linker based on bianthracene moiety. [Display omitted] • Two-photon absorption of biphenylene- and bianthracene-based bichromophores is studied. • Symmetry plays a key role in two-photon response of studied bichromophores. • Bianthracene-based bichromophore is less efficient two-photon absorber. [ABSTRACT FROM AUTHOR]

In this work, we report first-principle theoretical predictions of methane spectral line intensities that are competitive with (and complementary to) the best laboratory measurements. A detailed comparison with the most accurate data shows that discrepancies in integrated polyad intensities are in the range of 0.4%–2.3%. This corresponds to estimations of the best available accuracy in laboratory Fourier Transform spectra measurements for this quantity. For relatively isolated strong lines the individual intensity deviations are in the same range. A comparison with the most precise laser measurements of the multiplet intensities in the 2ν 3 band gives an agreement within the experimental error margins (about 1%). This is achieved for the first time for five-atomic molecules. In the Supplementary Material we provide the lists of theoretical intensities at 269 K for over 5000 strongest transitions in the range below 6166 cm −1 . The advantage of the described method is that this offers a possibility to generate fully assigned exhaustive line lists at various temperature conditions. Extensive calculations up to 12,000 cm −1 including high-T predictions will be made freely available through the TheoReTS information system (http://theorets.univ-reims.fr, http://theorets.tsu.ru) that contains ab initio born line lists and provides a user-friendly graphical interface for a fast simulation of the absorption cross-sections and radiance. [ABSTRACT FROM AUTHOR]

Determination of the distribution of electromagnetic energy inside electrically large enclosed spaces is important in many electromagnetic compatibility applications, such as certification of aircraft and equipment shielding enclosures. The field inside such enclosed environments contains a dominant diffuse component due to multiple randomizing reflections from the enclosing surfaces. The power balance technique has been widely applied to the analysis of such problems; however, it is unable to account for the inhomogeneities in the field that arise when the absorption in the walls and contents of the enclosure is significant. In this paper, we show how a diffusion equation approach can be applied to modeling diffuse electromagnetic fields and evaluate its potential for use in electromagnetic compatibility applications. Two canonical examples were investigated: a loaded cavity and two cavities coupled by a large aperture. The predictions of the diffusion model were compared to measurement data and found to be in good agreement. The diffusion model has a very low computational cost compared to other applicable techniques, such as full-wave simulation and ray-tracing, offering the potential for a radical increase in the efficiency of the solution high frequency electromagnetic shielding problems with complex topologies. [ABSTRACT FROM PUBLISHER]

In this study, we provide a novel approach for exposure assessment in terms of whole-body average specific absorption rate (WBSAR) due to the electromagnetic fields inside reverberant environments. The approach utilizes power balance theory and the lossy object's absorption cross section ( ACS). We use this to present a noninvasive technique for determining the WBSAR in reflective environments. Measurements were performed inside a reverberation chamber on spherically-shaped phantoms filled with lossy liquids. The approach was verified by performing invasive temperature measurements and showed excellent agreement (within 5%). This approach can be used for human exposure assessment inside reverberant environments since human body ACS has been well studied in the literature. The main advantage of the proposed approach is that it overcomes the need for complex invasive measurements in order to determine WBSAR. [ABSTRACT FROM PUBLISHER]

Multi-cell thin-walled structures have recently gained attentions in aerospace and automotive industries for their excellent energy absorption capacity with lightweight. This paper introduces a novel 3D-multi-cell design to enhance energy absorption capability of multi-cell thin-walled tubes by performing a new arrangement of the internal webs and dividing them into multilayers with different angles of orientation. A comparative study of energy-absorbing performance of single-cell, conventional multi-cell and the proposed three-dimensional multi-cell (3D-multi-cell) of thin-walled circular tubes under axial impact loading is carried out using the non-linear finite element code ANSYS-WORKBENCH/LS-DYNA. The numerical results show that the 3D-multi-cell configuration can achieve a significant improvement in the energy absorption per unit mass (SEA) up to 40%, the crush force efficiency (CFE) up to 42.5%, and the energy absorption effectiveness factor (ψ) up to 30.7% in comparison with those of circular tube. Furthermore, it can significantly improve the SEA up to 20%, the CFE up to 36.8%, and the ψ up to 20% in comparison with those of conventional multi-cell configuration. Furthermore, it is found that the number of layers and angle of orientations have a distinctive effect on the energy absorption capacity and the CFE. [ABSTRACT FROM PUBLISHER]

It is shown in this letter that the average absorption coefficient (AAC) of an object under test (OUT) can be obtained by comparing the measured absorption cross section (ACS) of the OUT with the ACS value of a perfect absorber of the same shape. The ACS of an arbitrarily shaped electrically large perfect absorber can be obtained numerically. Measurements are performed to demonstrate the proposed method. Results show that the AAC is not sensitive (but not independent) to the shape and size of an electrically large absorber. The procedure proposed in this letter can be used to characterize the electromagnetic wave absorptive and scattering ability of arbitrarily shaped objects. A system-level AAC could be very useful for many applications. [ABSTRACT FROM PUBLISHER]

Absorption by the contents of an equipment enclosure, particularly printed circuit boards (PCBs), affect the enclosure's shielding performance. At high frequencies, this absorption can be quantified using the angle of arrival and polarization averaged absorption cross-section (ACS). However, there is no available data on the high-frequency absorption characteristics of modern PCBs. In this study, we apply a reverberation chamber to the determination of the average ACS of a large number of PCBs taken from contemporary information and communication technology (ICT) equipment to provide a unique and comprehensive dataset. The ACS was found to range from 4 × 10−4–10−2 m2 from 2–20 GHz and different classes of PCB could be identified according to their surface characteristics. The “shadowing effect” of densely packed PCBs was also quantified for a subset of the PCBs. It was found that the ACS of a PCB in the stack was reduced by 20%–40% compared to its value when isolated. By way of a review of the general power balance analysis of an electrically large populated equipment enclosure in an external environment, we show how the acquired data will be useful for future qualification methodologies for ICT enclosures and PCBs. [ABSTRACT FROM PUBLISHER]

In the present work, the one- and two-photon absorption cross section of fluorescent substituted polyaryl pyridine-based compounds was investigated. We show that the two-photon cross section is enhanced when the electron donor and acceptor groups are coplanar. [Display omitted] • The one- and two-photon parameters of new pyridine-based compounds are proposed. • The relations between structures and one- and two-photon absorption cross-section is highlighted. • The two-photon absorption in these compounds is a two states process. • The two-photon is driven by charge transfer mechanism. • The two-photon cross-section is enhance by the presence of electron donor and acceptor groups in a parallel plan. In this work, the one- and two- photon absorption of polyaryl substituted pyridine were investigated theoretically. The considered compounds have been reported in a previous work to be of appreciable fluorescence quantum yield in the visible domain. Herein, their two-photon absorption cross section at the maximum linear absorption wavelength was found to be ranged between 20 and 250GM, conferring to these compounds moderate to strong two-photon activity. Two-photon absorption cross section was enhanced by the presence of electrons donor (ED) and acceptor (EW) groups, positioned in the same plan and branched to the pyridine in a linear ED-pi-EW configuration. We found by considering the MOs involved in the linear absorption that, the nonlinear absorption in the considered pyridines was a two states process, governed by intramolecular-charge transfer excitation. These compounds can serve as starting structure for the designing of new molecular probes for environment sensing based on two-photon absorption process. [ABSTRACT FROM AUTHOR]

The measurement of the absorption cross section (ACS) is one of the applications of a reverberation chamber. In this letter, a statistical analysis of the uncertainty of ACS measurements is shown. The achieved model enhances the one already present in the literature and is done differently. Measurements show the importance of the uncertainty component connected to the position of the antennas and/or of the absorbing sample and how it is reduced so that the simple model based only on independent samples can be effectively used. [ABSTRACT FROM AUTHOR]

An original experimental protocol is developed to assess the whole-body absorption cross section of objects with arbitrary shapes and materials in diffuse fields at any operating frequency. This approach is important for dosimetry specifically in realistic environments wherein diffuse fields can be prominent. For this application, the knowledge of the whole-body specific absorption rate is critical and can be determined from the human whole-body absorption cross section. The whole-body absorption cross section is obtained from measurements performed in a stirred-mode reverberating chamber processed with the high-resolution parameter estimator RiMAX. To validate the proposed approach and highlight its robustness, the whole-body absorption cross section of a cylindrical phantom is experimentally and numerically determined at 1800 MHz. For both methods, the whole-body absorption cross section is shown to be independent on the orientation of the transceivers, indicating that it is indeed caused by diffuse fields. A good agreement is obtained between experimental and numerical finite-difference time-domain results with a relative deviation of about 17%. From the validation of this approach, the measurement protocol is applied to a real human at 1800 MHz resulting in a whole-body absorption cross section of 0.95 m ^2, 1.01 m^2 , and 1.11 m^2 for a sitting, standing, and standing with stretched arms posture, respectively. [ABSTRACT FROM PUBLISHER]

We present broadband reverberation chamber measurements of the absorption cross section (ACS) of the human body averaged over all directions of incidence and angles of polarization. This frequency-dependent parameter characterizes the interactions between the body and the enclosures of reverberant environments such as aircraft cabins, and is, therefore, important for the determination of the overall Q-factor and, hence, the field strength illuminating equipment inside such enclosures. It also correlates directly with the electromagnetic exposure of occupants of reverberant environments. The average ACS of nine subjects was measured at frequencies over the range 1–8.5 GHz. For a 75-kg male, the ACS varied between 0.18 and 0.45 square meters over this range. ACS also correlated with body surface area for the subjects tested. The results agree well with computational electromagnetic simulations, but are obtained much more rapidly. We have used the obtained values of ACS to estimate the effect of passengers on the Q-factor of a typical airliner cabin. [ABSTRACT FROM PUBLISHER]

Pyrazine-decorated benzotriazole cores allow the orthogonal combination of two dipolar systems within a single molecule. A series of this type of derivatives was synthesized and their photophysical features were studied. The properties of these compounds showed remarkable differences in function depending on the substitution in the pyrazine ring of the benzotriazole core. Furthermore, the two-photon absorption property (2PA) was studied to determine the structure-properties relationship for the reported compounds. The best dye achieved a cross-section of 1532 GM, which was higher than values previously obtained for similar D-π-A-π-D benzotriazole derivatives. TD-DFT calculations, which supported the experimental observations, indicating the interaction between the two dipolar systems was responsible for enhancing the 2 PA properties and favoring bathochromic shifts. [Display omitted] • Five pyrazine-decorated benzotriazole derivatives have been prepared and fully characterized. • These dyes have tunable positions yielding orthogonal combination of two dipolar systems within a unique alkynyl-TzQ core. • One- and two-photon photophysical characterizations were done showing two-photon absorption cross sections up to 1532GM. • The DFT and TD-DFT calculations have been used to interpret the experimental results. [ABSTRACT FROM AUTHOR]

Abstract: Complex refractive index for submicron absorbing spheres was determined by simultaneously measuring absorption coefficients and number concentrations with a multiangle absorption photometer and a condensation particle counter, respectively. The absorption cross section calculated from the absorption coefficient and the number concentration was fitted to the absorption cross section calculated using Mie theory. For homogeneously dyed spheres, the absorption cross section depended on the size of sphere. For non-homogeneously dyed spheres, however, the absorption cross section had nothing to do with the size of sphere. It is concluded that the ability to measure refractive index by our method held good as long as the absorption phenomenon takes place in the near field surrounding particles surface. To the best of our knowledge, it is for the first time that the refractive index was determined by only absorption measurements and theory. This method is believed to help understand the fundamental of the optical properties for other absorbing particles. [Copyright &y& Elsevier]

A coastal Roseobacter strain of marine aerobic anoxygenic phototrophic bacteria (AAnPB) was isolated and phylogenetically determined. The strain OBYS 0001 was characterized by its physiological and biochemical properties with reference to the Erythrobacter longus type strain NBRC 14126. When grown in batch cultures, the growth curves of the both strains were similar. Cellular bacteriochlorophyll a concentrations of the strains reached the maxima in the stationary growth conditions. In vivo fluorescence excitation/optical density spectra between 470 and 600 nm for OBYS 0001 represented higher values than NBRC 14126. Variable fluorescence measurements revealed that the functional absorption cross section (σ) of the bacterial photosynthetic complexes for OBYS 0001 was significantly higher than that for NBRC 14126 under green excitation. These results suggest that Roseobacter can capture green light more efficiently than Erythrobacter for photosynthesis. The photochemical quantum efficiencies ( F/ F) of the bacterial photosynthetic complexes for OBYS 0001 were consistently lower than those for NBRC 14126. A relationship between the growth rate and F/ F was significant for OBYS 0001, but that was not found for NBRC 14126. These results suggested that F/ F for AAnPB could not be used as a proxy of the growth rate which is consistent with their mostly heterotrophic characters. [ABSTRACT FROM AUTHOR]

The optimal filling of the intermediate band (IB) of an IB solar cell is investigated. Using models based on detailed balance principles, it is shown that the optimal filling varies with the size of the subband gaps, the absorptivity of the cell, and the degree of the overlap between the absorption coefficients as well as the mutual sizes of the absorption cross sections for transitions over the subband gaps. The results of calculations that show how nonoptimal filling affects the cell efficiency are also presented. In several cases, a deviation from the optimal filling will only result in small changes in the efficiency. However, cases where the efficiency is reduced dramatically due to nonoptimal filling are also identified. For some cases, the negative impact of nonoptimal filling can be reduced by increasing the absorptivity of the cell or, when the effect of photofilling is significant, by increasing the light concentration. [ABSTRACT FROM AUTHOR]

Abstract: The level of “anomalous” charmonium suppression in high-energy heavy-ion collisions and its interpretation as a signal of quark-gluon plasma formation requires a robust understanding of charmonium production and absorption in proton-nucleus collisions. In a previous study we have shown that, contrary to common belief, the so-called “absorption cross section”, , is not a “universal constant” but, rather, an effective parameter that depends very significantly on the charmonium rapidity and on the collision energy. Here we present ugraded Glauber calculations with the EPS09 parameterization of nuclear modifications of the parton densities. We confirm that the effective “absorption cross section” depends on the kinematics and the collision energy. We also make further steps towards understanding the physics of the mechanisms behind the observed “cold nuclear matter” effects. [Copyright &y& Elsevier]

We have measured the polarized visible and near-infrared, and unpolarized mid-infrared (2.7 \mum) emission spectra of photorefractive-damage-resistant locally Er-Mg-doped near-stoichiometric (NS) Ti:Mg:Er:LiNbO3 strip waveguide, fabricated on an X-cut initially congruent LiNbO3 substrate in sequence by local Er doping in air, Mg-Ti pre-diffusion in wet O2 and post Li-rich vapor transport equilibration treatment. From the measured emission spectra, the emission and absorption cross section spectra were calculated based upon McCumber theory. The spectroscopic features are discussed in comparison with the spectra recorded from the area outside the waveguide, and with the previously reported results of bulk-doped NS Er:Mg:LiNbO3 crystals and congruent Er:LiNbO3 bulk material or Ti:Er:LiNbO3 waveguide structure. The results show that the spectra of the NS waveguide are traditional and reveal small differences from those spectra outside the waveguide in spectral shape, polarization dependence, as well as cross section values. In contrast, the cross section values of the NS waveguide show considerable differences from those of bulk-doped NS material and congruent bulk material or waveguide structure. The 552, 673, 996, and 1531 nm emission lifetimes of the Er^3+ ions outside the waveguide were also measured, and found to be comparable to the results of the bulk-doped NS crystal and the congruent bulk material or waveguide structure. [ABSTRACT FROM PUBLISHER]

Bridging the triindole core and triarylboryl acceptor by an ethenylene linker at the 3,8,13- or 2,7,12-position, the resultant 3-BETand 2-BETshow two-photon absorption (TPA) cross sections of δ = 2100 and 2500 GM (at 810 nm by femtosecond pulses in THF), respectively. The TPA enhancement of the 2,7,12-isomers is also found when comparing 3-BYTand 2-BYT(δ = 870 and 1900 GM) and 3-NETand 2-NET(36 and 400 GM). [ABSTRACT FROM AUTHOR]

Abstract: For the regime of strong size quantization, we perform theoretical investigation of electronic states and interband dipole transition in a narrow-gap InSb cylindrical layer quantum dot under the influence of both magnetic and electric field. The energy for the system under consideration is proportional to the magnetic field under square root, unlike the case of parabolic dispersion law. We consider the transition from the light hole and heavy hole states to the electron state of conduction band. In the plane of quantum dot cross section, the electronic states were approximated with the two-dimensional rotator model. The interband absorption coefficient and threshold frequencies for different electric field orientation in the presence of magnetic field were calculated and the selection rules are found. It is found that the electric field changes the selection rules. [Copyright &y& Elsevier]

Abstract: The two-photon absorption (TPA) properties of 4,4′-bis(para-di-n-butylaminostyryl)-2,2′-bipyridine (NBu2bipy) and related dipolar ([ZnY2(NBu2bipy)] (Y=Cl, CF3CO2), [Zn(2,2′-bipyridine)2(NBu2bipy)][PF6]2) and octupolar ([Zn(NBu2bipy)3][PF6]2) complexes were investigated by the two-photon emission (TPE) technique in a femtosecond regime, working in the 730–930nm spectral range. We found, in contrast with previous literature data, that the TPA enhancement upon coordination of a TPA active ligand to a metal center may be larger in the dipolar rather than the corresponding octupolar complex, the response being easily modulated by the choice of the ancillary ligands. [Copyright &y& Elsevier]

Abstract: Materials with large two-photon absorption (TPA) capability are highly useful not only for optical power limiting, but also for laser pulses’ stabilization in an optical communication system. A novel dipyrromethene boron difluoride (BODIPY) chromophore was synthesized and its TPA characteristic was investigated by the direct nonlinear transmission method in femto-second regime. This chromophore was found to have a broad TPA spectral distribution in the near-IR range, and a fairly large TPA cross-section of 101GM at around 1310nm. Using the BODIPY chromophore, both good optical limiting and optical stabilization performances were achieved at the wavelength of 1310nm. [Copyright &y& Elsevier]