Series Of Absorption Bands Research Articles

Engineering visible light emitting point defects in Zr-implanted polycrystalline AlN films

We have investigated the impact of thermal annealing gaseous atmosphere of argon, nitrogen, and forming gas on the structural and optical properties of thin polycrystalline AlN films subjected to high-energy zirconium ions implantation. X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and atomic force microscopy measurements show that the structural and morphological properties of the Zr-implanted AlN films depend on the annealing gaseous environment. Post-implantation annealing under argon atmosphere yields the lowest structured surface roughness with increased grain size. Photoluminescence spectroscopy revealed multiple point defects and defect complexes related emission bands in the visible range. A series of absorption bands have been observed using photoluminescence excitation spectroscopy. The origin of the emission or absorption bands is identified and attributed to various types of point defects and defect complexes, theoretically reported for AlN. New emission and absorption peaks at 1.7eV (730nm) and 2.6eV (466nm), respectively, have been identified and attributed to the (ZrAl–VN)0 defect complexes.

Sulfophthalide cycle cleavage and formation of fluorenyl structures upon poly(diphenylene sulfophthalide) thermolysis

Thermolysis of poly(diphenylene sulfophthalide) (PDSP) in the temperature range from 100 to 500 °C was studied by IR and UV-Vis spectroscopy and thermogravimetric analysis. A series of absorption bands in the IR spectrum of PDSP were assigned on the basis of the theoretical calculations of the IR spectrum of diphenyl sulfophthalide used as a model compound, in particular, νas(S=O) = 1352 cm−1, νs(S=O) = 1196 cm−1, ν(C-O) ∼ 920 cm−1, ν(S-O) = 824 cm−1, and δ(SO2) = 576 cm−1. The sulfophthalide cycle (SPC) in PDSP decomposes at the thermolysis temperatures in a range of 260–400 °C. An analysis of the IR spectra of the thermolyzate and the quantum chemical calculations of the IR spectra of the model compounds confirmed the predominant formation of fluorenyl structures in the thermolyzed polymer. The changes in the UV-Vis spectra observed upon the thermolysis of thin films of PDSP (the hypsochromic shift of the long-wavelength absorption band from 271 to 263 nm and the appearance a shoulder at ∼310 nm) and the results of TD-DFT calculations of the UV-Vis spectra of the model compounds are consistent with the hypothesis about the formation of fluorenyl structures. The general scheme of PDSP thermolysis at 260–400 °C was proposed in which the major process is the formation of fluorenyl fragments in macromolecules of the polymer due to the intramolecular ring closure in biradicals formed by the SPC cleavage.

Importance of spin–orbit coupling effect and solvent effect in electronic transition assignments of PtII complexes: In the case of cis/trans-[PtIICl2(NH3)2

Electronic excitation spectra of cis-platin (cis-[PtIICl2(NH3)2]), which is a well-known antitumor drug, and trans-platin (trans-[PtIICl2(NH3)2]) were experimentally observed and theoretically analyzed using ab initio spin–orbit CASPT2 (SO-CASPT2) calculations. Cis-platin showed two series of absorption bands in the wavelength regions of 250–350nm and 350–450nm. On the other hand, trans-platin showed three series of absorption bands in the wavelength regions of 260–280nm, 300–340nm and 360–400nm. Comparing SO-CASPT2 calculations at the optimum structures in gas-phase conditions with those in DMF solvent, which were obtained by PCM implicit solvation model, it was clarified that both spin–orbit effect and solvent effect cannot be negligible even for quantitative assignments of electronic excitation spectra of cis/trans-platin.

Polarised infrared and Raman studies of YCa 4O(BO 3) 3 a non-linear optical single crystal

YCa 4O(BO 3) 3-(YCOB) is a non-linear optical (NLO) material grown by Czochralski technique. Polarised IR, ATR–IR, polarised Raman and optical transmission spectral measurements were made. A series of absorption bands have been observed with intensities depending on the functional groups of the crystals. The observed bands were assigned and discussed.

IR absorption spectroscopy of water in CsLiB6O10 crystals

AbstractPolarized absorption spectra of CsLiB 6 O 10 crystals have been measured between )186 and 25 C in the 1500–7500cm 1 wavenumber range. A series of absorption bands have been observed with intensities depending on the thermalhistory of the crystals. Three of them have been assigned as the fundamental H–O–H bending mode (d ¼ 1650 cm 1 ),and symmetric and asymmetric OH stretching modes of the bound H 2 O molecule (m s ¼ 3413 cm 1 and m a ¼ 3581 cm 1 ,respectively). Additional features in the 3800–4400, 4700–5300 and 6500–7100 cm 1 ranges have been interpreted asovertones and combinations of the fundamental H 2 O vibrations. The above assignments have been verified by detectingthe isotopic replica of the bands in a crystal treated in D 2 O vapour atmosphere. The possible sites for the H 2 O moleculein the lattice have been deduced from polarization angle dependence measurements. 2003 Elsevier B.V. All rights reserved. PACS: 42.70.Mp; 61.72.)y; 78.30.HvKeywords: FTIR spectroscopy; H

Radiation-induced shallow donors in Czochralski-grown silicon crystals saturated with hydrogen

Far-infrared absorption has been investigated in n-type Czochralski-grown silicon saturated with hydrogen and then irradiated with fast electrons. Two series of absorption bands in the range 200–330 cm−1 are observed upon postirradiation annealing of the crystals at 300–550 °C. These bands are associated with ground–to–excited-state electronic transitions in two kinds of shallow donors with ionization energies of 37.0 and 42.6 meV, which are described well with the effective-mass approximation. These donors are related to defects observed earlier in electrical measurements.

Studies of Higher Triplet Exciton Bands through T-T Absorption in Naphthalene Single Crystal

Two T - T transitions in naphthalene crystals have been identified: one with a series f vibronic progressive absorption bands between 3500 A and 4500 A is assigned as the 3 B 1 g - ← 3 B 2 u + transition, and the other with a series of absorption bands between 4500 A and 6000 A is assigned as the 3 A 1 g + ← 3 B 2 u + transition. The shape of the absorption band for the former transition has been studied between 20 K and room temperature, with the result that the shape has no temperature dependence above 80 K while the shape and the polarization change at lower temperatures. The absorption is concluded to be due to a band-to-band transition and the width of the 3 B 1 g - exciton band is determined to be 1050 cm 1 .

Study of Orientational Transformations of Supramolecular Structures on the Surfaces of Uniaxially Stretched Elastomers

Abstract Characteristics of surface orientation of cis poly(butadiene) elastomers with covalent crosslinks were studied with data from MPTIR ir spectroscopy and electron microscopy. It was shown that the supramolecular structures observed in electron photomicrographs of uniaxially stretched elastomer surfaces and their spatial reorganization correlate completely with changes in dichroism of a series of absorption bands in the MPTIR ir spectra. It was established that the maximal dichroism values in the MPTIR spectra correspond to orientation of coarse fibrillar forms, and the subsequent dichroism decline, corresponds to their deorientation. It was shown that, according to the extent of deorientation of the coarse fibrils, an increase in the cross section of the thin fibrils occurs with sharper margins separating them from the disordered part of the polymer; it was established by this that in the MPTIR spectra Rxy is partly increased, the intensity of a series of vibrations grows, and new absorption bands appear. The indicated facts are explained as due to intrafibrillar crystallization.

Chemical conversion of a tetrafluorethylene-ethylene copolymer during radiolysis in vacuum

IR spectroscopic studies of a tetrafluorethylene-ethylene (1:1) copolymer exposed to γ-radiation in vacuum revealed changes in chemical structure dependent on conditions of irradiation. With an increase in the dose of radiation a reduction occurs in absorption band intensities in the regions of 1450 and 2973 cm −1 corresponding to vibrations of CH 2 groups and in a series of absorption bands in the 500–1300 cm −1 region, corresponding to bond-stretching and deformation vibrations of CF bonds of CF 2 groups. These variations are intensified with an increase in the temperature of radiation from 25 to 250°. Different types of double bond are formed: −CH=CF−, −CF=CF−, −CH=CF 2 (bands at 1720, 1740, 1765 cm −1). Absorption band intensity varied in the region of 1740 cm −1 according to the dose and temperature of radiations. With an increased radiation dose (25°) band intensity at 1860 cm −1 related to “terminal unsaturation” of −CF=CF 2 increases. However, at an irradiation temperature of 250° this band disappears. At increased temperature of radiation (150, 250°) a broad absorption band is formed in the region of 1600–1700 cm −1, which is due to the formation of double bonds of the type −CH=CH 2 or −CH=CH−. Using results obtained a mechanism is proposed for breakdown and structure formation taking place during the irradiation of the copolymer.

Room-Temperature Ferromagnetic Materials Transparent in the Visible

The only known crystals which have a spontaneous ferromagnetic moment at room temperature and are transparent well into the visible spectrum are ferric borate, FeBO3, and ferric fluoride, FeF3. Each of these rhombohedral materials is a canted antiferromagnet with a small moment lying in the plane perpendicular to its unique axis. The Curie temperatures are 348° and 363°K and the room-temperature moments are 115 and 40 G, respectively. Both materials contain ferric ions in a slightly distorted octahedral environment. Both are green with a series of absorption bands in the visible, a fundamental absorption edge in the violet (FeBO3) or ultraviolet (FeF3), and a large Faraday rotation per unit absorption at room temperature, as high as 14°/dB at 5250 Å for FeBO3 and 16°/dB at 4050 Å for FeF3. Recent measurements of the magnetic, optical, magneto-optical, and microwave resonance properties of these materials are discussed. Potential applications of room temperature transparent ferromagnets include microwave magneto-optical modulation of visible lasers with very low modulation power per unit bandwidth, optical deflection and isolation, magneto-optic displays, and holograms. Each of these applications is discussed along with the limitations imposed by the optical absorption and birefringence of the available materials. Birefringence interferes with the Faraday effect in most noncubic crystals. Methods for minimizing this interference are described. Finally, requirements for useful transparent ferromagnets are defined and guidelines for finding new materials are suggested.

Optical properties of antimony tri-iodide

Single crystals of pure antimony tri-iodide in which the optic axis is normal to the crystal plate have been prepared. The ordinary refractive index of antimony tri-iodide has been determined at wavelengths in the absorption edge and out to a wavelength of 2.5 pm. Crystals of the com pound have been shown to be uniaxial negative and the dispersion of the birefringence has been measured. The ordinary and extraordinary refractive indices calculated from the ionic refractivity of iodine agree with the experimental values. Antimony tri-iodide has a long-wavelength absorption edge at about 5000 Å, the variation of absorption coefficient with photon energy being in agreement with Urbach’s equation. Measurements of the light transmitted through an evaporated film 0.1 pm thick at 125 °K have shown that the absorption spectrum consists of a series of absorption bands having absorption coefficients of about 105 cm -1 . These absorption bands have been attributed to two hydrogenlike series of absorption levels, the first members of each series (separation 0.46 eV) being the halogen doublet due to (3/2, 1/2) splitting. The oscillator strength of the first member of the long-wavelength series is 0.65 x 10 -4 per atom at 125 °K. Reflexion measurements from a single crystal at 173 °K have shown that two reflectivity maxima occur in positions corresponding to the absorption bands of the halogen doublet. Photoconductivity has been observed in single crystals at room temperature. The temperature and light intensity dependence of the photocurrent suggests that the photocurrent arises from the thermal dissociation of the exciton states of the halogen doublet.

Cyclization of Diene Polymers

Abstract 1. During the cyclization of natural rubber (unmasticized pale crepe) in phenol solution containing P2O5 as a catalyst, there is a drop in viscosity of the solutions—sharply at the beginning of the process and insignificantly after 5 hours cyclization time. 2. The speed of solution of rubber in phenol containing P2O5 is considerably greater than in pure phenol. This indicates that cyclization is started in the gel state and proceeds to full solution, and accelerates the breakdown of the gel fraction of the rubber. 3. Release of acetic acid, during oxidation of rubber for various periods of cyclization with chromic acid, diminishes in the course of the first four hours of the process, and then remains constant, whereas the viscosity continues to lessen. This serves to show that the process of breakdown goes forward even after the cyclization process is completed. 4. Unsaturation of cyclorubber, determined by the reaction with perbenzoic acid, amounts to approximately 25% of the original known unsaturation of rubber. 5. The presence in the ultraviolet spectrograph of cyclorubber of absorption bands at 275–280 mµ and in the infrared spectrograph of a series of absorption bands at 690 and 740−1, and again at 1500 to 1600 cm−1, indicates bound phenol in cyclorubber.

Ultraviolet Absorption Spectrum of Ammonia in Solid Argon at 4.2°K

A series of absorption bands in the region 1600 to 1900 A has been observed in thin films of solid argon containing between 0.3% and 3% of ammonia. The bands are attributed to isolated NH3, and the absence of alternating bands in the observed vibrational progression shows that in the ground state only the J = 0 level is appreciably populated. Thermal equilibration of NH3 at 4.2°K involves the interconversion of nuclear spin species. It is suggested that the observed rapid equilibration is due to coupling between the proton spins and the spin of the nitrogen nucleus.

Spectrophotometric methods for the determination of osmium-I: Extraction and ultraviolet spectrophotometric determination of osmium tetroxide

An ultraviolet spectrophotometric method is presented for the détermination of milligram quantities of osmium in solutions of uranyl sulphate. Osmium is first oxidised to the octovalent state and the osmium tetroxide which is formed, is selectively extracted with chloroform. The ultraviolet absorption spectrum'of osmium tetroxide in chloroform has a series of absorption bands with peak absorbancies at 282, 289, 297, 304 and 312 mμ and molar absorbancy indexes of 1870, 1760,1640, 1400 and 1000, respectively. For each wavelength, the optimum concentration range for the determination of osmium was evaluated. From 0.4 to 3.3 mg of osmium can be determined with a coefficient of variation of 3%. Of the elements tested only chloride and octovalent ruthenium interfere; however, both of these interferences can be eliminated.

The Transfer of Excitation Energy from p-Terphenyl to Riboflavin

In 1941, Szent-Gyorgyi (1) published an interesting paper entitled Towards a New Biochemistry. In this publication, he speculated that the transfer of energy in proteins was similar to that described for crystal phosphors, namely, that an electron released by external radiation travels a long distance in the crystal before meeting an impurity. At this point, the energy is released. Later, Szent-Gyorgyi (2) became discouraged over this concept of transfer of energy in biological systems owing to lack of experimental evidence for energy levels in proteins. In recent years, however, the concept of transfer of excitation energy between molecules has developed along two general lines: for liquid scintillation counters and for the absorption and utilization of light energy by the plant. It has been demonstrated that numerous compounds in organic solvents will selectively pick up excitation energy and transfer this energy to a second molecule (3-7). The plant physiologists have described such a transfer in diatoms, algae, and chlorphyll-containing bacteria (7-13). In view of these developments on the transfer of energy, it was decided to use these techniques for a study of the possible role of molecules of biological interest in the transfer of energy in liquid systems. The general concept is to study the fluorescence of two substances independently and in combination. In combination, if energy is transferred, the fluorescence of the first substance will decrease and the fluorescence of the second will increase. No attempt will be made to elucidate the actual mechanisms of the transfer (14, 15). Riboflavin was selected as a representative molecule on account of its widespread occurrence in plant and animal tissues and its function as a coenzyme in several important enzyme systems. Riboflavin has a series of absorption bands at 475, 445, 359, and 268 m, and shows fluorescence at 500 to 600 m,.

The interpretation of the infra-red and Raman spectra of the n -paraffins

Infra-red spectra of a series of crystalline n -paraffins containing an odd number of carbon atoms have been obtained. The spectrum of oriented crystals of n -nonadecane has also been examined. These new experimental results have been combined with the earlier data on the crystalline n -paraffins containing an even number of carbon atoms, and many series of absorption bands have been identified in the complete set of spectra. These regularities, as well as those present in the Raman spectra, have been interpreted in terms of CH 2 , CH 3 , and C—C stretching vibrations. Very regular distributions of frequencies have been found between 720 and 1030 cm -1 and between 1200 and ca. 1370 cm -1 , which are assigned to CH 2 rocking and wagging vibrations, respectively. The majority of the absorption bands between 1150 and 880 cm -1 can be attributed to C—C stretching or CH 3 rocking modes, and assignments are suggested for the principal series observed in this region.

The Infrared Absorption of Hydrogen Chloride in the Region 35 M and at 200° K

Considerable theory exists bearing upon the relationship between the maxima of the envelop of the double branched series of absorption bands in the near infrared for such diatomic gases as the hydrogen halides and the temperature at which absorption takes place. An attempt has been made to compare experiment and theory particularly that of Kemble,1 and Reiche.2 We have determined the absorption of hydrogen chloride in the region 3.5 μ at two temperatures 200°K and 291°K. The agreement of experiment with theory is good at 291°K, but at 200°K there is a slight departure.