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Comparison of optical spectra recorded during DPF-1000U plasma experiments with gas-puffing

Abstract

The results are presented of the optical spectra measurements for free plasma streams generated with the use of the modified DPF-1000U machine. This facility was recently equipped with a gas injection system (the so-called gas-puff) placed on the symmetry axis behind the central opening in the inner electrode. The DPF-1000U experimental chamber was filled up with pure deuterium at the initial pressure of 1.6 or 2.4 mbar. Additionally, when the use was made of the gas-puff system about 1 cm3 of pure deuterium was injected at the pressure of 2 bars. The gas injection was initiated 1.5 or 2 ms before the triggering of the main discharge. The investigated plasma discharges were powered from a condenser bank charged initially to 23 kV (corresponding to the energy of 352 kJ), and the maximum discharge current amounted to about 1.8 MA. In order to investigate properties of a dense plasma column formed during DPF-1000U discharges the use was made of the optical emission spectroscopy. The optical spectra were recorded along the line of sight perpendicular to the vacuum chamber, using a Mechelle®900 spectrometer. The recent analysis of all the recorded spectra made it possible to compare the temporal changes in the electron density of a freely propagating plasma stream for discharges without and with the gas-puffing. Using this data an appropriate mode of operation of the DPF-1000U facility could be determined.

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Synthesis and optical properties of CdSe/CdS core/shell nanocrystals

Abstract

This paper attempts to describe an effective method for producing a composite of quantum dots consisting of CdSe (core) with CdS (shell). This nanoparticles composite was synthesized from modified organometallic precursors. The sizes of the nanoparticles were estimated from X-ray diffraction data using Debye-Scherer formula and compared with high resolution electron microscopy (HRTEM) and optical spectra. The shape of CdSe/CdS NPs is nearly spherical and revels that the CdS shell with the thickness ~0.6 nm almost fully covers the CdSe core (higher contrast). Using UV-Vis spectroscopy, a systematic red shift in the absorption and emission spectra was observed after the deposition of CdS which confirms the shell growth over the CdSe core. In the CdSe/CdS core/shell structure, the holes are confined to the core, while the electrons are delocalized as a result of similar electron affinities of the core and the shell. The increased time of synthesis resulted in shell thickness increase. The observed properties of prepared CdSe/CdS QDs demonstrate the capability of the nanocomposite for using in the optoelectronics and photonics devices.

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Investigations of optical and surface properties of Ag single thin film coating as semitransparent heat reflective mirror

films caused non-reversible changes in their optical spectra and loosing protective properties. Extended surface morphology and surface states studies allowed us to find that the Ag thin film after exposition to heat radiation was transformed into Ag nano-islands, randomly distributed over the glass substrate surface. The sizes of observed islands determined from SEM and AFM investigations ranged mainly between 10 to 35 nm and 40 to 120 nm. XPS studies did not reveal any typical contaminations, as for example chlorine or sulfur, at the samples surface

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DFT study of optoelectronic spectra of barium cadmium chalcogenides (Ba2CdX3, X = S, Se and Te)

Abstract

DFT analyses of electronic and optical spectra of barium cadmium chalcogenides (Ba2CdX3, X = S, Se, Te) have been carried out. The study of electronic spectra has been made in terms of band structure and density of states using full potential linear augmented plane wave plus local orbital method. Band structure calculations have been carried out under the approximations PBE-GGA, PBE-Sol, LDA and TB-mBJ. Band structures of these materials show that Ba2CdS3, Ba2CdSe3 and Ba2CdTe3 crystals possess a band gap less than 1 eV, underestimated relative to the experimental/theoretical literature values. Optical spectra of these chalcogenides have been analyzed in terms of real and imaginary parts of dielectric function, reflectivity, refractive index, extinction coefficient, absorption coefficient, optical conductivity and electron energy loss. Optical results show large anisotropy along different directions. These results provide a physical basis of barium cadmium chalcogenides for potential application in optoelectronic devices.

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Model atmosphere analysis of two new early–type O4 dwarfs stars

Abstract

We present a synthetic spectra study of two new galactic early-type O4 dwarf stars(ALS 19618 and BD+50886) with high signal-to-noise ratio, typically S/N ∼ 300, medium-rosalution R ∼ 2500 optical spectra of O4 dwarfs stars from Galactic O-Stars Spectroscopic Survey (GOSSS), The main stellar parameters (Teff, surface gravity, rotational velocity) have been established using non-LTE, line-blanketed, atmospheric models calculated by TLUSTY204 and SYNSPEC49.

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First-principles study of electronic and optical properties of cubic perovskite CsSrF3

Abstract

We present first principles calculations of the electronic, structural and optical properties of the cubic perovskite CsSrF3 by using the full potential linearized augmented plane wave (FP-LAPW) plus local orbitals method with generalized gradient approximation (GGA) in the frame work of density functional theory. The calculated lattice constant is in a good agreement with the experimental result. The electronic band structure shows that the fundamental band gap is wide and direct at Γ point. The contribution of the different bands was analyzed from the total and partial density of states curves. The charge density plots show strong ionic bonding in Cs-F, ionic and weak covalent bonding between Sr and F. The calculated optical spectra viz., the dielectric function, optical reflectivity, absorption coefficient, real part of optical conductivity, refractive index, extinction coefficient and electron energy loss, are presented for the energy range of 0–30 eV.

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Research on interactions of plasma streams with CFC targets in the Rod Plasma Injector facility

Abstract

This paper present results of optical spectroscopy studies of interactions of intense plasma streams with a solid target made of carbon fibre composite (CFC). The experiments were carried out within the Rod Plasma Injector (RPI) IBIS facility. The optical measurements were performed first for a freely propagating plasma stream in order to determine the optimal operational parameters of this facility. Optical emission spectra (OES) were recorded for different operational modes of the RPI IBIS device, and spectral lines were identified originating from the working gas (deuterium) as well as some lines from the electrode material (molybdenum). Subsequently, optical measurements of plasma interacting with the CFC target were performed. In the optical spectra recorded with the irradiated CFC samples, in addition to deuterium and molybdenum lines, many carbon lines, which enabled to estimate erosion of the investigated targets, were recorded. In order to study changes in the irradiated CFC samples, their surfaces were analysed (before and after several plasma discharges) by means of scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS) techniques. The analysis of the obtained SEM images showed that the plasma irradiation induces noticeable changes in the surface morphology, for example vaporisation of some carbon fibres and formation of microcracks. The obtained EDS images showed that upon the irradiated target surface, some impurity ions are also deposited, particularly molybdenum ions from the applied electrodes.

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Heat treatment enhancement of natural orange-red sapphires

металлов в кристаллах. Наука, Москва, 1976. 5. Lehmann G., Harder H.: Optical spectra of di- and trivalent iron in corundum. The American Mineralogist, 55 (1970), 98-105. 6. Nikolskaya L. V., Terekhova V. M., Samoilovich M. I.: On the origin of natural sapphire color. Physics and Chemistry of Minerals, 3 (1978), 213-224. 7. Burns R.G.: Intervalence Transitions in Mixed Valence Minerals of Iron and Titanium. Annual Review of Earth and Planetary Sciences, 9 (1981), 345-383. 8. Fontana I., Le Donne A., Palanza

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Studies of plasma interactions with tungsten targets in PF-1000U facility

, M., Zielinska, E., & Makhlaj, V. A. (2015). Comparison of optical spectra recorded during DPF-1000U plasma experiments with gas-puffing. Nukleonika, 60(2), 309-314. DOI: 10.1515/nuka-2015-0058. 6. Skladnik-Sadowska, E., Malinowski, K., Sadowski, M. J., Wolowski, J., Gasior, P., Kubkowska, M., Rosinski, M., Marchenko, A. K., & Sartowska, B. (2009). Spectroscopy of the tungsten plasma produced by pulsed plasma-ion streams or laser beams. J. Nucl. Mater., 390/391, 847-851. DOI: 10.1016/j. jnucmat.2009.01.223.

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Optical properties of the plasma hydrogenated ZnO thin films

, TANGER Ltd.(2016). [6] Y.-Y. Chang, N. Neykova, J. Stuchlik, A. Purkrt, and Z. Remes, “Hydrogen Plasma Treatment of ZnO Thin Films”, NANOCON 2016 - 8th International Conference on Nanomaterials - Research and Application , Conference Proceedings, 8 vol. Hotel Voronez I, Brno, Czech Republic, TANGER Ltd.(2016). [7] J. Musil, P. Baroch, J. Vlček, K. H. Nam, and J. G. Han, “Reactive magnetron sputtering of thin films: present status and trends”, Thin Solid Films , vol 475 no. 1-2 (2005), 208-218. [8] J. Soucek, “Measurement and Modeling of Optical

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