Artykuły w czasopismach: „Absorption spectra”

1

Chen, J., i D. S. Venables. "A broadband optical cavity spectrometer for measuring weak near-ultraviolet absorption spectra of gases". Atmospheric Measurement Techniques Discussions 3, nr 5 (27.10.2010): 4571–602. http://dx.doi.org/10.5194/amtd-3-4571-2010.

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Abstract. Accurate absorption spectra of gases in the near-ultraviolet (300 to 400 nm) are essential in atmospheric observations and laboratory studies. This paper describes a novel incoherent broadband cavity-enhanced absorption spectroscopy (IBBCEAS) instrument for measuring very weak absorption spectra from 335 to 375 nm. The instrument performance was validated against the 3B1−X1A1 transition of SO2. The measured absorption varied linearly with SO2 column density and the resulting spectrum agrees well with published spectra. Using the instrument, we report new absorption cross-sections of O3, acetone, 2-butanone, and 2-pentanone in this spectral region, where literature data diverge considerably. In the absorption minimum between the Huggins and Chappuis bands, our absorption spectra fall at the lower range of reported ozone absorption cross-sections. The spectra of the ketones agree with prior spectra at moderate absorptions, but differ significantly at the limits of other instruments' sensitivity. The collision-induced absorption of the O4 dimer at 360.5 nm was also measured and found to have a maximum cross-section of ca. 4.0 × 10−46 cm5 molecule−2. We demonstrate the application of the instrument to quantifying low concentrations of the short-lived radical, BrO, in the presence of stronger absorptions from Br2 and O3.

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Chen, J., i D. S. Venables. "A broadband optical cavity spectrometer for measuring weak near-ultraviolet absorption spectra of gases". Atmospheric Measurement Techniques 4, nr 3 (1.03.2011): 425–36. http://dx.doi.org/10.5194/amt-4-425-2011.

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Abstract. Accurate absorption spectra of gases in the near–ultraviolet (300 to 400 nm) are essential in atmospheric observations and laboratory studies. This paper describes a novel incoherent broadband cavity-enhanced absorption spectroscopy (IBBCEAS) instrument for measuring very weak absorption spectra from 335 to 375 nm. The instrument performance was validated against the 3B1-X1A1 transition of SO2. The measured absorption varied linearly with SO2 column density and the resulting spectrum agrees well with published spectra. Using the instrument, we report new absorption cross-sections of O3, acetone, 2-butanone, and 2-pentanone in this spectral region, where literature data diverge considerably. In the absorption minimum between the Huggins and Chappuis bands, our absorption spectra fall at the lower range of reported ozone absorption cross-sections. The spectra of the ketones agree with prior spectra at moderate absorptions, but differ significantly at the limits of other instruments' sensitivity. The collision-induced absorption of the O4 dimer at 360.5 nm was also measured and found to have a maximum cross-section of ca. 4.0×10−46 cm5 molecule−2. We demonstrate the application of the instrument to quantifying low concentrations of the short-lived radical, BrO, in the presence of stronger absorptions from Br2 and O3.

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Hewitt, Paul. "Absorption Spectra". Physics Teacher 43, nr 2 (luty 2005): 74. http://dx.doi.org/10.1119/1.1855739.

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Jensen, Peter Snoer, Jimmy Bak i Stefan Andersson-Engels. "Influence of Temperature on Water and Aqueous Glucose Absorption Spectra in the Near- and Mid-Infrared Regions at Physiologically Relevant Temperatures". Applied Spectroscopy 57, nr 1 (styczeń 2003): 28–36. http://dx.doi.org/10.1366/000370203321165179.

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Near- and mid-infrared absorption spectra of pure water and aqueous 1.0 g/dL glucose solutions in the wavenumber range 8000–950 cm−1 were measured in the temperature range 30–42 °C in steps of 2 °C. Measurements were carried out with an FT-IR spectrometer and a variable pathlength transmission cell controlled within 0.02 °C. Pathlengths of 50 μm and 0.4 mm were used in the mid- and near-infrared spectral region, respectively. Difference spectra were used to determine the effect of temperature on the water spectra quantitatively. These spectra were obtained by subtracting the 37 °C water spectrum from the spectra measured at other temperatures. The difference spectra reveal that the effect of temperature is highest in the vicinity of the strong absorption bands, with a number of isosbestic points with no temperature dependence and relatively flat plateaus in between. On the basis of these spectra, prospects for and limitations on data analysis for infrared diagnostic methods are discussed. As an example, the absorptive properties of glucose were studied in the same temperature range in order to determine the effect of temperature on the spectral shape of glucose. The change in water absorption associated with the addition of glucose has also been studied. An estimate of these effects is given and is related to the expected level of infrared signals from glucose in humans.

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Platonov, Alexej N., Klaus Langer, Andrzej Wieviöra i Michael Andrut. "Electronic absorption spectra of chromium-bearing amesite". European Journal of Mineralogy 7, nr 4 (1.08.1995): 961–66. http://dx.doi.org/10.1127/ejm/7/4/0961.

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Closca, V., C. B. Zelinschi, D. Babusca i D. O. Dorohoi. "Solvent Empirical Scales for Electronic Absorption Spectra". Ukrainian Journal of Physics 59, nr 3 (marzec 2014): 226–32. http://dx.doi.org/10.15407/ujpe59.03.0226.

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Dotsenko, M. A. "ABSORPTION AND LUMINESCENCE PROPERTIES OF ACID AND SALT FORMS OF MONONUCLEOTIDES, THEIR COMPONENTS AND COMPLEXES WITH D-MANNITOL AT ROOM TEMPERATURE". Biotechnologia Acta 17, nr 2 (30.04.2024): 36–37. http://dx.doi.org/10.15407/biotech17.02.036.

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Aim. The aim of this work was to analyze and compare spectral properties of aqueous nucleotide solutions in conditions close to biological systems. We studied the absorption and luminescence (Ex and Em fluorescence and Em phosphorescence) of monoribonucleotides, their disodium salts, bases and nucleosides, and mixes with D-mannitol dissolved in water at room temperature. Methods. There were measured absorbance spectra using a Specord 210plus instrument and fluorescence excitation and emission and phosphorescence spectra using Horiba Fluoro Max 4+ instruments. Results. There were obtained the absorption, excitation, and luminescence spectra of aqueous solutions 1 mg/ml of nucleotides, their components, and mixtures with mannitol (in ratio 1:4). We observed a change in the ratio between the peaks of the spectra of acidic and salt forms of nucleotides. Conclusions. The observations confirmed that nucleotides, nucleosides, and nucleic acid bases exhibit luminescence at room temperature, which might be useful information for further research in this area. In addition, a comparative analysis of the spectra showed possible interactions between nucleotide molecules and mannitol.

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Wagner, T., S. Beirle, T. Deutschmann, M. Grzegorski i U. Platt. "Satellite monitoring of different vegetation types by differential optical absorption spectroscopy (DOAS) in the red spectral range". Atmospheric Chemistry and Physics 7, nr 1 (10.01.2007): 69–79. http://dx.doi.org/10.5194/acp-7-69-2007.

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Abstract. A new method for the satellite remote sensing of different types of vegetation and ocean colour is presented. In contrast to existing algorithms relying on the strong change of the reflectivity in the red and near infrared spectral region, our method analyses weak narrow-band (few nm) reflectance structures (i.e. "fingerprint" structures) of vegetation in the red spectral range. It is based on differential optical absorption spectroscopy (DOAS), which is usually applied for the analysis of atmospheric trace gas absorptions. Since the spectra of atmospheric absorption and vegetation reflectance are simultaneously included in the analysis, the effects of atmospheric absorptions are automatically corrected (in contrast to other algorithms). The inclusion of the vegetation spectra also significantly improves the results of the trace gas retrieval. The global maps of the results illustrate the seasonal cycles of different vegetation types. In addition to the vegetation distribution on land, they also show patterns of biological activity in the oceans. Our results indicate that improved sets of vegetation spectra might lead to more accurate and more specific identification of vegetation type in the future.

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Wagner, T., S. Beirle, M. Grzegorski i U. Platt. "Satellite monitoring of different vegetation types by differential optical absorption spectroscopy (DOAS) in the red spectral range". Atmospheric Chemistry and Physics Discussions 6, nr 4 (16.08.2006): 7945–58. http://dx.doi.org/10.5194/acpd-6-7945-2006.

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Abstract. A new method for the satellite remote sensing of different types of vegetation and ocean colour is presented. In contrast to existing algorithms, our method analyses weak narrow-band reflectance structures (i.e. "fingerprint" structures) of vegetation in the red spectral range. It is based on differential optical absorption spectroscopy (DOAS), which is usually applied for the analysis of atmospheric trace gas absorptions. Since the spectra of atmospheric absorption and vegetation reflectance are simultaneously included in the analysis, the effects of atmospheric scattering and absorption are automatically corrected. The inclusion of the vegetation spectra also significantly improves the results of the trace gas retrieval. The global maps of the fitting coefficients for the vegetation spectra (indicating the fraction of the observed ground scene covered by vegetation) illustrate the seasonal cycle of different vegetation types. In addition to the vegetation distribution on land, they also show patterns of biological activity in the oceans. Our results indicate that improved sets of vegetation spectra might lead to more accurate and more specific identification of vegetation type in the future.

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Imanian, A., M. H. Tangestani i A. Asadi. "INVESTIGATION OF SPECTRAL CHARACTERISTICS OF CARBONATE ROCKS – A CASE STUDY ON POSHT MOLEH MOUNT IN IRAN". ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLII-4/W18 (18.10.2019): 553–57. http://dx.doi.org/10.5194/isprs-archives-xlii-4-w18-553-2019.

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Abstract. Recent developments in the image processing approaches and the availability of multi and/or hyper spectral remote sensing data with high spectral, spatial and temporal resolutions have made remote sensing technique of great interest in investigations of geological sciences. One of the biggest advantage of the application of remote sensing in geology is recognizing the type of unknown rocks and minerals. In this study, an investigation on spectral features of carbonate rocks (i.e. calcite, dolomite, and dolomitized calcite) were done in terms of main absorptions, the reasons of those absorptions and comparison of these absorption with Johns Hopkins University (JHU) spectral library and laboratory spectra of Analytical Spectral Devices (ASD) instrument. For this purpose, we used the VNIR and SWIR bands of ASTER and OLI datasets. Finally, we applied the Spectral Analyst Algorithm in order to comparison between the obtained spectra from ASTER dataset and carbonate spectra of JHU spectral library.

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INOUE, SHUN-ICHI, NAOTO KOSHIZAKI i TETSUYA KODAIRA. "FORMATION OF Te NANOWIRES IN ZEOLITE AFI AND THEIR POLARIZED ABSORPTION SPECTRA". International Journal of Modern Physics B 19, nr 15n17 (10.07.2005): 2817–22. http://dx.doi.org/10.1142/s0217979205031754.

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Te atoms were loaded into nanochannels of zeolite AFI single crystals. The polarized absorption and Raman scattering spectra were measured. The absorption spectra of Te loaded AFI showed large anisotropic properties. The absorption spectra of E//c deeply depended on the loading density of Te atoms. In low Te loading density, Te was adsorbed into the nanochannels in a dimer form whose absorption peak appeared at ca. 3.5 eV . In high loading density, Te form one dimensional nanowires inside the channels. Nanowire formation causes large anisotropic absorption and changes in the spectral shape.

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Kotlikov, E. N., N. P. Lavrovskaya, I. K. Miloushev i T. K. Tenev. "Investigation of optical constants of Al₂O₃ films in the spectral range 0.2 - 0.8 microns". Journal of Physics: Conference Series 2436, nr 1 (1.01.2023): 012005. http://dx.doi.org/10.1088/1742-6596/2436/1/012005.

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Abstract We determine optical constants of Al2O3 films deposited by electron beam evaporation on a quartz substrate in the spectrum range 0.2-0.8 microns. Refractive index and extinction coefficient are determined by a spectrophotometric method using the reflection and transmission spectra. An original method of correction of the spectra of the films is used taking into account the absorption. The refractive index is determined from absorption-free spectra, and the extinction coefficient is determined from absorption spectra in the specified spectral region.

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Kolosov, N. A., S. S. Boldova i V. A. Labusov. "Investigation of atomic vapor absorption spectra on the high-resolution spectrometer "Grand-2000"". Interexpo GEO-Siberia 8, nr 1 (18.05.2022): 112–16. http://dx.doi.org/10.33764/2618-981x-2022-8-1-112-116.

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The work is devoted to the study of atomic vapor absorption spectra obtained in the electrothermal atomizer (graphite furnace) and registered by the high-resolution spectrometer "Grand-2000" (spectral resolution 4 pm). Comparison of the obtained spectra with the spectra recorded by the "Grand-2" spectrometer, which is a part of the "Grand-AAS" atomic absorption spectrometer, indicated the presence of unresolved spectral interferences in the latter, as well as a number of unresolved doublets of analytical lines, both already presented in the database of spectral absorption lines of chemical elements, and missing in it. Based on the results of the work, we can talk about the suitability of the "Grand-2000" spectrometer for adjusting this database.

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Kaplan, H. H., A. A. Simon, V. E. Hamilton, M. S. Thompson, S. A. Sandford, M. A. Barucci, E. A. Cloutis i in. "Composition of organics on asteroid (101955) Bennu". Astronomy & Astrophysics 653 (wrzesień 2021): L1. http://dx.doi.org/10.1051/0004-6361/202141167.

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Context. The Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRIS-REx) mission detected an infrared absorption at 3.4 μm on near-Earth asteroid (101955) Bennu. This absorption is indicative of carbon species, including organics, on the surface. Aims. We aim to describe the composition of the organic matter on Bennu by investigating the spectral features in detail. Methods. We use a curated set of spectra acquired by the OSIRIS-REx Visible and InfraRed Spectrometer that have features near 3.4 μm (3.2 to 3.6 μm) attributed to organics. We assess the shapes and strengths of these absorptions in the context of laboratory spectra of extraterrestrial organics and analogs. Results. We find spectral evidence of aromatic and aliphatic CH bonds. The absorptions are broadly consistent in shape and depth with those associated with insoluble organic matter in meteorites. Given the thermal and space weathering environments on Bennu, it is likely that the organics have not been exposed for long enough to substantially decrease the H/C and destroy all aliphatic molecules.

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Allen, G., J. J. Remedios, D. A. Newnham, K. M. Smith i P. S. Monks. "High resolution mid-infrared cross-sections for peroxyacetyl nitrate (PAN) vapour". Atmospheric Chemistry and Physics Discussions 4, nr 5 (22.09.2004): 5655–81. http://dx.doi.org/10.5194/acpd-4-5655-2004.

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Abstract. Absorption spectra of peroxyacetyl nitrate (PAN, CH3C(O)OONO2) vapour at room temperature (295 K) have been measured in the mid-infrared range, 550–2200 cm−1 (18.2–3.33 µm), using a Fourier transform infrared spectrometer at instrument resolutions of 0.25 and 0.03 cm−1 (unapodised). Both cross-section data and integrated absorption intensities for the five principal bands in the PAN spectra in this spectral range have been derived from fourteen separate PAN transmission spectra measurements. Band intensities and band centre absorptivities are also reported for four weaker PAN absorption bands in the mid infrared for the first time. These observations are the highest spectral resolution measurements of PAN bands recorded in the infrared to date. For three of the five strongest bands, the absolute integrated absorption intensities are in excellent agreement with previous studies. A 4.8% lower integrated intensity was found for the 1741 cm−1 νas (NO2) PAN absorption band, possibly as a result of the removal in this work of spectra affected by subtle acetone contamination, while a 10.6% higher intensity was determined for the 1163 cm−1 ν (C-O) absorption band. No direct effects of spectral resolution were observed. The improved accuracy of these absorption cross-sections will allow more accurate investigations of PAN using infrared spectroscopy, particularly for remote sensing of PAN in the atmosphere.

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Wallace, S., S. G. Lambrakos i L. Massa. "Density function theory (DFT) calculated infrared absorption spectra for nitrosamines". Water Science and Technology 80, nr 10 (15.11.2019): 1967–74. http://dx.doi.org/10.2166/wst.2020.018.

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Abstract Absorption spectra within the infrared (IR) range of frequencies for nitrosamines in water are calculated using density function theory (DFT). Calculated in this study, are the IR spectra of C2H6N2O, C4H10N2O, C6H14N2O, C4H8N2O, C3H8N2O, and C8H18N2O. DFT calculated absorption spectra corresponding to vibration excited states of these molecules in continuous water background can be correlated with additional information obtained from laboratory measurements. The DFT software Gaussian was used for the calculations of excited states presented here. This case study provides proof of concept, viz., that such DFT calculated spectra can be used for their practical detection in environmental samples. Thus, DFT calculated spectra may be used to construct templates, for spectral-feature comparison, and thus detection of spectral-signature features associated with target materials.

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Chyży, K. T., W. Jurusik, J. Piotrowska, B. Nikiel-Wroczyński, V. Heesen, V. Vacca, N. Nowak i in. "LOFAR MSSS: Flattening low-frequency radio continuum spectra of nearby galaxies". Astronomy & Astrophysics 619 (listopad 2018): A36. http://dx.doi.org/10.1051/0004-6361/201833133.

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Aims. The shape of low-frequency radio continuum spectra of normal galaxies is not well understood, the key question being the role of physical processes such as thermal absorption in shaping them. In this work we take advantage of the LOFAR Multifrequency Snapshot Sky Survey (MSSS) to investigate such spectra for a large sample of nearby star-forming galaxies. Methods. Using the measured 150 MHz flux densities from the LOFAR MSSS survey and literature flux densities at various frequencies we have obtained integrated radio spectra for 106 galaxies characterised by different morphology and star formation rate. The spectra are explained through the use of a three-dimensional model of galaxy radio emission, and radiation transfer dependent on the galaxy viewing angle and absorption processes. Results. Our galaxies’ spectra are generally flatter at lower compared to higher frequencies: the median spectral index αlow measured between ≈50 MHz and 1.5 GHz is −0.57 ± 0.01 while the high-frequency one αhigh, calculated between 1.3 GHz and 5 GHz, is −0.77 ± 0.03. As there is no tendency for the highly inclined galaxies to have more flattened low-frequency spectra, we argue that the observed flattening is not due to thermal absorption, contradicting the suggestion of Israel & Mahoney (1990, ApJ, 352, 30). According to our modelled radio maps for M 51-like galaxies, the free-free absorption effects can be seen only below 30 MHz and in the global spectra just below 20 MHz, while in the spectra of starburst galaxies, like M 82, the flattening due to absorption is instead visible up to higher frequencies of about 150 MHz. Starbursts are however scarce in the local Universe, in accordance with the weak spectral curvature seen in the galaxies of our sample. Locally, within galactic disks, the absorption effects are distinctly visible in M 51-like galaxies as spectral flattening around 100–200 MHz in the face-on objects, and as turnovers in the edge-on ones, while in M 82-like galaxies there are strong turnovers at frequencies above 700 MHz, regardless of viewing angle. Conclusions. Our modelling of galaxy spectra suggests that the weak spectral flattening observed in the nearby galaxies studied here results principally from synchrotron spectral curvature due to cosmic ray energy losses and propagation effects. We predict much stronger effects of thermal absorption in more distant galaxies with high star formation rates. Some influence exerted by the Milky Way’s foreground on the spectra of all external galaxies is also expected at very low frequencies.

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Беликов, А. В., А. М. Загорулько, С. Н. Смирнов, А. Н. Сергеев, А. А. Михайлова i А. А. Шимко. "Оптические свойства in vitro катарактальных хрусталиков глаза человека в видимом и ближнем ИК диапазонах-=SUP=-*-=/SUP=-". Журнал технической физики 126, nr 5 (2019): 656. http://dx.doi.org/10.21883/os.2019.05.47667.16-19.

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Spectral dependences of absorption coefficient, scattering coefficient, anisotropy factor and reduced scattering coefficient for in vitro human eye lenses of different cataract type are investigated. The spectra of absorption coefficient and reduced scattering coefficient were obtained for the spectral range 400-2300 nm, and the spectra of scattering coefficient and scattering anisotropy factor - for the spectral range 400-1800 nm. The regions of wavelengths within which the spectra of the studied optical characteristics of the human eye lens are not statistically significantly different for samples with different stages of cataract maturity and, conversely, within which they are statistically significantly different, are determined.

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Bracher, A., M. Vountas, T. Dinter, J. P. Burrows, R. Röttgers i I. Peeken. "Quantitative observation of cyanobacteria and diatoms from space using PhytoDOAS on SCIAMACHY data". Biogeosciences Discussions 5, nr 6 (28.11.2008): 4559–90. http://dx.doi.org/10.5194/bgd-5-4559-2008.

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Abstract. In this study the technique Differential Optical Absorption Spectroscopy (DOAS) has been adapted for the retrieval of the absorption and biomass of two major phytoplankton groups (PhytoDOAS) from data of the satellite sensor Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY). SCIAMACHY measures back scattered solar radiation in the UV-Vis-NIR spectral region with a high spectral resolution (0.2 to 1.5 nm). In order to identify phytoplankton absorption characteristics in SCIAMACHY data in the range of 430 to 500 nm, phytoplankton absorption spectra measured in-situ during two different RV "Polarstern" expeditions were used. The two spectra have been measured in different ocean regions where different phytoplankton groups (cyanobacteria and diatoms) dominated the phytoplankton composition. Results show clearly different absorption characteristics of the phytoplankton groups in the SCIAMACHY spectra. Globally distributed pigment concentrations for these characteristic phytoplankton groups for two monthly periods (February–March 2004 and October–November 2005) were derived from these differential absorptions by including the information of the sensor's optical paths within the water column (i.e. light penetration depth) according to Vountas et al. (2007) derived from DOAS fits of inelastic scattering. The satellite retrieved information on cyanobacteria and diatoms distribution matches well the concentrations measured at collocated water samples with HPLC technique and concentrations derived from the global model analysis with the NOBM model (Gregg et al., 2003; Gregg and Casey, 2007). Identifying quantitative distribution of key phytoplankton groups from space allow to distinguish various biogeochemical provinces and will be of great importance for the global modelling of marine ecosystem and biogeochemical cycles addressing climate changes in the oceanic biosphere.

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Винниченко, М. Я., И. С. Махов, Н. Ю. Харин, С. В. Граф, В. Ю. Паневин, И. В. Седова, С. В. Сорокин i Д. А. Фирсов. "Фотопроводимость и поглощение инфракрасного излучения в квантовых ямах p-GaAs/AlGaAs". Физика и техника полупроводников 55, nr 8 (2021): 629. http://dx.doi.org/10.21883/ftp.2021.08.51127.03.

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The spectra of low-temperature impurity-assisted far and mid-infrared photoconductivity and absorption in nanostructure with multiple GaAs/AlGaAs quantum wells doped with acceptors are investigated. The experimentally obtained absorption and photoconductivity spectra correlate well with each other. According to the hole and acceptor state energy spectrum calculations the spectral features related to the optical hole transitions from the ground acceptor state to the delocalized states of valence subbands, to the excited acceptor states and to the delocalized states above the quantum well (photoionization) are identified in the absorption and photoconductivity spectra.

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Беликов, А. В., Ю. В. Семяшкина, С. Н. Смирнов i А. Д. Тавалинская. "Исследование изменений в спектре поглощения современных хлоринсодержащих препаратов для фотодинамической терапии и метиленового синего в результате воздействия светодиодного излучения с длиной волны 656± 10 nm". Журнал технической физики 129, nr 7 (2020): 972. http://dx.doi.org/10.21883/os.2020.07.49570.55-20.

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The changes in absorption spectra of aqueous solutions of modern chlorine-containing photosensitizing preparations "Revixan" (Areal, Russia) and "Chloderm" (Chloderm, Russia) depending on the intensity of LED radiation with wavelength of 656 ± 10 nm and exposure time were studied in spectral range 600-700 nm. The parameters of the CIE Lab color model of the image of "Revixan" aqueous solution before and after LED exposure were investigated. The changes in absorption spectra of aqueous solutions of methylene blue with different initial concentrations arising after exposure to LED radiation with intensity of 180 ± 20 mW/cm2 were studied in the spectral range 400-900 nm. It was shown that the impact of LED radiation changes the absorption spectra of the studied preparations and increases the parameter L (lightness) of the CIE Lab color model for "Revixan". An increase in the LED radiation intensity and exposure time leads to a decrease in absorption for "Revixan" and "Chloderm" in spectral range 600-700 nm and to a shift of the peaks of absorption bands lying in this range towards a longer wavelength. The impact of LED radiation on aqueous solutions of methylene blue leads to a decrease in their absorption in spectral range 400-900 nm.

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Hofstraat, J. W., i M. J. Latuhihin. "Correction of Fluorescence Spectra". Applied Spectroscopy 48, nr 4 (kwiecień 1994): 436–47. http://dx.doi.org/10.1366/000370294775269027.

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Several methods that can be applied to remove wavelength-dependent instrumental effects from fluorescence emission and excitation spectra have been investigated. Removal of such artifacts is necessary for the comparison of spectra that have been obtained on different instruments. Without correction, spectral line positions and relative intensities will be instrument-determined to a great extent. Furthermore, the application of adequate correction procedures provides excitation spectra which can be directly compared to absorption spectra; comparison of corrected excitation spectra and absorption spectra can be used to interpret the efficiency and pathways of radiative processes. Finally, corrected reflection spectra can be obtained, which can be directly transformed into absorption spectra and are useful for remote sensing applications. The methods that have been studied for the correction of emission spectra are the application of a standard lamp with calibrated spectral output and the use of fluorescence standards. The standards are a series of luminescent phosphors in polymer films and a solution of quinine sulfate dihydrate in perchloric acid, all provided with certified spectral emission values. For correction of excitation spectra, a quantum counter was applied. Several quantum counters were investigated. The best results were obtained for application of a mixture of the dyes basic blue and HITC, which provided good correction for the wavelength range 250 to 820 nm. No good quantum counters have been reported thus far for this (large) wavelength range. Correction for wavelength dependence of the excitation optics was realized by measurement of the excitation light intensity at the sample position and at the reference position with a Si photodiode. Correction factors for the excitation spectra were checked with a number of reference materials. Attention has also been paid to polarization-dependent effects that may occur in fluorescence spectra. The application of correction procedures was demonstrated for phytoplankton fluorescence spectra.

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Rowan, Lawrence C., Alexander F. H. Goetz i Elsa Abbott. "Analysis of Shuttle Multispectral Infrared Radiometer measurements of the western Saudi Arabian shield". GEOPHYSICS 52, nr 7 (lipiec 1987): 907–23. http://dx.doi.org/10.1190/1.1442361.

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During the November 12–14, 1981, mission of the space shuttle Columbia, the Shuttle Multispectral Infrared Radiometer (SMIRR) recorded radiances in ten channels along a 100 m wide groundtrack across the western Saudi Arabian shield. The ten channels are located in the 0.5 to 2.4 μm region, with five positioned between 2.0 and 2.40 μm for measuring absorption features that are diagnostic of OH‐bearing and [Formula: see text] minerals. This exceptionally well exposed area consists of late Proterozoic metamorphic, intermediate to silicic intrusive, and interlayered clastic sedimentary and intermediate silicic volcanic rocks that have not been studied previously using SMIRR data. Plots or traces of unnormalized SMIRR channel ratios were examined before field studies to locate areas with high spectral contrast, especially in the 2.0 μm to 2.40 μm channels. Reflectance spectra were measured in the laboratory for rock and soil samples collected in these areas, and the mineralogic causes of the main absorption features were determined using X‐ray diffraction. Laboratory SMIRR spectra were produced by convolving the ten SMIRR filters with the laboratory spectra. Then, normalized SMIRR reflectance spectra were generated along the groundtrack using normalization coefficients calculated for a field sample representing a uniform, low‐spectral contrast area. Field evaluation shows that unnormalized SMIRR ratio traces are useful, even without specific mineralogic information, for distinguishing rocks that are characterized by Al‐OH, Mg‐OH, and/or [Formula: see text], [Formula: see text], and [Formula: see text] absorption features. Analysis of field samples permits suites of minerals causing absorption features to be identified. However, specific mineral identification cannot be achieved consistently using the SMIRR ratio traces or normalized SMIRR spectra, because the Al‐OH and Mg‐OH absorption features can be caused by more than one of the minerals commonly present. The normalized SMIRR spectra are especially useful for identifying subtle Al‐OH and Mg‐OH absorption features that are difficult to identify in the unnormalized ratio traces and for comparing the relative intensities of absorption features. Al‐OH absorption is related to muscovite, smectite, illite, and kaolinite, whereas Mg‐OH absorption is caused by chlorite, amphibole, and biotite. The principal sources of error in using SMIRR spectral measurements for identifying mineral groups along the orbit 27 groundtrack are inaccuracies in field location and lithologic heterogeneity that is not represented adequately by field samples. Calibration errors may account for systematic albedo and absorption intensity differences between calculated laboratory SMIRR spectra and normalized SMIRR spectra. SMIRR instrument noise and atmospheric factors appear to be less important sources of error. However, as higher spectral and spatial resolution systems are developed for mineral identification, radiometric precision and atmospheric factors will become more important.

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Hua, Dao‐hong, Zeng‐fu Song, Shu‐kun Wang i Zu‐xiu Rong. "Study on YAG:Nd3+ spectra. I. Absorption spectra". Journal of Chemical Physics 89, nr 9 (listopad 1988): 5398–403. http://dx.doi.org/10.1063/1.455590.

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Ridder, T., T. Warneke i J. Notholt. "Source brightness fluctuation correction of solar absorption Fourier Transform mid infrared spectra". Atmospheric Measurement Techniques Discussions 4, nr 1 (20.01.2011): 443–59. http://dx.doi.org/10.5194/amtd-4-443-2011.

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Abstract. Solar absorption Fourier Transform infrared spectrometry is considered a precise and accurate method for the observation of trace gases in the atmosphere. The precision and accuracy of such measurements are dependent on the stability of the light source. Fluctuations in the source brightness reduce the precision and accuracy of the trace gas concentrations, but cannot always be avoided. Thus, a strong effort is made within the community to reduce the impact of source brightness fluctuations by applying a correction on the spectra following the measurements. So far, it could be shown that the precision and accuracy of CO2 total column concentrations could be improved by applying a source brightness fluctuation correction to spectra in the near infrared spectral region. The analysis of trace gas concentrations obtained from spectra in the mid infrared spectral region is fundamental. However, spectra below 2000 cm−1 are generally considered uncorrectable, if they are measured with a MCT detector. Such measurements introduce an unknown offset to MCT interferograms, which prevents a source brightness fluctuation correction. Here, we show a method of source brightness fluctuation correction, which can be applied on spectra in the whole infrared spectral region including spectra measured with a MCT detector. We present a solution to remove the unknown offset in MCT interferograms allowing MCT spectra for an application of source brightness fluctuation correction. This gives an improvement in the quality of MCT spectra and we demonstrate an improvement in the retrieval of O3 profiles and total column concentrations. For a comparison with previous studies, we apply our source brightness fluctuation correction method on spectra in the near infrared spectral region and show an improvement in the retrieval of CO2 total column concentrations.

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26

Khan, Zahid H. "Electronic Spectra of Radical Cations and Their Correlation with Photoelectron Spectra." Zeitschrift für Naturforschung A 42, nr 1 (1.01.1987): 91–96. http://dx.doi.org/10.1515/zna-1987-0116.

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Absorption measurements on the radical cations of 3.4,8.9-dibenzotetraphene, pentaphene, 3.4-benzopentaphene, 6.7-benzopentaphene, and naphtho-(2'.3':6.7)pentaphene are made in the spectral region 7 - 5 0 kK. Electronic spectra of the cations are calculated using the Longuet- Higgins-Pople and Wasilewski type Open-Shell SCF-MO methods with limited configuration interaction. A detailed discussion of the absorption bands is given in the light of the calculations and the electronic transition energies of the cations derived from the ultraviolet photoelectron spectra of the parent hydrocarbons. The correlation between the optical and photoelectron spectra is closely examined and it is found to be excellent.

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PRASAD, M., M. CHANDRASEKHAR i V. CHANDRA MOULI. "OPTICAL ABSORPTION AND ESR SPECTRAL STUDIES ON COPPER-DOPED LEAD-CADMIUM GLASSES". Modern Physics Letters B 19, nr 03 (10.02.2005): 119–28. http://dx.doi.org/10.1142/s021798490500813x.

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The electron spin resonance and optical absorption spectra of PbO-CdO glasses containing 1 mole% CuO have been investigated at room temperature. The optical absorption spectra of all glass samples have exhibited a broad asymmetric absorption band, which corresponds to a d–d transition of Cu 2+ ions. The prepared glass samples have been analyzed as a function of the photon energy. The results are interpreted based on the optical absorption spectral profiles and also the edge values upon the application of Davis and Mott's theory. From the ESR spectral features, the spin Hamiltonian parameters have been evaluated. The bonding coefficients were obtained, in order to elucidate the information on the Cu 2+ ligand bond nature.

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Kume, Atsushi, Tomoko Akitsu i Kenlo Nishida Nasahara. "Why is chlorophyll b only used in light-harvesting systems?" Journal of Plant Research 131, nr 6 (10.07.2018): 961–72. http://dx.doi.org/10.1007/s10265-018-1052-7.

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Abstract Chlorophylls (Chl) are important pigments in plants that are used to absorb photons and release electrons. There are several types of Chls but terrestrial plants only possess two of these: Chls a and b. The two pigments form light-harvesting Chl a/b-binding protein complexes (LHC), which absorb most of the light. The peak wavelengths of the absorption spectra of Chls a and b differ by c. 20 nm, and the ratio between them (the a/b ratio) is an important determinant of the light absorption efficiency of photosynthesis (i.e., the antenna size). Here, we investigated why Chl b is used in LHCs rather than other light-absorbing pigments that can be used for photosynthesis by considering the solar radiation spectrum under field conditions. We found that direct and diffuse solar radiation (PARdir and PARdiff, respectively) have different spectral distributions, showing maximum spectral photon flux densities (SPFD) at c. 680 and 460 nm, respectively, during the daytime. The spectral absorbance spectra of Chls a and b functioned complementary to each other, and the absorbance peaks of Chl b were nested within those of Chl a. The absorption peak in the short wavelength region of Chl b in the proteinaceous environment occurred at c. 460 nm, making it suitable for absorbing the PARdiff, but not suitable for avoiding the high spectral irradiance (SIR) waveband of PARdir. In contrast, Chl a effectively avoided the high SPFD and/or high SIR waveband. The absorption spectra of photosynthetic complexes were negatively correlated with SPFD spectra, but LHCs with low a/b ratios were more positively correlated with SIR spectra. These findings indicate that the spectra of the photosynthetic pigments and constructed photosystems and antenna proteins significantly align with the terrestrial solar spectra to allow the safe and efficient use of solar radiation.

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29

Binnemans, K., i C. Görller-Walrand. "Polarized absorption spectra of". Journal of Physics: Condensed Matter 8, nr 9 (26.02.1996): 1267–79. http://dx.doi.org/10.1088/0953-8984/8/9/017.

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Sevilla, J. M., M. Dominguez, F. Garcia-Blanco i M. Blazquez. "Resolution of absorption spectra". Computers & Chemistry 13, nr 3 (styczeń 1989): 197–200. http://dx.doi.org/10.1016/0097-8485(89)85007-7.

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Levshakov, S. A. "Absorption spectra of quasars". Astrophysics 29, nr 2 (1989): 657–71. http://dx.doi.org/10.1007/bf01005972.

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Peiris, Kamaranga H. S., Michael O. Pumphrey i Floyd E. Dowell. "NIR Absorbance Characteristics of Deoxynivalenol and of Sound and Fusarium-Damaged Wheat Kernels". Journal of Near Infrared Spectroscopy 17, nr 4 (1.01.2009): 213–21. http://dx.doi.org/10.1255/jnirs.846.

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The near infrared (NIR) absorption spectra of deoxynivalenol (DON) and single wheat kernels with or without DON were examined. The NIR absorption spectra of 0.5–2000 ppm of DON in acetonitrile were recorded in the 350–2500 nm range. Second derivative processing of the NIR spectra and spectral subtractions showed DON absorption bands at 1408 nm, 1904 nm and 1919 nm. NIR spectra of sound and Fusarium-damaged kernels were also acquired using two instruments. Subtraction of average absorption spectra and second derivative spectra were evaluated to identify different NIR signatures of the two types of kernel. Differences in peak height and positions of the NIR absorption bands of the kernels were noted. At 1204 nm, 1365 nm and 1700 nm, the differences were in the heights of the absorption peaks. Such differences may be attributed to changes in the levels of grain food reserves such as starches, proteins and lipids and other structural compounds. Shifts in absorption peak positions between the two types of kernels were observed at 1425–1440 nm and 1915–1930 nm. These differences may arise from other NIR active compounds, such as DON, which are not common for the two types of kernel. Since the NIR absorption of DON may have contributed to the shifts between sound and Fusarium-damaged kernels, this study indicates the potential for NIR spectrometry to evaluate Fusarium damage in single kernels based on the DON levels.

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33

Егорова, Н. И., И. О. Конюшенко, В. М. Немец i С. А. Пеганов. "О возможностях многомерной эквидистантной абсорбционной спектроскопии в широком диапазоне частот в исследованиях фракций термической разгонки нефти". Журнал технической физики 128, nr 4 (2020): 564. http://dx.doi.org/10.21883/os.2020.04.49208.309-19.

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The features and possibilities of absorption molecular spectroscopy of complex mixtures of organic compounds by the instance of oil thermal distillation fractions are studied. The problem of studying the spectra of oil fractions as a single object of complex molecular composition was directly solved (i.e. without studing of molecular composition). Thereby multidimensional equidistant spectra were studied in a wide spectral range. Measurement conditions: frequency range from 500 to 1500 cm-1, spectral resolution 1 cm-1, frequency increment 0.5 cm-1, Objects under investigation - 33 fractions of thermal oil distillation. Results processing of spectroscopic measurements was carried out using methods of multifactor mathematical statistics. The efficiency of using absorption molecular spectroscopy in the far infrared region in the study and control of the optical characteristics (absorption spectra) of oil thermal distillation fractions is shown.

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Yang, Juan, Daqi Zhang i Yan Li. "How to remove the influence of trace water from the absorption spectra of SWNTs dispersed in ionic liquids". Beilstein Journal of Nanotechnology 2 (30.09.2011): 653–58. http://dx.doi.org/10.3762/bjnano.2.69.

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Single-walled carbon nanotubes (SWNTs) can be efficiently dispersed in the imidazolium-based ionic liquids (ILs), at relatively high concentration, with their intrinsic structure and properties retained. Due to the hygroscopicity of the ILs, water bands may be introduced in the absorption spectra of IL-dispersed SWNTs and cause problems in spectral deconvolution and further analysis. In order to remove this influence, a quantitative characterization of the trace water in [BMIM]+[PF6]− and [BMIM]+[BF4]− was carried out by means of UV–vis-NIR absorption spectroscopy. A simple yet effective method involving spectral subtraction of the water bands was utilized, and almost no difference was found between the spectra of the dry IL-dispersed SWNT samples treated under vacuum for 10 hours and the spectra of the untreated samples with subtraction of the pure water spectrum. This result makes it more convenient to characterize SWNTs with absorption spectra in the IL-dispersion system, even in the presence of trace amount of water.

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35

Simon, A. A., H. H. Kaplan, E. Cloutis, V. E. Hamilton, C. Lantz, D. C. Reuter, D. Trang, S. Fornasier, B. E. Clark i D. S. Lauretta. "Weak spectral features on (101995) Bennu from the OSIRIS-REx Visible and InfraRed Spectrometer". Astronomy & Astrophysics 644 (grudzień 2020): A148. http://dx.doi.org/10.1051/0004-6361/202039688.

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Context. The NASA Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRIS-REx) mission has obtained thousands of spectra of asteroid (101955) Bennu with the OSIRIS-REx Visible and InfraRed Spectrometer. Aims. We present a spectral search for minor absorption bands and determine compositional variations on the surface of Bennu. Methods. Reflectance spectra with low and high spatial resolutions were analyzed for evidence of weak absorption bands. Spectra were also divided by a global average spectrum to isolate unique spectral features, and variations in the strongest band depths were mapped on a surface shape model. The global visible to near-IR spectrum of Bennu shows evidence of several weak absorption bands with depths of a few percent. Results. Several observed bands are consistent with phyllosilicates, and their distribution correlates with the stronger 2.74-μm hydration band. A 0.55-μm band is consistent with iron oxides and is deepest in the spectrally reddest areas on Bennu. The presence of hydrated phyllosilicates and iron oxides indicates substantial aqueous alteration in Bennu’s past. Conclusions. Bennu’s spectra are not identical to a limited set of carbonaceous chondrite spectra, possibly due to compositional properties and spatial scale differences; however, returned samples should contain a mixture of common chondrite materials.

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Qajar, Ch O., S. B. Kazymova, M. R. Menzeleyev i A. S. Gasanova. "Low Resolution Rotational Spectra of Phenol". Applied Physics Research 10, nr 6 (30.11.2018): 77. http://dx.doi.org/10.5539/apr.v10n6p77.

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The modeling of low-resolution (LR) microwave spectra of phenol C6H5OH molecule has been provided in the frequency regions of 0-700 GHz basing on high-resolution (HR) microwave spectral data. The frequency ranges of most intensive absorption level of low-resolution microwave spectra determined. The most intensive spectral lines forming spectra extremums are developed. The recommendations related to perspectives of practical use of achieved results are given.

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37

Jones, Cory, i Keigo Fukumura. "Probing X-Ray Continua with Accretion-Disk Wind in Black Hole X-Ray Binaries". Research Notes of the AAS 6, nr 6 (7.06.2022): 118. http://dx.doi.org/10.3847/2515-5172/ac75ed.

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Abstract High energy coronal radiation in Black Hole X-Ray Binary sources is often absorbed by accretion disk winds and the resulting absorption signatures heavily depend on its ionizing spectral energy distribution (SED). Considering multiple ion absorbers in the wind (e.g. Fe xxv/xxvi, S xvi, Si xiv, Ca xx and Mg xii), we find that the relative strength of absorption among these ions in general sensitively depends on the shape of the SED. We calculate a series of absorption line spectra from radiative transfer process for 9 distinct SED. Furthermore, we simulate 50 ks XRISM/Resolve spectra for each SED. We then fit the spectra by two-parameter wind model (SED and wind density normalization) to examine whether or not absorption features imprinted by the wind can be uniquely mapped to the ionizing SED.

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38

Ingemey, R. A., G. Strohe i W. S. Veeman. "Dynamic Infrared Linear Dichroic Spectra of Prestretched Polypropylene". Applied Spectroscopy 50, nr 11 (listopad 1996): 1360–65. http://dx.doi.org/10.1366/0003702963904746.

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DIRLD (dynamic infrared linear dichroic) spectra of prestretched isotactic polypropylene have been recorded. The line shape features in the in-phase spectra are described on the basis of frequency shifts and absorption amplitude variations during the stretching cycle. Details such as the dichroism of the bands, direction of the shift, and changes in the absorption intensities must be considered to explain signs and shapes of the DIRLD bands. Evidence for chain reorientations under stress has not been found. The general principle of frequency shifts and changes in absorption intensities as the origin of DIRLD bands is demonstrated by spectral simulations.

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39

Tanimoto, Hiroki, Xu Hongkun, Masaishiro Mizumaki, Yoshiki Seno, Jumpei Uchiwada, Ryo Yamagami, Hiroyuki Kumazoe i in. "Non-negative matrix factorization for 2D-XAS images of lithium ion batteries". Journal of Physics Communications 5, nr 11 (1.11.2021): 115005. http://dx.doi.org/10.1088/2399-6528/ac3268.

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Abstract Lithium-ion secondary batteries have been used in a wide variety of purposes, such as for powering mobile devices and electric vehicles, but their performance should be improved. One of the factors that limits their performance is the non-uniformity of the chemical reaction in the process of charging and discharging. Many attempts have been made to elucidate the mechanism behind this reaction non-uniformity. In this paper, to detect non-uniformity in various physical properties from Co K-edge two-dimensional x-ray absorption spectroscopy (2D-XAS) images of lithium ion batteries, we propose a method that consists of one-sided orthogonal non-negative matrix factorization in combination with removal of the reference signal. The difference between x-ray absorption spectra acquired at different positions in the battery is very small. However, even in such a situation, our method can decompose the 2D-XAS data into different spatial domains and their corresponding absorption spectra. From the spectral decomposition of the obtained absorption spectra, we confirmed a transition-energy shift of the main peak as evidence for a change in the state of charge and also found spectral changes due to orbital hybridization in the decomposed spectral components.

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40

Yappert, M. Cecilia, i J. D. Ingle. "Absorption-Corrected Spectral Studies of the Lucigenin Chemiluminescence Reaction". Applied Spectroscopy 43, nr 5 (lipiec 1989): 767–71. http://dx.doi.org/10.1366/0003702894202111.

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With a spectrometer based on two multichannel detectors, luminescence and absorption spectra are acquired simultaneously during the reaction between lucigenin and H2O2 in a basic solution. Alterations in the fluorescence and chemiluminescence spectral contours occur during the reaction, due to time-dependent inner filter effects caused by the changing absorption of the emission radiation by reactants, intermediates, or products. The spectrometer uses the measured absorbances and appropriate equations for automatic correction of luminescence spectra for inner filter effects. The corrected spectra demonstrate that the primary fluorescent product of the reaction, N-methyl acridone, is not the primary chemiluminescent emitting species.

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41

Chin, Sanghoon, Jérôme Van Zaen, Séverine Denis, Enric Muntané, Stephan Schröder, Hans Martin, Laurent Balet i Steve Lecomte. "An Artificial Neural Network to Eliminate the Detrimental Spectral Shift on Mid-Infrared Gas Spectroscopy". Sensors 23, nr 19 (3.10.2023): 8232. http://dx.doi.org/10.3390/s23198232.

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We demonstrate the successful implementation of an artificial neural network (ANN) to eliminate detrimental spectral shifts imposed in the measurement of laser absorption spectrometers (LASs). Since LASs rely on the analysis of the spectral characteristics of biological and chemical molecules, their accuracy and precision is especially prone to the presence of unwanted spectral shift in the measured molecular absorption spectrum over the reference spectrum. In this paper, an ANN was applied to a scanning grating-based mid-infrared trace gas sensing system, which suffers from temperature-induced spectral shifts. Using the HITRAN database, we generated synthetic gas absorbance spectra with random spectral shifts for training and validation. The ANN was trained with these synthetic spectra to identify the occurrence of spectral shifts. Our experimental verification unambiguously proves that such an ANN can be an excellent tool to accurately retrieve the gas concentration from imprecise or distorted spectra of gas absorption. Due to the global shift of the measured gas absorption spectrum, the accuracy of the retrieved gas concentration using a typical least-mean-squares fitting algorithm was considerably degraded by 40.3%. However, when the gas concentration of the same measurement dataset was predicted by the proposed multilayer perceptron network, the sensing accuracy significantly improved by reducing the error to less than ±1% while preserving the sensing sensitivity.

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42

Báscones, A., M. Suárez, M. Ferrer-Julià, E. García-Meléndez, E. Colmenero-Hidalgo i A. Quirós. "Caracterización de minerales de arcilla y óxidos de hierro mediante espectroscopía de reflectancia difusa (VNIR–SWIR)". Revista de Teledetección, nr 55 (23.06.2020): 49. http://dx.doi.org/10.4995/raet.2020.13331.

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<p>The mineralogical analysis was carried out through the spectral properties developed by samples of soils and sediments from the northwestern edge of the Duero Basin. The absorptions produced by the oxides and Feoxyhydroxides (mainly hematite and goethite) are located in VNIR zones (400-1200 nm), while the absorption bands that are present in the SWIR spectra (1200-2500 nm) are related to the chemical composition of clay minerals. The reflectance spectra measured in the laboratory have been normalized by using the methods of Continuum Removal (CR) and the second derivative (SD). This last method can solve the band overlapping because it quantifies subtle drops in the curve. This has allowed the absorption bands to be examined separately by measurement of their geometrical parameters. The proportion of the minerals affects the spectral response and, accordingly, the values of the parameters. Linear correlations were conducted between these values and the proportion of the different mineral phases obtained by X-ray diffraction. In the studied parameters, the correlation between the band center (BC) position in the maximum absorption around the wavelengths at 890-960 nm and the absorption feature depth at 470 nm (D470) has enabled a relative estimation of the proportion of hematite/goethite. As for the distribution of the different clay minerals, a correlation has been established between the proportion of kaolinite and the absorption bands depth at 1415 and 2210 nm, and in the absorption features near 1390 and 2160 nm, analyzed in SD.<em></em></p>

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Okoshi, Katsuya, Yosuke Minowa, Nobunari Kashikawa, Toru Misawa, Daichi Kashino, Hajime Sugai, Kazuya Matsubayashi, Atsushi Shimono i Shinobu Ozaki. "Multiple Mg ii Absorption Systems in the Lines of Sight to Quadruply Lensed Quasar H1413+1143". Astronomical Journal 162, nr 5 (4.10.2021): 175. http://dx.doi.org/10.3847/1538-3881/ac0bbb.

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Abstract We find multiple Mg ii absorption systems at redshift z = 1.66, 2.069, and 2.097 in the spatially resolved spectra of the quadruply gravitationally lensed quasar H1413+1143 utilizing the Kyoto tridimensional spectrograph ii (Kyoto 3D ii) spectrograph on board the Subaru telescope. Here we present the first measurement of differences in Mg ii absorption strength of the multiple intervening absorbers, which include ones identified as damped Lyα (DLA) absorption systems. Our detection of the significant Mg ii absorptions in the spatially resolved spectra reveals the inhomogeneous chemical enrichment on scales of about 12 kpc within the separation of the four sight lines. For the DLA system at z = 1.66, the rest equivalent widths (EWs) of the Mg ii absorption lines between the four spatially resolved lines of sight change by factors of up to ∼6, which trace the variations in the H i absorption strength. This suggests that inhomogeneous cold absorbers that give rise to the strong H i/Mg ii absorptions dwell on a scale of about 6–12 kpc between the four lines of sight. We also investigate the degree of variation in the EW of the absorption lines between the lines of sight. We find that the systems giving rise to strong absorptions in the spectra of the quadruply lensed quasars tend to have a high degree of variation in absorption strength between the lines of sight toward the lensed quasars.

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44

Кривобок, В. С., Д. А. Литвинов, С. Н. Николаев, Е. Е. Онищенко, Д. А. Пашкеев, М. А. Чернопицский i Л. Н. Григорьева. "Экситонные эффекты и примесно-дефектное излучение в GaAs/AlGaAs-структурах, применяемых для изготовления детекторов среднего ИК-диапазона". Физика и техника полупроводников 53, nr 12 (2019): 1632. http://dx.doi.org/10.21883/ftp.2019.12.48617.9214.

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AbstractA series of undoped GaAs/Al_ x Ga_1 –_ x As multiple quantum well heterostructures, whose doped analogs are used for the production of photodetectors operating in the spectral range 8–12 μm, is fabricated by molecular-beam epitaxy. For the heterostructures, the spectral position of absorption lines corresponding to the allowed transitions between quantum-confined electron and hole levels in GaAs layers is established. The influence of impurity–defect states on the luminescence and absorption spectra of quantum wells is studied. The excitonic corrections for the allowed transitions are determined in relation to the quantum-well width and the aluminum content in the barrier layers. The role of excitonic effects in restoring the structure of single-electron states from interband-absorption spectra (luminescence-excitation spectra) and the relationship between these states and the working region of IR photodetectors based on GaAs/Al_ x Ga_1 –_ x As quantum wells are discussed.

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45

Sorour, Mohammed I., Andrew H. Marcus i Spiridoula Matsika. "Modeling the Electronic Absorption Spectra of the Indocarbocyanine Cy3". Molecules 27, nr 13 (24.06.2022): 4062. http://dx.doi.org/10.3390/molecules27134062.

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Accurate modeling of optical spectra requires careful treatment of the molecular structures and vibronic, environmental, and thermal contributions. The accuracy of the computational methods used to simulate absorption spectra is limited by their ability to account for all the factors that affect the spectral shapes and energetics. The ensemble-based approaches are widely used to model the absorption spectra of molecules in the condensed-phase, and their performance is system dependent. The Franck–Condon approach is suitable for simulating high resolution spectra of rigid systems, and its accuracy is limited mainly by the harmonic approximation. In this work, the absorption spectrum of the widely used cyanine Cy3 is simulated using the ensemble approach via classical and quantum sampling, as well as, the Franck–Condon approach. The factors limiting the ensemble approaches, including the sampling and force field effects, are tested, while the vertical and adiabatic harmonic approximations of the Franck–Condon approach are also systematically examined. Our results show that all the vertical methods, including the ensemble approach, are not suitable to model the absorption spectrum of Cy3, and recommend the adiabatic methods as suitable approaches for the modeling of spectra with strong vibronic contributions. We find that the thermal effects, the low frequency modes, and the simultaneous vibrational excitations have prominent contributions to the Cy3 spectrum. The inclusion of the solvent stabilizes the energetics significantly, while its negligible effect on the spectral shapes aligns well with the experimental observations.

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Savoie, Carole, i Christian Reber. "Near-infrared and visible luminescence and absorption spectroscopy of low-coordinate organometallic rhenium compounds". Canadian Journal of Chemistry 74, nr 1 (1.01.1996): 28–31. http://dx.doi.org/10.1139/v96-003.

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Low-temperature absorption and luminescence spectra of four organorhenium compounds were measured in the visible and near-infrared spectral regions. Effects of the temperature, formal oxidation state, and the oxo-, bromo-, and organic ligands on the metal center are reported. The emission maxima of the four compounds show a large variation between 9000 and 14 200 cm−1. Stokes shifts show a smaller variation from 3700 to 4200 cm−1. Luminescence intensities are used to qualitatively characterize nonradiative relaxation processes. Key words: luminescence spectra, absorption spectra, organorhenium compounds.

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47

Arrivo, S. M., V. D. Kleiman, W. T. Grubbs, T. P. Dougherty i E. J. Heilweil. "Infrared Spectral Hole Burning of 1:1 Hydrogen-Bonded Complexes in Solution". Laser Chemistry 19, nr 1-4 (1.01.1999): 1–10. http://dx.doi.org/10.1155/1999/80323.

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Transient picosecond infrared (IR) spectra of the OH and NH-stretch (v=0–1) absorption bands of several hydrogen-bonded complexes have been investigated. Solutions of 1:1 complexes of weak acids (methanol, triethylsilanol and pyrrole, < 0.1 mol/dm3) and bases (acetonitrile, pyridine and tetrahydrofuran, < 2 mol/dm3) in CCl4 at 295 K were interrogated with IR excitation and broadband probing. Lorentzian-shaped absorption bands are uniformly bleached while those with near-Gaussian bandshapes produce transient spectral holes. These results indicate a base functionality and hydrogen-bond strength dependence for determining the broadening mechanisms of these absorptions.

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El-Kader, M. S. A., G. Maroulis i T. Bancewicz. "Spectral lineshapes of collision-induced absorption (CIA) using isotropic intermolecular potential for N2-CH4". Journal of Computational Methods in Sciences and Engineering 21, nr 4 (28.09.2021): 1063–78. http://dx.doi.org/10.3233/jcm-210049.

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Quantum mechanical lineshapes of collision-induced absorption (CIA) at different temperatures are computed for gaseous mixtures of molecular nitrogen and methane using theoretical values for the induced dipole moments and intermolecular potential as input. Comparison with theoretical absorption spectra shows satisfactory agreement. An empirical model of the dipole moment which reproduces the experimental spectra and the first three spectral moments more closely than the fundamental theory, is also presented. Good agreement between computed and experimental absorption lineshapes is obtained when a potential model which is constructed from the thermophysical and transport properties is used.

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Brackmann, Christian, Marcus Aldén, Per-Erik Bengtsson, Kent O. Davidsson i Jan B. C. Pettersson. "Optical and Mass Spectrometric Study of the Pyrolysis Gas of Wood Particles". Applied Spectroscopy 57, nr 2 (luty 2003): 216–22. http://dx.doi.org/10.1366/000370203321535141.

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A detailed experimental investigation has been made of the pyrolysis—the first step in biomass combustion—of single birchwood particles. In addition to mass spectrometric and gravimetric analysis, the pyrolysis volatiles were characterized by different optical techniques. Absorption measurements showed a nearly featureless absorption in the ultraviolet spectral region with a continuously stronger absorption for shorter wavelengths. Using different excitation wavelengths, laser-induced fluorescence measurements revealed generally broad spectra in the spectral region from 300–500 nm, which are characteristic spectral signatures for larger hydrocarbons. The optical data were monitored at different times in the pyrolysis process of the particles and compared with the results from the mass spectrometric and gravimetric analysis. The sensitivity of the optical techniques for differentiation between specific molecules was rather low, although formaldehyde could be observed both in absorption and fluorescence spectra. Laser-induced fluorescence measurements were also made for two-dimensional visualization of the pyrolysis volatiles emitted from heated birchwood particles, indicating much higher flows along the fiber direction than across.

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Hazen, Kevin H., Mark A. Arnold i Gary W. Small. "Temperature-Insensitive Near-Infrared Spectroscopic Measurement of Glucose in Aqueous Solutions". Applied Spectroscopy 48, nr 4 (kwiecień 1994): 477–83. http://dx.doi.org/10.1366/000370294775268910.

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A digital Fourier filter is combined with partial least-squares (PLS) regression to generate a calibration model for glucose that is insensitive to sample temperature. This model is initially created by using spectra collected over the 5000 to 4000 cm−1 spectral range with samples maintained at 37°C. The analytical utility of the model is evaluated by judging the ability to determine glucose concentrations from a set of prediction spectra. Absorption spectra in this prediction set are obtained by ratioing single-beam spectra collected from solutions at temperatures ranging from 32 to 41°C to reference spectra collected at 37°C. The temperature sensitivity of the underlying water absorption bands creates large baseline variations in prediction spectra that are effectively eliminated by the Fourier filtering step. The best model provides a mean standard error of prediction across temperatures of 0.14 mM (2.52 mg/dL). The benefits of the Fourier filtering step are established, and critical experimental parameters, such as number of PLS factors, mean and standard deviation for the Gaussian shaped Fourier filter, and spectral range, are considered.

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