scholarly journals STUDY OF STRUCTURAL AND SPECTRAL CHARACTERISTICS OF CRYSTAL Y3Al5O12, Al2O3 AND SrTiO3 DOPED BY 3d- OR 4f- IONS

2016 ◽  
Vol 7 (2) ◽  
Author(s):  
Slavica Maletić ◽  
Dušan Popović ◽  
Dragana Cerović ◽  
Jablan Dojčilović
Keyword(s):  
Dielectric Permittivity ◽  
Absorption Spectra ◽  
Dielectric Spectroscopy ◽  
Structural Phase ◽  
Spectral Characteristics ◽  
Aluminum Ions ◽  
Laser Crystals ◽  
Wide Energy ◽  
The Subject ◽  
Structural And Spectral Characteristics

The subject of our research is a study of the effects of various treatments on the structural and spectral characteristics of oxides (Y3Al5O12, Al2O3 and SrTiO3) belonging to the group of ionic crystals with a wide energy band gap. We have investigated the dielectric and optical characteristics of single laser crystals of Y3Al5O12 (YAG) doped by ions from the group of iron (3d-), Al2O3 single crystal and SrTiO3 crystals doped by 3d and 4f- ions. Dielectric properties of the investigated single crystals were analyzed using dielectric spectroscopy (80 kHz – 15 MHz) in a wide temperature range (50 – 400 K). The comparison of the temperature dependence of the dielectric permittivity (εr) and dielectric loss (tanδ) at different test frequencies for undoped and doped crystals was performed. The optical properties were studied on the basis of the absorption spectra in the UV-Vis region. The experiment results showed that presence of 3d dopants in YAG crystal caused a displacement of the absorption edge and appearance of characteristic peaks. The differences observed in the absorption spectra were probably the result of the 3d ions incorporation on two possible symmetrically different positionings of aluminum ions –tetrahedrical and octahedrical– in the YAG crystal lattice. The dielectric spectroscopy measurements for samples of SrTiO3 doped by 4f ions showed anomalous behaviors of the dielectric permittivity at temperatures around the temperature of the structural phase transition 105 K.

Structural and spectral characteristics of water molecules in aquacomplexes of uranyl nitrates

1996 ◽  
Vol 63 (5) ◽  
pp. 621-624
Author(s):  
A. P. Zazhogin ◽  
A. A. Zazhogin ◽  
A. I. Komyak ◽  
A. I. Serafimovich
Keyword(s):  
Spectral Characteristics ◽  
Water Molecules ◽  
Structural And Spectral Characteristics

scholarly journals The Origin of Absorption Spectra in Quasi-Stellar Objects

1980 ◽  
Vol 92 ◽  
pp. 107-117 ◽  
Author(s):  
Ray J. Weymann
Keyword(s):  
Absorption Line ◽  
Absorption Spectra ◽  
Classification Scheme ◽  
Spectral Characteristics ◽  
Type A ◽  
Galactic Halos ◽  
Evolutionary Sequence ◽  
Rich Cluster ◽  
Stellar Objects ◽  
Quasi Stellar Objects

A classification scheme for QSO absorption line spectra is described which ascribes the origin of the lines to at least four mechanisms: (A) Explosive ejection of material at speeds up to 0.1 c. (B) Absorption by highly ionized material moving in a rich cluster in which the QSO is embedded. (C-1) Cosmologically distant intervening material with ‘normal’ abundances, probably associated with large galactic halos. (C-2) Cosmologically distant intervening material consisting of primordial uncondensed gas. Examples of each type of spectra are given and their ionization and other spectral characteristics discussed. The similarity between the development of novae spectra and a possible evolutionary sequence of the explosive ejecta of type A is striking and suggestive. Several difficulties and unsolved problems involving this scheme are noted. Finally, we speculate on the interpretation of two interesting objects (PKS 0237-23 and the ‘twin quasars’ 0957+56A,B) in the context of this scheme.

UV and IR Spectral Characteristics of Chloramben in Selected Environments

Weed Science ◽  
1976 ◽  
Vol 24 (1) ◽  
pp. 107-114 ◽  
Author(s):  
V. E. Berkheiser ◽  
J. L. Ahlrichs
Keyword(s):  
Ir Spectra ◽  
Water Content ◽  
Absorption Spectra ◽  
Spectral Characteristics ◽  
Uv Absorption ◽  
Hydration Water ◽  
Carboxyl Group ◽  
Amino Group ◽  
Acid Base ◽  
Uv Absorption Spectra

Ultraviolet (UV) absorption spectra were recorded of chloramben (3-amino-2,5-dichlorobenzoic acid) and selected relatives in solutions of different pH's. From these spectra, the Broensted acid-base properties of chloramben were deduced. Interpretations of solution spectra were applied to UV absorption spectra of chloramben adsorbed onto Ca-montmorillonite at low water content. Infrared (IR) transmittance spectra were recorded of chloramben and selected derivatives in KBr pellets and band assignments were made. Interpretations of these spectra were also applied to IR spectra of chloramben adsorbed onto Ca-montmorillonite at low water content. Both UV and IR measurements indicated that protonation of the amino group occurs and that the carboxyl group of chloramben is strongly hydrogen-bonded to the hydration water of the interlayer cations.

scholarly journals Morphological, structural, and spectral characteristics of amorphous iron sulfates

2015 ◽  
Vol 120 (4) ◽  
pp. 809-830 ◽  
Author(s):  
E. C. Sklute ◽  
H. B. Jensen ◽  
A. D. Rogers ◽  
R. J. Reeder
Keyword(s):  
Spectral Characteristics ◽  
Amorphous Iron ◽  
Structural And Spectral Characteristics

Neutron-diffraction study of the structural phase transitions in the antifluorite K2PtBr6

1985 ◽  
Vol 63 (7) ◽  
pp. 988-996 ◽  
Author(s):  
Robin L. Armstrong ◽  
Rose M. Morra ◽  
Brian M. Powell
Keyword(s):  
Phase Transitions ◽  
Nuclear Quadrupole Resonance ◽  
Goodness Of Fit ◽  
Structural Phase ◽  
Spectral Characteristics ◽  
Neutron Diffraction Study ◽  
Structural Phase Transitions ◽  
Quadrupole Resonance ◽  
Nuclear Quadrupole

Neutron-powder-diffraction profiles are reported for the antifluorite K2PtBr6 at temperatures of 296, 160, 141, and 120 K. Bromine nuclear-quadrupole-resonance measurements have shown that each of these temperatures corresponds to a different crystal structure and have provided information on the most probable structures. A variety of structural models with symmetries obtained from a group theoretical classification of structural phase transitions are fitted to the diffraction data. A comparison of goodness-of-fit parameters for the models considered at each temperature allows the space group of each phase to be identified. The results provide (i) a definitive test of the validity of a classification scheme proposed for nuclear-quadrupole-resonance spectral characteristics, and (ii) support for the proposition that the allowable, continuous distortions of a crystal are given by the nondisruptive criterion rather than the more restrictive group–subgroup criterion.

Absorption spectra of high purity metallic and semiconducting single-walled carbon nanotube thin films in a wide energy region

2011 ◽  
Vol 151 (22) ◽  
pp. 1696-1699 ◽  
Author(s):  
Masao Ichida ◽  
Shingo Saito ◽  
Tadashi Nakano ◽  
Ye Feng ◽  
Yasumitsu Miyata ◽  
...  
Keyword(s):  
Thin Films ◽  
Carbon Nanotube ◽  
Absorption Spectra ◽  
High Purity ◽  
Energy Region ◽  
Single Walled Carbon Nanotube ◽  
Single Walled Carbon ◽  
Wide Energy

scholarly journals Absorption spectra of burning hydrocarbons

1933 ◽  
Vol 142 (846) ◽  
pp. 26-39 ◽  
Keyword(s):  
Absorption Spectra ◽  
Ultra Violet ◽  
Ultra Violet Light ◽  
Violet Light ◽  
Combustible Gas ◽  
End Products ◽  
Different Temperatures ◽  
The Subject

There is much yet to learn about the manner in which various hydrocarbons burn. The methods employed to gain information on the subject up to the present have been chiefly chemical, for instance, the estimation of the amount if products formed at different temperatures. It was hoped that a different method might divulge new facts. The idea was to pass a beam of ultra-violet light along a tube through which a mixture of combustible gas was passed at such temperatures that combustion was just commencing, and to observe by a spectrograph the changes in the absorption of the light. Although for the combustion of hydrocarbons there is an essential difficulty, because the products of initial stages of the reaction are likely to be masked by the accumulation of the end products, yet certain interesting facts have been discovered, which it is the purpose of tins communication to record. The experiments are of a preliminary character designed to test in what directions the method can yield useful information about combustion.

scholarly journals SPECTROPHOTOMETRIC STUDY OF ACID-BASE PROPERTIES OF SPATIAL-DISTORTED DERIVATIVES OF PORPHYRINS IN ACETONITRILE

2018 ◽  
Vol 59 (6) ◽  
pp. 49 ◽  
Author(s):  
Yulia B. Ivanova ◽  
Svetlana G. Puhovskaya ◽  
Nugzar Zh. Mamardashvili ◽  
Oscar I. Koifman
Keyword(s):  
Absorption Spectra ◽  
Molecular Form ◽  
Spectral Characteristics ◽  
Reaction System ◽  
Spectrophotometric Titration ◽  
Spectrophotometric Study ◽  
Acidic Properties ◽  
Acid Base ◽  
Electron Absorption ◽  
Base Properties

Spectrophotometric titration method was used to study the acidic properties of: 5,10,15,20-tetrakis(thienyl-2-yl)-2,3,7,8,12,13,17,18-octaethylporphyrin (I), 5,10,15,20-tetrakis(4’-t-butylphenyl)-2,3,7,8,12,13,17,18-octaethylporphyrin (II), 5,10,15,20-tetrakis(3,5-di-t-butylphe-nyl)-2,3,7,8,12,13,17,18-octaethylporphyrin (III), 5,10,15,20-tetraphenyl-2,3,7,8,12,13,17,18-octaethylporphyrin (IV), 5,15-bis(4’-methoxyphenyl)-10,20-bis(4-nitro-phenyl)-2,8,12,18-tetrame-thyl-3,7,13,17-tetraarylporphyrin (V), 5,15-bis(4’-methoxyphenyl)-10,20-diphenyl-2,3,7,8,12,13, 17,18-octaethylporphyrin (VI), 5,15-bis(4’-methoxyphenyl)-2,8,12,18-tetramethyl-3,7,10,13,17,20-hexaethylporphin (VII), 5,10,15,20-tetrakis(4’-methoxyphenyl)-2,3,7,8,12,13,17,18-octaethylpor-phyrin (VIII) in the presence of a deprotonated agent, 1,8-diazabicyclo[5.4.0] undec-7-ene, in acetonitrile. Under deprotonation two families of spectral curves in the absorption spectra, having its own system of isobestic points, are formed. Electron absorption spectrum of molecular form transforms gradually into the spectrum of the final form of dianion with titrant concentration increase. Determination of the coordinates of the inflection (and the corresponding concentration of DBU) on the titration curve  allowed us to distinguish two areas in the electron absorption spectra of the reaction system, which are likely belong to the first and second steps of deprotonation, namely, to the formation of mono- and dianionic forms (HP–  and P2–) of the compound. Spectral characteristics of the ionized forms and combined ionization constant for the first and second steps (lgКа1 and lgКа2) were revealed. At the first step in the order of decreasing acidic properties of the ligands the compounds form a series of: III< V< VIII< VI < VII< II< IV < I; at the second step in decreasing order of the acidic properties of the ligands the compounds form a series of:.III < V < VI < II <VIII< VII < IV < I. The effect of structural and electronic properties of substituents on acid-base properties of porphyrins is analyzed. Thus, chemical modification of the macrocycle can lead to direct changes in acid-base properties of supramolecular macroheterocyclic ligands and can be a powerful tool to control the reactivity of compounds of the porphyrins class.

Structural-Phase State of UFG-Titanium Implanted with Aluminum Ions

2020 ◽  
Vol 303 ◽  
pp. 161-168
Author(s):  
Alisa V. Nikonenko ◽  
Natalya A. Popova ◽  
E.L. Nikonenko ◽  
M.P. Kalashnikov ◽  
I.A. Kurzina
Keyword(s):  
Grain Size ◽  
Yield Stress ◽  
Phase State ◽  
Structural Phase ◽  
Ion Source ◽  
Anisotropy Factor ◽  
Structural Phase State ◽  
Aluminum Ions ◽  
Average Grain Size ◽  
Before And After

Transmission electron microscopy investigations were carried out to study the structural-phase state of ultra-fine grain (UFG) titanium with the average grain size of ~0.2 μm, implanted with aluminum ions. Implantation was carried out on MEVVA-V.RU ion source at room temperature, exposure time of 5.25 h and ion implantation dosage of 1⋅1018 ion/cm2. UFG-titanium was obtained by a combined multiple uniaxial compaction with rolling in grooved rolls and further annealing at 573 К for 1h. The specimens were investigated before and after implantation at a distance of 70-100 nm from the specimen surface. Concentration profile of aluminum implanted with α-Ti was obtained. It was revealed that the thickness of implanted layer was 200 nm, while maximum aluminum concentration was 70 at.%. Implantation of aluminum into titanium has resulted in formation of the whole number of phases having various crystal lattices, like β-Ti, TiAl3, Ti3Al, TiC and TiO2. The areas of their localization, the sizes, distribution density and volume fractions were determined. Grain distribution functions by their sizes were built, and the average grain size was defined. The paper investigates the influence of implantation on the grain anisotropy factor. It was revealed that implantation leads to the decrease in the average transverse and longitudinal grain size of α-Ti and decrease in the anisotropy factor by three times. The yield stress and contributions of separate strengthening mechanisms before and after implantation were calculated. The implantation has resulted in increase in the yield stress by two times.

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