Showing papers on "Absorption band published in 1980"

Method and apparatus for molecular spectroscopy, particularly for the determination of products of metabolism

Abstract: Method and apparatus for molecular spectroscopy, particularly for the determination of products of metabolism. The absorption of infrared radiation by a specimen (2) which contains the substance to be determined is measured. The absorption is measured simultaneously at two different wavelengths (λ 1 , λ 2 ), the first wavelength (λ 1 ) being so selected that upon changes in concentration of the substance to be determined in the specimen (2) only a negligibly small change, if any, of the radiation absorption takes place, while the second wavelength (λ 2 ) lies in the region of a substance-specific absorption band of the substance to be determined. After measurement of the radiation intensities (I 1 and I 2 ) at the two wavelengths (λ 1 , λ 2 ) the signal is standardized by formation of the quotient (I 2 /I 1 ). The method makes it possible to effect a quantitative reproducible measurement in the natural biological medium or in dialysates without pretreatment of the specimen and with only small amounts of substance. By suitable selection of the second wavelength (λ 2 ) a plurality of substances can be determined.

Infrared absorption spectra of SiO2 precipitates of various shapes in silicon: calculated and experimental

Abstract: It is shown that the infrared absorption band at 1230 cm−1, observed under certain conditions of oxygen precipitation in silicon, is the LO mode of SiO2 The LO mode, which is normally infrared inactive, becomes infrared active under the condition of polarization of small (<036 μm) platelets in an appropriate dielectric matrix (silicon) Infrared absorption spectra of SiO2 particles of various shapes, imbedded in silicon, have been calculated For platelet SiO2 precipitates, the spectrum shows an absorption band at 1215 cm−1, which is reasonably close to the observed band at 1230 cm−1 For SiO2 precipitates of other shapes the spectra do not exhibit this absorption band Instead, they exhibit a slightly weaker primary absorption band at 1095 cm−1, the TO mode, and a very weak band at 1170 cm−1, which is a mixed mode of longitudinal and transverse optical phonons

Absorption of light in the atmosphere by collision pairs of oxygen (O2)2

Abstract: Atmospheric absorption bands by collision complexes of oxygen have been measured in long path optical experiments. About 1.5×10−3 of the incoming solar energy is absorbed by the O4 bands in the near uv, visible and near infrared spectral regions. A larger fraction of this energy goes into the 2 km layer above the surface. The possible consequences of excited metastable (O2)2 molecules for atmospheric chemistry are discussed.

Preparation and Spectral Properties of Oxovanadium(IV), Nickel(II), Copper(II), and Palladium(II) Complexes of Tetraaza[14]annulenes

Abstract: The oxovanadium(IV), nickel(II), copper(II), and palladium(II) complexes of 5,14-dihydrodibenzo[b,i][1,4,8,1l]tetraazacyclotetradecine and 7,8,15,16,17,18-hexahydrodibenzo[b,j][1,4,8,1l]tetraazacyclotetradecine have been synthesized, and studied by electronic, vibrational, NMR, ESR, and ESCA spectroscopy. The absorption bands appearing in the energy region greater than 16800 cm−1 were attributed to π→π* transitions within a ligand molecule and metal to ligand charge-transfer transitions. The ligand-field bands were not assigned for the present complexes, because all the ligand-field bands were obscured by the π→π* and charge-transfer bands of high intensity. The metal complexes assume the square-planar configurations since no significant absorption band was detected in the region below 17000 cm−1. A strong band appearing at ca. 1620 cm−1 was assigned to the C=N stretching mode, and this band was shifted to lower frequency upon metal coordination. A V=O streching band was observed at ca. 950 cm−1 for the o...

Defects in crystalline SiO2:Optical absorption of the aluminum‐associated hole center

Abstract: Radiation‐induced optical absorption in crystalline SiO2 has been investigated in a number of synthetic quartz crystals. The dominant visible absorption band peaks at 2.5 eV and correlates directly with the paramagnetic resonance signal of the (Ale+)0 center. Similarities in behavior with the V− center in MgO suggest that a small polaron theory is applicable.

On band shapes of electronic transitions in the multimode weak coupling limit

Abstract: The influence of multidimensional Franck–Condon (FC) active vibrational subspace on the band shapes of electronic transitions is explored in the linear weak coupling limit. Given a constant (weak) coupling coefficient, computer calculated band shapes are seen to fall into three classes depending on the number of active vibrational modes, N. For large N, the electronic band of a polyatomic molecule will have a relatively weak zero–zero absorption compared to the ’’side‐band’’ absorption, which arises from a rapidly increasing density of states (DOS). For small N, a normal, weak FC progression is seen in which the peak absorption is in the zero–zero transition. The implications of the DOS/FC model are further discussed in relation to previous work. Calculations are presented to emphasize the effect of the multidimensional subspace on the relationship between the absorption band shape and the resonance Raman excitation profile.

Polarised luminescence in neutron- and proton-irradiated α-Al2O3

Abstract: The polarisation properties of the optical absorption and luminescence bands of a defect centre in fast neutron- and proton-irradiated alpha -Al2O3 have been studied at low temperatures The centre has an absorption band at 358 nm and a mirror image emission band at 379 nm Both bands show resolved vibronic structure with the zero-phonon line at 3684 nm and a Huang-Rhys factor of about 39 These bands are due to allowed electric-dipole transitions involving the same excited electronic level of a low-symmetry defect The plane-polarised light experiments show that the transition dipole moment of the defect is set at 40 degrees to the c axis of the crystal and the bands are assigned to a defect centre consisting of two next-nearest-neighbour oxygen ion vacancies which have trapped one or more electrons

Optical Reflectivity Spectrum of a CuFeS2 Single Crystal

Abstract: Critical reflectivity spectra have been measured at room temperature on a single crystal of CuFeS 2 between 0.025 and 6 eV. The experimental results have been used to calculate the optical constants, the dielectric constant and the absorption coefficient. There have been found an absorption band with peaks at 1.0 and 2.1 eV and an absorption edge at approximately 3.2 eV. The band can be assigned to the charge-transfer transition from the valence band to the empty 3d states of Fe, and the edge can be attributed to the commencement of the band to band transition. A schematical energy level diagram for CuFeS 2 is given from the result.

Far infrared magnetic resonance of deoxyhemoglobin and deoxymyoglobin

Abstract: We have used FIR magnetic resonance as a direct probe of the low lying electronic states of the high spin (S=2) ferrous ion in deoxyhemoglobin and deoxymyoglobin. In a variety of helium temperature experiments using different samples and different buffers, we have detected a broad absorption band at 3.5 cm−1 that is sensitive to the application of a magnetic field. This band is not observed in samples of oxy‐or carbonmonoxy‐hemoglobin. The integrated area of the absorption band agrees (via a Kramers–Kronig relation) with the measured values of the static susceptibility of deoxyhemoglobin at 1.2 °K. The large linewidth (3.5 cm−1) of the observed band is thought to reflect the large number of conformational substates associated with slightly different structures of the protein.

Comparison of experimental and theoretical excited-state spectra for rhodamine 6G

Abstract: The stimulated emission cross section (σ e ) and the excited-state absorption cross section ( \sigma* ) for this dye are resolved across the fluorescence and the lowest energy ground-state absorption bands. The absorption is weak ( \sim0.4 \times 10^{16} cm2), particularly at the longer wavelengths [Fig. 3(c)]. Lasing properties are predicted from Fig. 4(b), which shows a plot of the (σ e ) curve displaced with respect to the S 1 state as the zero-energy level of reference, on top of the long-axis polarized ground-state absorption band. Spectral assignments are proposed in terms of symmetry arguments based on this observation.

An infrared study of crystallization in sodium-disilicate glasses containing iron oxides

Abstract: The infrared absorption spectra of sodium-disilicate glasses containing various amounts of Fe2O3 ([Na2O · 2 SiO2]1−x [Fe2O3]x, where x = 0.05, 0.1 and 0.2) were investigated in the wavenumber range from 200–2000 cm−1. The addition of Fe2O3 to the sodium-disilicate glass does not seem to introduce any new absorption band as compared with the spectrum of a pure sodium-disilicate glass; nevertheless, a general shift of the existing absorption bands toward lower wavenumbers is observed. The amount of shift is, in fact, proportional to the content of Fe2O3 in the glass. This observation is consistent with the recently proposed structural model for the bonding of Fe3+ ions in the iron-sodium-silicate glass system. Annealing of 20 mol% iron oxide glasses at 550 and 580°C produced an extra sharp infrared absorption peak at about 610 cm−1 wavenumber. This new peak is believed to be related to the crystallized particles of the glass as concluded from both a scanning electron micrograph and an electron diffraction pattern.

Radiation effects in LiYF4

Abstract: Radiation-induced defects in LiYF4 have been studied using optical and ESR techniques. A pi -polarised absorption band at 3.99 eV is identified as the (F2-) centre. An optical band at 3.70 eV has polarisation properties characteristic of dipoles oriented in the direction of Y3+-Y3+ pairs. This band is a candidate for the F centre. Other optical bands with pi -polarisation at 3.02 eV and with sigma polarisation at 2.29 eV and 2.88 eV were not identified. These optical bands occur in nominally pure samples and also in samples doped with 1%Pr3+ and Er3+.

Reflection Spectrum of the Single Crystal of Wurster’s Blue Perchlorate

Abstract: The visible and near-infrared reflection spectrum of the single crystal of Wurster’s blue perchlorate was measured at various temperatures over the range of 30–300 K, by using the microspectrophotometric method. The absorption spectra were derived by Kramers-Kronig transformation of the reflection spectra. The intensity ratio of the (0-0) and (0-1) vibronic bands of the local-excitation associated with the π-π* (2B1u←2B2g) transition of TMPD+ was found to be anomalous when the spectrum was measured with the light polarized parallel to the b-axis, while not in the spectrum polarized parallel to the a-axis. The Davydov splitting between B3u and B2u components of this absorption band was found to be about 400 cm−1. In the antiferromagnetic (low temperature) phase below 190 K, the charge-transfer band appeared in the a-axis spectrum, showing its absorption maximum at 11.6×103 cm−1, and its intensity increased on lowering the temperature. At the same time, a marked temperature dependence was observed in the lo...

Line Shape of the Chromium (VI) Absorption Band in Sodium Borate and Sodium Silicate Glasses

Abstract: The effect of temperature on the line shape of the ultraviolet absorption bands of chromium (VI) in different (1-x) Na2O, xB2O3 (where x varied from 0.1 to 0.33), and in a 0.3Na2O, 0.7SiO2 glass was studied. The ultraviolet absorption of chromium (VI) in these glasses is characterised by two charge transfer bands centred around 250–270 nm and 350–370 nm, the location of the centre of absorption and relative intensities of the two bands depending on the borochromate/chromate ratio in the glass which in turn is dependent on the chemical composition of the glass. The 350–370 nm band has been found to be Gaussian at the top half of absorption, and exponential with wave-number at the low-energy tail of the band obeying Urbach's Rule. In all the glasses, the energy of absorption maximum decreased linearly with increasing temperature, and the bands became broader. The change in intensity of chromium (VI) absorption in different glasses with varying temperature has a satisfactory correlation with thermal expansio...

Apparatus for measuring vapor density, gas temperature, and saturation ratio

Abstract: An apparatus for measuring vapor density and saturation ratio of individual chemical species in multi-component, multi-phase systems includes means to permit measurement in supersaturated vapor and in the presence of liquid, solid and dispersed aerosol phases of the sampled gas component and of other chemical species. Active narrowband differential measurements of broad band radiation passed through the sampled environment and then isolated to a plurality of narrow wavelength bands whose wavelength is related to the gaseous absorption spectra of the sampled species permit the measurement of vapor density of individual chemical components. A concurrent passive radiometric measurement of gas temperature in a strong absorption band of a relatively constant gaseous component enables the conversion of component vapor density to component saturation ratio even in the presence of component or system supersaturation.

Thermal and optical measurements on vacancies in type IIa diamond

Abstract: Type IIa diamonds were irradiated below 250K with electrons of 1.50, 0.60 or 0.35 MeV. The radiation-induced thermal resistivity is shown to correlate with the concentration of neutral vacancies as determined by the strength of the GR 1 optical absorption band. The production of vacancies was found to saturate at high doses and to be as large as previously observed after irradiation at about 500K.

Structure, and infrared and ultraviolet spectra of protonated dimethylacetamide

Abstract: The X-ray crystal structure of the title compound was determined by the heavy-atom method from diffractometer data and refined to R 0.052 for 621 independent reflections. Crystals of NN′-dimethylacetamide hydrochloride (NN′-dimethylacetamidonium chloride) are monoclinic, space group P21 with Z= 2 in a unit cell of dimensions a= 7.343(7), b= 6.890(7), c= 6.765(7), A,β= 97.2(1)°. A difference-Fourier synthesis revealed the site of protonation of the amide to be the oxygen atom, confirming much indirect evidence. The i.r. spectrum for dichloromethane solution shows an absorption band at 1 670 cm–1, not present in that of the amide base, and assigned to ν(C–N). The u.v. spectrum for dichloromethane solution shows two weak absorption bands at 360 and 315 nm, whereas in aqueous solution there is only a single weak absorption band at 330 nm. Upon acidification of the aqueous solution, the u.v. spectrum of the protonated amide became identical with that obtained for dichloromethane solution.

IR-spectroscopic investigations of cycloalkanes

Abstract: A homologous series of cycloalkanes from (CH2)14 up to (CH2)96 as model systems for tight folding in CH2-chain molecules was investigated by infrared spectroscopy. In comparison with the corresponding spectra of the nalkanes we found two additional new absorption bands at 700 cm−1 and 1442 cm−1 which can be assigned to a characteristic fold vibration. The already known fold band in the wagging region at about 1344 cm−1 could also be found in all cycloalkane spectra. A numerical decomposition of the bands enables the calibration of the fold concentration. The Davydov splitting of the (CH2)-rocking and (CH2)-bending vibration in the melt crystallized form of the molecules (CH2)72 and (CH2)96 show the occurence of a orthorhombic subcell of the larger rings whereas the smaller rings and the larger ones in the solution crystallized form only crystallize in a monoclinic form.

Time-resolved measurements of photo-induced optical absorption and photocurrent in a-As2Se3

Abstract: Relaxation of photoinduced optical absorption (PA) and photocurrent (PC) following pulsed excitation is measured as a function of temperature in the range 295 K – 425 K. The decay of PA is well described by bimolecular recombination kinetics with a thermally activated rate coefficient b(T). The magnitude of b(T) yields a lower limit for the mobility of the PA excitation consistent with the hole drift mobility. In addition, first measurements of the time evolution of the PA spectrum are reported. The observed shift of the absorption band towards higher energy with increasing time is interpreted in terms of thermalization within a distribution of localized gap states.

Optical absorption by GAP states in hydrogenated amorphous silicon

Abstract: An absorption band peaking at ∼1.25 eV has been observed as a structure in the photovoltaic and photoconductivity spectra of several samples of hydrogenated amorphous silicon. This transition at ∼ 1.25 eV appears to be the inverse of the luminescence process, suggesting that these transitions occur between donors and acceptors.

Structure Determination of the 1,4-Cycloadduct Quenched after the High-pressure Reaction of Tetracyanoethylene with Styrene and Its Derivatives

Abstract: The electronic, 13C NMR, 1H NMR, and IR spectra of the 1,4-cycloadducts of TCNE with styrene, styrene-α-d1, p-chlorostyrene, p-methylstyrene, α-methylstyrene, and 1,1-diphenylethylene were taken at low temperatures at 1 bar after the high-pressure reaction; the 13C NMR spectra were of decisive importance in determining the structure; the other kinds of spectra were consistent with the established structure. They have an electronic absorption band around 320 nm, which is assigned to the π-π* transition of the triene system in the adducts. Neither cis- nor trans-stilbene, which have a lower ionization potential, provides the 1,4-cycloadduct even at high pressure.