Acid-base and Electron Donor Properties of Pr6O11 and Its Mixtures with Alumina

The electron donor properties of Pr6O11 activated at 300. 500 and 800°C are reported from the studies on adsorption of electron acceptors of various electron affinity (7. 7, 8, 8-tetracyanoquinodimethane. 2, 3. 5, 6-tetrachloro-l, 4-benzoquin one. p-dinitrobenzene. and m-dinitrobenzene) in three solvents (acetonitrile, 1,4-dioxan and ethyl acetate). The extent of electron transfer during adsorption is understood from magnetic measurements and ESR spectral data. The corresponding data on mixed oxides of Pr and Al are reported for various compositions, The acid / base properties of these oxides are determined using a set of Hammett indicators.

Surface electron properties and catalytic activity of Sr doped lanthana

The electron donating properties, surface acidity/basicity and catalytic activity of lanthana for various dopant concentrations of strontium are reported at two activation temperatures. The catalytic activity has been correlated with electron donating properties and surface acidity/basicity of the oxide.

Temporal and Spatial Behavior of Electron Density and Temperature in a Laser-Produced Plasma from YBa2Cu3O7

Spectroscopic studies of laser -induced plasma from a high-temperature superconducting material, viz., YBa2Cu3O7 (YBCO), have been carried out. Electron temperature and electron density measurements were made from spectral data. The Stark broad ening of emission lines was used to determine the electron density, and the ratio of line in tensities was exploited for the determination of electron temperature. An initial electron temperature of 2.35 eV and electron density of 2.5 3 1017 cm2 3 were observed. The dependence on electron temperature and density on different experimental parameters such as distance from the target, delay time after the in itiation of the plasm a, and laser irradiance is also discussed in detail. Index Headings: Laser -plasma spectroscopy; Plasma diagnostics; Emission spectroscop y; YBa2Cu3O7.

Prompt electron emission and collisional ionization of ambient gas during pulsed laser ablation of silver

A silver target kept under partial vacuum conditions was irradiated with focused nanosecond pulses at 1:06 mm from a Nd:YAG laser. The electron emission monitored with a Langmuir probe shows a clear twin-peak distribution. The first peak which is very sharp has only a small delay and it indicates prompt electron emission with energy as much as 60 5 eV. Also the prompt electron emission shows a temporal profile with a width that is same as that for the laser pulse whereas the second peak is broader, covers several microseconds, and represents the low-energy electrons (2 0:5 eV) associated with the laser-induced silver plasma as revealed by time-of-flight measurements. It has been found that prompt electrons ejected from the target collisionally excite and ionize ambient gas molecules. Clearly resolved rotational structure is observed in the emission spectra of ambient nitrogen molecules. Combined with time-resolved spectroscopy, the prompt electrons can be used as excitation sources for various collisional excitation–relaxation experiments. The electron density corresponding to the first peak is estimated to be of the order of 1017 cm?--3 and it is found that the density increases as a function of distance away from the target. Dependence of probe current on laser intensity shows plasma shielding at high laser intensities.

Twin peak distribution of electron emission profile and impact ionization of ambient molecules during laser ablation of silver target

Laser-induced plasma generated from a silver target under partial vacuum conditions using the fundamental output of nanosecond duration from a pulsed Nd:yttrium aluminum garnet laser is studied using a Langmuir probe. The time of flight measurements show a clear twin peak distribution in the temporal profile of electron emission. The first peak has almost the same duration as the laser pulse while the second lasts for several microseconds. The prompt electrons are energetic enough ('60 eV) to ionize the ambient gas molecules or atoms. The use of prompt electron pulses as sources for electron impact excitation is demonstrated by taking nitrogen, carbon dioxide, and argon as ambient gases.

Time evolution of the electron density and temperature in laser-produced plasmas from YBa2Cu3O7

Laser radiation at 1.06 µm from a pulsed Nd:YAG laser was focused onto a multielement YBa2Cu3O7 target in vacuum and the plasma thus generated was studied using time-resolved spectroscopic techniques. Line broadening of the Ba I emission line at 553.5 nm was monitored as a function of time elapsed after the incidence of a laser pulse on the target. Measured line profiles of barium species were used to infer the electron density and temperature, and the time evolution of these important plasma parameters has been worked out.

Electron density and temperature measurements in a laser produced carbon plasma

Plasma generated by fundamental radiation from a Nd:YAG laser focused onto a graphite target is studied spectroscopically. Measured line profiles of several ionic species were used to infer electron temperature and density at several sections located in front of the target surface. Line intensities of successive ionization states of carbon were used for electron temperature calculations. Stark broadened profiles of singly ionized species have been utilized for electron density measurements. Electron density as well as electron temperature were studied as functions of laser irradiance and time elapsed after the incidence of laser pulse. The validity of the assumption of local thermodynamic equilibrium is discussed in light of the results obtained.

Dielectric Properties of Electron Beam Evaporated Samarium Oxide Films

The dielectric properties of electron beam evaporated Sm2O3 films have been investigated in the frequency range from 1 kHz to 1 MHz at various temperatures (300 K-453 K). The dielectric constant is found to depend on film thickness and it attains a constant value beyond 1000 A. The present electron beam evaporated Sm2O3 films have a high dielectric constant of 43. The frequency dependence of and tan teeta at various temperatures is also studied.

Electron-Phonon Interaction Within the Framework of the Fluctuating Valence of Copper Atoms — a Theoretical Model for High Temperature Superconductivity

Electron-phonon interaction is considered within the framework of the fluctuating valence of Cu atoms. Anderson's lattice Hamiltonian is suitably modified to take this into account. Using Green's function technique tbe possible quasiparticle excitations' are determined. The quantity 2delta k(O)/ kB Tc is calculated for Tc= 40 K. The calculated values are in good agreement with the experimental results.

Electron Density Determination of Laser Induced Plasma from Polymethyl Methacrylate Using Phaseshift Detection Technique

Irradiation of a Polymethyl methacrylate target using a pulsed Nd-YAG laser causes plasma formation in the vicinity of the target. The refractive index gradient due to the presence of the plasma is probed using phase-shift detection technique. The phase-shift technique is a simple but sensitive technique for the determination of laser ablation threshold of solids. The number density of laser generated plasma above the ablation threshold from Polymethyl methacrylate is calculated as a function of laser fluence. The number density varies from 2×1016 cm-3 to 2×1017 cm-3 in the fluence interval 2.8-13 J · cm-2.

Geometric Algebra and Einstein’s Electron

This thesis entitled Geometric algebra and einsteins electron: Deterministic field theories .The work in this thesis clarifies an important part of Koga’s theory.Koga also developed a theory of the electron incorporating its gravitational field, using his substitutes for Einstein’s equation.The third chapter deals with the application of geometric algebra to Koga’s approach of the Dirac equation. In chapter 4 we study some aspects of the work of mendel sachs (35,36,37,).Sachs stated aim is to show how quantum mechanics is a limiting case of a general relativistic unified field theory.Chapter 5 contains a critical study and comparison of the work of Koga and Sachs. In particular, we conclude that the incorporation of Mach’s principle is not necessary in Sachs’s treatment of the Dirac equation.

Surface electron properties and catalytic activity of rare earth oxides

The rare earths have provided fascinating field for chemists confronted with problems of their separation and purification. The rare earths become available in relatively pure form in recent years due to the development of efficient separation methods, largely as a byproduct of the atomic energy programmes of various countries. The rare earths often called lanthanides from La (Z=57) to Lu (Z=7l) display subtle variation of properties through the series, while the differences become appreciable for the elements that are farther apart.

Acid-Base. Surface Electron Donatin6 &.Catai.Ytlc Properties Of Some Binary Mixed Oxides Containing Rare Earth Elements

Catalysis research underpins the science of modern chemical processing and fuel technologies. Catalysis is commercially one of the most important technologies in national economies. Solid state heterogeneous catalyst materials such as metal oxides and metal particles on ceramic oxide substrates are most common. They are typically used with commodity gases and liquid reactants. Selective oxidation catalysts of hydrocarbon feedstocks is the dominant process of converting them to key industrial chemicals, polymers and energy sources.[1] In the absence of a unique successfiil theory of heterogeneous catalysis, attempts are being made to correlate catalytic activity with some specific properties of the solid surface. Such correlations help to narrow down the search for a good catalyst for a given reaction. The heterogeneous catalytic performance of material depends on many factors such as [2] Crystal and surface structure of the catalyst. Thermodynamic stability of the catalyst and the reactant. Acid- base properties of the solid surface. Surface defect properties of the catalyst.Electronic and semiconducting properties and the band structure. Co-existence of dilferent types of ions or structures. Adsorption sites and adsorbed species such as oxygen.Preparation method of catalyst , surface area and nature of heat treatment. Molecular structure of the reactants. Many systematic investigations have been performed to correlate catalytic performances with the above mentioned properties. Many of these investigations remain isolated and further research is needed to bridge the gap in the present knowledge of the field.

Formation of carbon-encapsulated metallic nano-particles from metal acetylides by electron beam irradiation

Transition metal acetylides, MC2 (M=Fe, Co and Ni), exhibit ferromagnetic behavior of which TC is characteristic of their size and structure. CoC2 synthesized in anhydrous condition exhibited cubic structure with disordered C2− 2 orientation. Once being exposed to water (or air), the particles behave ferromagnetically due to the lengthening of the Co–Co distance by the coordination of water molecules to Co2+ cations. Heating of these particles induces segregation of metallic cores with carbon mantles. Electron beam or 193 nm laser beam can produce nanoparticles with metallic cores covered with carbon mantles

Ground and Excited State Electron Transfer Reaction Between a few Anthracene Appended Tertiary Amines and Suitable Electron Acceptors

the thesis entitled “Ground and Excited State Electron Transfer Reaction Between a few Anthracene Appended Tertiary Amines and Suitable Electron Acceptors” portrays our attempts to explore the solvent, concentration and temperature effect of the reaction between a few (anthracen-9- yl)methanamines with electron acceptors like DMAD, DBA and DBE. We have also studied the effect of solvent and percentage fluorescence quenching in the photoinduced electron transfer reactions of these ‘donor-spacer-acceptor’ systems. Finally we look in to the intramolecular electron transfer reactions of a few tertiary amine appended dibenzobarrelenes and bisdibenzobarrelenes