Long-wave Band Research Articles

Photoluminescence of the ZnSe single crystals doped by thermal diffusion of nitrogen

Abstract Photoluminescence (PL) spectra of ZnSe single crystals annealed in different ambients containing molecular nitrogen are investigated. The compensating activity of N impurity in n-ZnSe crystals is shown. It is caused by the formation of N Se acceptor centers, having 101–108 meV activation energy. The intensity of amplification of both long-wave luminescence spectra bands and the edge luminescence spectra bands caused by the presence of nitrogen in annealing medium is investigated. The presented results allow one to assign the long-wave luminescence to deep acceptors caused by uncontrollable impurities, and the relevant bands of the edge luminescence spectra to the excitons bound with the same deep acceptors. The model explaining the transformations of the luminescent properties of ZnSe crystals by means of nitrogen impurity doping is proposed. The model considers the presence of donors having 75 meV activation energy, acceptors having 220–720 meV activation energy and centers having levels localized near the middle of the band gap.

Recoordination of a metal ion in the cavity of a crown compound: a theoretical study

The absorption spectra of styrylbenzothiazolium dye derivatives were calculated by the time-dependent density functional (TD DFT) method. The dyes of interest were (p-dimethylamino)styrylbenzothiazolium dye and its protonated form as well as aza-15(18)-crown-5(6)-containing dyes and their complexes with alkali (K+ and Na+) and alkaline-earth (Ca2+, Sr2+, and Ba2+) cations. Several low-lying conformers of the azacrown-containing dyes were considered. The electronic and geometric structures of the excited states responsible for the appearance of the long-wave (π-π*) absorption bands are studied. Complexation causes a hypsochromic shift of the long-wave absorption band correlating with the pyramidality of the crown ether nitrogen in the complex. The interaction of the cation with 3–4 solvent molecules or a counterion (ClO4−) considerably reduces this shift, especially in the conformers without the metal-nitrogen bond. In some cases, the long-wave absorption band is close to the absorption band of the free dye. Similar results were obtained using the polarizable continuum model of solvation. Excited-state structures of the free model dye and the free azacrown-containing dyes exhibit a tendency to bond alternation. Conversely, the cationic complexes of the crown-containing dyes and the protonated model dye exhibit a tendency to bond equalization in the excited state. The changes in the excited-state geometries of the free dyes and their complexes account for the complexation-induced fluorescence enhancement observed in the experiments.

Phthalocyanines and related compounds: XLVII. Nucleophilic replacement of chlorine atoms in tetrachlorophthalonitrile. Synthesis of phenyl(alkyl)amino-substituted phthalonitriles and some phthalocyanines based thereon

Nucleophilic replacement of chlorine atoms in tetrachlorophthalonitrile by the action of primary and secondary amines was studied. The reactions of tetrachlorophthalonitrile with amines at a ratio of 1: 10 gave with high yields and regioselectivity the corresponding 4,5-diamino-3,6-dichlorophthalonitriles from cyclic secondary amines and 4-amino-3,5,6-trichlorophthalonitriles from primary amines and acyclic secondary amines. 4-Amino-3,5,6-trichlorophthalonitriles were used to synthesize cobalt and zinc phthalocyanine complexes. It was shown that replacement of chlorine atoms in the pyrrolic β-positions of hexadecachlorophthalocyanines by amino groups is not accompanied by red shift of the long-wave absorption band in the electronic spectra.

Voltage-Tunable Two-Color Corrugated-QWIP Focal Plane Arrays

We demonstrated a 256 times 256 voltage-tunable two- color corrugated quantum-well infrared-photodetector focal plane array. The detector operation is based on photocurrent asymmetry in a double-superlattice quantum well structure. By using a broadband corrugated light coupling scheme, we obtained a quantum efficiency of 24% in the mid-wave (MW) band and 26% in the long-wave (LW) band without AR coating. Operating at 50 K, the measured noise equivalent temperature difference is 27 mK at 33-ms integration time for the MW and 90 mK at 2 ms for the LW with f/2.44 optics. The NETD operability values are 98.4% and 95.9%, respectively.

Spectroscopic and electrochemical properties of cyclopalladated complexes of 2,3-diphenylquinoxaline and 2,2′,3,3′-tetraphenyl-6,6′-biquinoline

Comparative study of cyclopalladated ethylenediamine complexes of 2,3-diphenylquinoxaline (Hdphqx) [Pd(dphqx)En]ClO4 and 2,2′,3,3′-tetraphenylbiquinoline (H2tphbq) [(PdEn)2(μ-tphbq)](ClO4)2, and the free heterocyclic ligands was performed by means of 1H NMR spectroscopy, electronic absorption and emission spectroscopy, and cyclic voltammetry. It was shown that cyclopalladation gives rise to a long-wave absorption band in the visible spectrum, a batochromic shift of the vibrationally structured phosphorescence band, and an anodic shift of the ligand-centered reduction potential of the complexes com-pared to free ligands.

Fluorescence spectrum characteristic of ethanol–water excimer and mechanism of resonance energy transfer

The steady-state fluorescence spectrum characteristic of ethanol–water excimer has been studied in this paper. By analysing the features of the sharp emission spectrum with fine structures in a shortwave band and the characteristics of the broad and featureless fluorescence peaks in the longwave band, one can conclude that the excimers are formed between the new ethanol–water cluster molecules in the excited state and the ground state through the interaction among different chromophores. The excitation spectra in the two fluorescence bands have been studied, and their emission mechanisms have been ascertained based on the energy transfer theory. Furthermore, the critical distance of the resonance energy transfer has been calculated.

Sensitivity of surface radiation budget to clouds over the Asian monsoon region

Using the ISCCP-FD surface radiative flux data for the summer season (June to September) of the period 1992 to 1995, an analysis was done to understand the role of clouds on the surface radiation budget over the Asian monsoon region. At the top of atmosphere (TOA) of convective regions of the Asian monsoon region, the short wave radiative forcing (SWCRF) and long wave radiative forcing (LWCRF) do not cancel each other resulting in occurrence of the net cloud radiative forcing values exceeding −30 W/m2. This type of imbalance between SWCRF and LWCRF at TOA is reflected down on the earth surface-atmosphere system also as an imbalance between surface netcloud radiative forcing (NETCRF) and atmospheric NETCRF.Based on the regression analysis of the cloud effects on the surface radiation budget quantities, it has been observed that generally, the variance explained by multiple type cloud data is 50% more than that of total cloud cover alone. In case of SWCRF, the total cloud cover can explain about 3% (7%) of the variance whereas the three cloud type descriptions of clouds can explain about 44% (42%) of the variance over oceanic (land) regions. This highlights the importance of cloud type information in explaining the variations of surface radiation budget. It has been observed that the clouds produce more cooling effect in short-wave band than the warming effect in long-wave band resulting in a net cooling at the surface. Over the oceanic region, variations in high cloud amount contribute more to variations in SWCRF while over land regions both middle and high cloud variations make substantial contributions to the variations in both SWCRF and NETCRF.

An investigation of the sensitivity of the clear‐sky outgoing longwave radiation to atmospheric temperature and water vapor

The rate at which the outgoing longwave radiation (OLR) responds to perturbations in temperature and moisture plays a fundamental role in determining climate sensitivity. This study examines the clear‐sky OLR sensitivities to temperature and water vapor, as quantified by its partial derivatives (radiative Jacobians). The Jacobians, as computed by the Geophysical Fluid Dynamics Laboratory (GFDL)'s line‐by‐line (LBL) radiative transfer model are used to verify the results from the parameterized GFDL GCM (general circulation model) radiation code. The results show that the (1) Jacobians of OLR due to incremental changes in temperature and water vapor are insensitive to different formulations of water vapor continuum absorption and (2) Jacobians of OLR are properly captured by the GCM longwave band approximation. Simulations with the GCM demonstrate that uncertainties in the formulation of continuum absorption have little impact on the climate model simulation of clear‐sky OLR changes in response to prescribed sea surface temperature (SST) perturbation. The numerically computed Jacobians of OLR are used to reconstruct the tropical annual mean OLR from the variations of temperature and water vapor over the period 1980–1999. The reconstructed OLR anomaly time series agrees well with that computed explicitly by the GCM. On the basis of this result, it becomes possible to separate out the temperature and water vapor contributions to the OLR variation. The results show that the temperature contribution dominates the water vapor contribution in the lower and middle troposphere, while in the upper troposphere the two contributions largely offset each other.

Spectroscopic and electrochemical properties of cyclopalladated complexes based on dibenzo[a,c]phenazine

Cyclopalladated complexes based on dibenzo[a,c]phenazine were studied by 1H NMR and electronic absorption and emission spectroscopy, and cyclic voltammetry. Replacement of ethylenediamine by heterocyclic ligands scarcely affects the coordination-induced proton shifts of the diazine part of the cyclometalated ligand, but, as the basicity of chelated ligands decreases, the screening of protons of the carbanionic part of those cyclometalated ligands which is the most proximate to the coordination center regularly decreases. Cyclopalladation reveals itself in the following characteristic parameters of photo-and electro-induced electron-transfer processes: longwave absorption band, λmax (437±7) nm and e (3.0±1.5) × 103 l mol−1 cm−1, vibration-structured low-temperature luminescence resulting from spin-forbidden optical transition from the excited to ground state of the complex with the energy E ∞ (16.98±0.03) kK and the lifetime τ (190±20) μs, and reversible one-electron electroreduction wave with E 1/2 −(1.39±0.03) V.

Application of synthetic-aperture radars for measuring the Faraday rotation angle

The influence of the ionosphere on polarization characteristics of the electromagnetic radiation of a spacebome synthetic-aperture radar is analyzed. The value of the Faraday rotation angle of a linearly polarized wave radiated by this radar into the ionosphere is estimated for a comparatively long-wave band. A technique is proposed for determining the Faraday rotation angle by measuring the reflectivity of the Earth’s surface with a polarimetric radar. This technique is independent of the mapped geometry and orientation of reflected elements of the Earth’s surface.

Synthesis, structure, and solvatochromism of merocyanine dyes based on barbituric acid

Di-, tetra-, and hexamethinemerocyanines were synthesized on the basis of barbituric and 1,3-dimethylbarbituric acids and heterocycles characterized by a strong (1-benzyl-1,2-dihydrobenzo[cd]indole), medium (1,3-dihydro-1,3,3-trimethyl-2H-indole and 3-ethyl-2,3-dihydro-1,3-benzothiazole), and strong electron-donor power (1,3-diphenyl-2,3-dihydro-1H-benzimidazole). Their solvatochromic properties were analyzed using both conventional parameters (absorption maxima and molar absorption coefficients) and centroids, oscillator strengths, widths, asymmetry and excess coefficients, and fine structure of the long-wave absorption bands, which were determined by mathematical processing (method of moments). A combination of these parameters unambiguously characterizes limiting electronic states of merocyanines (neutral polyene, polymethine, or charged polyene) responsible for the type of solvatochromism. Relations were found between solvatochromic properties, on the one hand, and donor-acceptor power of the terminal groups, length of the polymethine chain, and solvent nature, on the other. The difference in solvatochromism (up to reversal of sign) of merocyanines derived from barbituric acid and their analogs based on 1,3-dimethylbarbituric acid originates from both the difference in their electronic asymmetry and the ability of the NH groups in the former to participate in hydrogen bonding with proton-acceptor solvents.

A fast infrared radiative transfer model for overlapping clouds

A fast infrared radiative transfer model (FIRTM2) appropriate for application to both single-layered and overlapping cloud situations is developed for simulating the outgoing infrared spectral radiance at the top of the atmosphere (TOA). In FIRTM2 a pre-computed library of cloud reflectance and transmittance values is employed to account for one or two cloud layers, whereas the background atmospheric optical thickness due to gaseous absorption can be computed from a clear-sky radiative transfer model. FIRTM2 is applicable to three atmospheric conditions: (1) clear-sky, (2) single-layered ice or water cloud, and (3) two simultaneous cloud layers in a column (e.g., ice cloud overlying water cloud). Moreover, FIRTM2 outputs the derivatives (i.e., Jacobians) of the TOA brightness temperature with respect to cloud optical thickness and effective particle size. Sensitivity analyses have been carried out to assess the performance of FIRTM2 for two spectral regions, namely the longwave (LW) band (587.3–1179.5 cm −1) and the short-to-medium wave (SMW) band (1180.1–2228.9 cm −1). The assessment is carried out in terms of brightness temperature differences (BTD) between FIRTM2 and the well-known discrete ordinates radiative transfer model (DISORT), henceforth referred to as BTD (F−D). The BTD (F−D) values for single-layered clouds are generally less than 0.8 K. For the case of two cloud layers (specifically ice cloud over water cloud), the BTD (F−D) values are also generally less than 0.8 K except for the SMW band for the case of a very high altitude (>15 km) cloud comprised of small ice particles. Note that for clear-sky atmospheres, FIRTM2 reduces to the clear-sky radiative transfer model that is incorporated into FIRTM2, and the errors in this case are essentially those of the clear-sky radiative transfer model.

Experimental and theoretical investigation of the electronic absorption spectra of 2-H(methyl, methylthio, phenyl)-3,4-dihydro-4-quinazolinylidenecyanoacetic ester

The effect of substituents (Me, SMe, Ph) in position 2 has been studied on the nature of the absorption bands of 2-H-3,4-dihydro-4-quinazolinylidenecyanoacetic esters and a very high sensitivity on the substituent has been detected for the short wave maxima. On the basis of data calculated by the ZINDO/S method the featureless long-wave absorption band was assigned to an electronic transition from HOMO to LUMO caused by charge transfer from fragments of the benzene ring and the N=C—N bond to the >C=C—C=O fragment.

A Study of Waveband Assignment in Waveband Switching Optical Network

Tremendous internet traffic makes DWDM (Dense Wavelength Division Multiplexing) technology popularly applied in optical network and the scale of optical cross-connect (OXC) becomes larger. In order to save node cost and realize traffic grooming, waveband switching (WBS) with many new algorithms for lightpath establishment has been proposed. In this paper, the concept of RWA (routing and wavelength assignment) in wavelength-routed network is extended to RRA (routing and resource assignment) in hierarchical optical network. And a kind of resource assignment policy for RRA is proposed according to the path granularity. Then several new dynamic waveband assignment algorithms for sequential multi-granularity OXC (MG-OXC) in WBS network without wavelength converters are presented. They are SBP (shortest waveband path), FBP (first-fit waveband path), LBP (longest waveband path) and LBC (longest waveband combination) algorithms. Numerical results show that LBP algorithm is simple and more effective for middle-scale WBS optical network and LBC algorithm is suitable for large-scale one.

Features of Grana Organization in Pea Chloroplasts

Two fractions of membrane fragments—the pellets precipitated at 1300 and 20000 g (fractions G1.3 and G20, respectively)—were isolated from pea (Pisum sativum L.) chloroplasts after solubilization with digitonin. These fragments assigned to grana displayed the following differences: (1) in spectra of low-temperature fluorescence, the ratio of short-wave and long-wave band intensities, as well as integrated intensity of the whole spectrum, were higher for G1.3 than for G20 fraction; (2) in excitation spectra of long-wave fluorescence, the ratio of peaks at 650 and 680 nm and integrated intensity of the spectrum were higher for G1.3 than for G20 fraction; and (3) the shapes of fluorescence excitation spectra differed for G1.3 and G20. These results indicate that the two fractions examined differed in proportion of photosystem I and photosystem II complexes, as well as in organization of these complexes. The size of light-harvesting antenna was larger in PSI complexes of G1.3 fraction, owing, in particular, to a higher content of chlorophyll a/b-protein complexes in this fraction. After repeated digitonin fragmentation of G1.3 and G20 preparations, more than 80% of G1.3 fraction was decomposed into lighter fragments, whereas G20 fraction was resistant to fragmentation (it lost about 10% of its material). Analysis of the data suggests the presence of two structurally different types of thylakoids in grana. The yield of G20 fraction (about 20%) is comparable to the ratio between the number of intergranal thylakoids, connected to granum in pea chloroplasts, and the total number of thylakoids in this granum. Based on these data, we assume that G20 fraction represent the fragments of intergranal thylakoids that extend into the granum.

Photochromic properties of 2-(N-acetyl-N-arylaminomethylene)benzo[b]furan-, thiophene-, selenophene- and tellurophene-3(2H)-ones

Novel photochromic systems - (2Z)-2-(N-acetyl-N-arylaminomethylene)benzo(b)tellurophene- 3(2H)-ones have been synthesized. Their properties were studied in comparison with analogous benzo(b)furan, benzo(b)thiophene, and benzo(b)selenophene derivatives. The long-wave absorption band of these compounds shifts bathochromically in the following order of heteroatoms: O < S < Se < Te from 380 nm to 455 nm and the quantum yields of photoinitiated N→O acyl rearrangement (including Z/E-isomerization around the C=C bond and fast thermal migration of the acetyl group) increase from 0.60 (S) to 0.71 (Te). The acid catalyzed reverse O→N acyl rearrangement constant rates are 1.1 · 10 -4 s -1 (Te) < 4.2 10 -4 s -1 (Se) < 1.0 10 -3 s -1 (S).

Photoelectron emission caused by surface plasmons in silver nanoparticles

A new intense band of photoelectron emission peaked at a wavelength of 490 nm has been observed in granular silver films with a nanoparticle size of 10–50 nm. Coinciding with an optical reflection band, the new photoelectron emission peak is related to the excitation of surface plasmons in silver nanoparticles. The quantum yield of photoemission (0.25%) for the new band is approximately equal to that for a longwave band of the classical silver-oxygen-cesium photocathode. It is demonstrated that the photoelectron emission from both photoemitters has a common nature and a time constant on the order of several femtoseconds can be obtained.

中間波長帯を使用した赤外線法による外壁剥離診断の実験的研究

This paper studies characters of thermograph, which measured by three band wavelength infrared rays on the diagnosis for external walls. For smooth surface, long-wave band and short-wave band receive influence from the reflection. Other way, middle-wave band hardly receive the reflection, by function of the air as the filter to cut noise origin. So, middle-wave band has the advantage to diagnose smooth tile surface. And it's hopeful to improve the precision to find removed tile.

Pigment–Protein Complexes and the Number of Reaction Centers of the Photosystems in Pea Chlorophyll Mutants

We studied fluorescent and absorption properties of the chloroplasts and pigment–protein complexes isolated by gel electrophoresis from the leaves of pea, the parent cultivar Torsdag and mutants chlorotica 2004 and 2014. Specific fluorescence peaks of chlorophyll forms in individual complexes have been determined from the absorption and fluorescence spectra of the chloroplast chlorophyll and their second derivatives at 23 and –196°C. The mutant chlorotica 2004 proved to have an increased intensity of a long-wave band of the light-harvesting complex I at both 23°C (745 nm) and –196°C (728 nm). At the same time, this mutant manifested a decreased accumulation of the chlorophyll forms making up the nearest-neighbor antenna of the PS I reaction center (at 690, 697, and 708 nm). No spectral differences have been revealed between chlorotica 2014 mutant and the parent cultivar. Gel electrophoresis revealed the synthesis of all chlorophyll–protein complexes in both mutants. At the same time, analysis of photochemical activity of PS I and PS II reaction centers and calculations of their number and the size of the light-harvesting antenna have shown that the number of reaction centers in the PS I of chlorotica 2004 mutant is reduced by a factor of 1.7 because its chlorophyll a–protein complex is disturbed by the mutation. The primary effect of chlorotica 2014 mutation remains unclear. The proportional changes in the content of photosystem complexes in this mutant suggest that they are secondary and result from a 50% decrease in chlorophyll content.

The B-band luminosities of quasar host galaxies

We report on the analysis of B-band imaging data of 57 low-redshift quasi-stellar objects (quasars/QSOs) and Seyfert 1 galaxies selected from the Hamburg/ESO Survey, for which hostgalaxy-dependent selection biases are greatly reduced compared with other optical surveys. Only one object in the sample is known to be radio-loud. We adopted a procedure to remove the active galactic nuclei (AGN) contribution by subtracting a scaled point spread function from each QSO image. To reclaim the integrated host galaxy flux we correct for oversubtraction based on simulations. This method is quite insensitive to the host galaxy morphological type, which we can unambiguously establish for 15 of the 57 objects. The quasar host galaxies are detected in all cases. The hosts are very luminous, ranging in absolute magnitude MB from −19.0 to −23.8, with an average of M B,gal =− 21.5, considerably above L ∗ for field galaxies. For the luminous QSO subsample with MB < −23 the average host absolute magnitude is M B,gal =− 23.0, while for the complementary low-luminosity AGN we obtain M B,gal =− 21.2, roughly equal to L ∗ . The luminous host galaxies in the sample are typically ∼1 mag brighter than expected when inferring B-band luminosities from studies of similar objects at longer wavebands. We argue that this mismatch is not likely to be explained by selection effects, but favours host galaxy colours significantly bluer than those of inactive galaxies. Although published B-band data are scant, this result and the findings of other authors are in good agreement.