Photoionization of Kr near the 4s threshold: IV. Photoionization through the autoionization of doubly-excited states

The photoionization cross sections for the production of the Kr II 4s state and Kr II satellite states were studied in the 4s ionization threshold region. The interference of direct photoionization and ionization through the autoionization decay of doubly-excited states was considered. In the calculations of doubly-excited state energies, performed by a configuration interaction technique, the 4p spin-orbit interaction and the (Kr II core)-(excited electron) Coulomb interaction were included. The theoretical cross sections are in many cases in good agreement with the measured values. Strong resonant features in the satellite spectra with threshold energies greater than 30 eV are predicted.

Relativistic effects in physics and chemistry of element 105. [Part] IV.

Results of relativistic (Dirac-Slater and Dirac-Fock) and nonrelativistic (Hartree-Fock-Slater) atomic and molecular calculations have been compared for the group 5 elements Nb, Ta, and Ha and their compounds MCl_5, to elucidate the influence of relativistic effects on their properties especially in going from the 5d element Ta to the 6d element Ha. The analysis of the radial distribution of the valence electrons of the metals for electronic configurations obtained as a result of the molecular calculations and their overlap with ligands show opposite trends in behavior for ns_1/2, np_l/2, and (n -1 )d_5/2 orbitals for Ta and Ha in the relativistic and nonrelativistic cases. Relativistic contraction and energetic stabilization of the ns_1/2 and np_l/2 wave functions and expansion and destabilization of the (n-1)d_5/2 orbitals make hahnium pentahalide more covalent than tantalum pentahalide and increase the bond strength. The nonrelativistic treatment of the wave functions results in an increase in ionicity of the MCl_5 molecules in going from Nb to Ha making element Ha an analog of V. Different trends for the relativistic and nonrelativistic cases are also found for ionization potentials, electronic affinities, and energies of charge-transfer transitions as well as the stability of the maximum oxidation state.

Observation of two-electron-one-photon transitions in silicon

We report on the observation of K\alpha\alpha X-rays of Si, produced in collisions of 15-28 MeV Si projectiles with various target atoms in the range Z =6 to 29. Energy shifts of X-rays were measured and are compared with theoretical predictions. Cross section ratios for emission of K\alpha\alpha and K\alpha radiation are given.

Molecular Beam Epitaxial Growth of III-V Semiconductor Nanostructures on Silicon Substrates

The main focus and concerns of this PhD thesis is the growth of III-V semiconductor nanostructures (Quantum dots (QDs) and quantum dashes) on silicon substrates using molecular beam epitaxy (MBE) technique. The investigation of influence of the major growth parameters on their basic properties (density, geometry, composition, size etc.) and the systematic characterization of their structural and optical properties are the core of the research work. The monolithic integration of III-V optoelectronic devices with silicon electronic circuits could bring enormous prospect for the existing semiconductor technology. Our challenging approach is to combine the superior passive optical properties of silicon with the superior optical emission properties of III-V material by reducing the amount of III-V materials to the very limit of the active region. Different heteroepitaxial integration approaches have been investigated to overcome the materials issues between III-V and Si. However, this include the self-assembled growth of InAs and InGaAs QDs in silicon and GaAx matrices directly on flat silicon substrate, sitecontrolled growth of (GaAs/In0,15Ga0,85As/GaAs) QDs on pre-patterned Si substrate and the direct growth of GaP on Si using migration enhanced epitaxy (MEE) and MBE growth modes. An efficient ex-situ-buffered HF (BHF) and in-situ surface cleaning sequence based on atomic hydrogen (AH) cleaning at 500 °C combined with thermal oxide desorption within a temperature range of 700-900 °C has been established. The removal of oxide desorption was confirmed by semicircular streaky reflection high energy electron diffraction (RHEED) patterns indicating a 2D smooth surface construction prior to the MBE growth. The evolution of size, density and shape of the QDs are ex-situ characterized by atomic-force microscopy (AFM) and transmission electron microscopy (TEM). The InAs QDs density is strongly increased from 108 to 1011 cm-2 at V/III ratios in the range of 15-35 (beam equivalent pressure values). InAs QD formations are not observed at temperatures of 500 °C and above. Growth experiments on (111) substrates show orientation dependent QD formation behaviour. A significant shape and size transition with elongated InAs quantum dots and dashes has been observed on (111) orientation and at higher Indium-growth rate of 0.3 ML/s. The 2D strain mapping derived from high-resolution TEM of InAs QDs embedded in silicon matrix confirmed semi-coherent and fully relaxed QDs embedded in defectfree silicon matrix. The strain relaxation is released by dislocation loops exclusively localized along the InAs/Si interfaces and partial dislocations with stacking faults inside the InAs clusters. The site controlled growth of GaAs/In0,15Ga0,85As/GaAs nanostructures has been demonstrated for the first time with 1 μm spacing and very low nominal deposition thicknesses, directly on pre-patterned Si without the use of SiO2 mask. Thin planar GaP layer was successfully grown through migration enhanced epitaxy (MEE) to initiate a planar GaP wetting layer at the polar/non-polar interface, which work as a virtual GaP substrate, for the GaP-MBE subsequently growth on the GaP-MEE layer with total thickness of 50 nm. The best root mean square (RMS) roughness value was as good as 1.3 nm. However, these results are highly encouraging for the realization of III-V optical devices on silicon for potential applications.

Squeezed thermal phonons precurse nonthermal melting of silicon as a function of fluence

A femtosecond-laser pulse can induce ultrafast nonthermal melting of various materials along pathways that are inaccessible under thermodynamic conditions, but it is not known whether there is any structural modification at fluences just below the melting threshold. Here, we show for silicon that in this regime the room-temperature phonons become thermally squeezed, which is a process that has not been reported before in this material. We find that the origin of this effect is the sudden femtosecond-laser-induced softening of interatomic bonds, which can also be described in terms of a modification of the potential energy surface. We further find in ab initio molecular-dynamics simulations on laser-excited potential energy surfaces that the atoms move in the same directions during the first stages of nonthermal melting and thermal phonon squeezing. Our results demonstrate how femtosecond-laser-induced coherent fluctuations precurse complete atomic disordering as a function of fluence. The common underlying bond-softening mechanism indicates that this relation between thermal squeezing and nonthermal melting is not material specific.

Adsorption kinetic investigations of phthalocyanine derivatives self assembled monolayers (SAMs) on gold: Temperature influence on the SAM formation process and quality

The ordered nano-structured surfaces, like self-assembled monolayers (SAMs) are of a great scientific interest, due to the low cost, simplicity, and versatility of this method. SAMs found numerous of applications in molecular electronics, biochemistry and optical devices. Phthalocyanine (Pc) complexes are of particular interest for the SAM preparation. These molecules exhibit fascinating physical properties and are chemically and thermally stable. Moreover their complex structure is advantageous for the fabrication of switchable surfaces. In this work the adsorption process of Pcs derivatives, namely, subphthalocyanines (SubPcB) and terbium (2TbPc) sandwich complexes on gold has been investigated. The influence of the molecular concentration, chain length of peripheral groups, and temperature on the film formation process has been examined using a number of techniques. The SAMs formation process has been followed in situ and in real time by means of second harmonic generation (SHG) and surface plasmon resonance (SPR) spectroscopy. To investigate the quality of the SAMs prepared at different temperatures atomic force microscopy (AFM) and X-Ray photoelectron spectroscopy (XPS)measurements were performed. Valuable information about SubPcB and 2TbPc adsorbtion process has been obtained in the frame of this work. The kinetic data, obtained with SHG and SPR, shows the best conformance with the first order Langmuir kinetic model. Comparing SHG and SPR results, it has been found, that the film formation occurs faster than the formation of chemical bonds. Such, the maximum amount of molecules on the surface is reached after 6 min for SubPcB and 30 min for 2TbPc. However, at this time the amount of formed chemicals bonds is only 10% and 40% for SubPcB and 2TbPc, respectively. The most intriguing result, among others, was obtained at T = 2 °C, where the formation of the less dense SAMs have been detected with SHG.However, analyzing XPS and AFM data, it has been revealed, that there is the same amount of molecules on the surface at both temperature T = 2 °C, and T = 21 °C, but the amount of formed chemicals bond is different. At T = 2 °C molecules form aggregates, therefore many of available anchor groups stay unattached.

Creaci??n de una p??gina web con motivo del IV centenario del Quijote

Se presenta memoria final de proyecto educativo que pretende fomentar la lectura y escritura entre el alumnado, a trav??s de la creaci??n de una p??gina web en honor al IV centenario de El Quijote. Se realiza en el IES Auringis en Ja??n. Los objetivos son: incentivar la participaci??n del profesorado en proyectos que superen el ??mbito exclusivo del centro, aprovechando las facilidades que proporcionan al respecto las nuevas tecnolog??as; habilitar foros donde el profesorado puedan compartir experiencias, buscar soluciones a problemas profesionales cotidianos, lanzar ideas; fomentar entre el alumnado el h??bito de lectura por medio del boca a boca, m??todo que, al menos por ahora, consideramos m??s efectivo que el de la imposici??n de lecturas obligatorias; propiciar que el alumnado cuenten la lectura como una posibilidad m??s de entre las que existen para ocupar el tiempo de ocio; luchar contra el prejuicio elitista que gira en torno a lo libresco; fomentar enfoques interdisciplinares del hecho de leer; festejar el IV centenario de la publicaci??n de la primera parte de El Quijote. El proceso consta: reuniones previas a la elaboraci??n del proyecto de innovaci??n; redacci??n del proyecto de innovaci??n; investigaciones tendentes a darle contenido a la p??gina web; encuentros con autores; premios literarios; exposiciones sobre autores y libros; lecturas p??blicas; asistencia a los actos conmemorativos; participaci??n en experiencias de 'Book-crossing'; feria del libro; redacci??n de la memoria de progreso; redacci??n de la memoria final. Los resultados obtenidos: p??gina web, exposiciones, encuentros con autores, premios literarios, feria del libro.

IV encuentro institucional del Consejo Escolar de la Regi??n de Murcia, Consejos Escolares Municipales y de Centro : la formaci??n de padres, un modelo de actuaci??n para la Regi??n de Murcia

El cuarto encuentro institucional del Consejo Escolar de la Regi??n de Murcia con los consejos municipales y de centro se dedic?? a la formaci??n de padres como protagonistas del proceso educativo de sus hijos. El libro recoge las intervenciones de los ponentes y un resumen de las 37 comunicaciones recibidas.

Congreso internacional de creatividad : espacios para la creatividad : IV encuentro de profesores e investigadores en el campo de la creatividad : la evaluaci??n de la creatividad. Libro de res??menes. Del 18 al 20 de septiembre de 2003, La Manga del Mar Menor

Incluye relaci??n de participantes con sus direcciones electr??nicas

IV Congreso Nacional de Escuelas Oficiales de Idiomas : diversidad, cultura y did??ctica de las lenguas

El IV Congresos de Escuelas Oficiales de Idiomas celebrado en Murcia en abril de 2005 bajo el lema: Diversidad, Cultura y Did??ctica de las Lenguas refleja las preocupaciones e inquietudes de un profesorado que se mueve entre la innovaci??n did??ctica, la tradicional relaci??n de los idiomas con la cultura, y los cambios derivados de la implantaci??n de los nuevos curr??culos de las ense??anzas y del creciente uso de las tecnolog??as de la informaci??n y comunicaci??n en las aulas..

Cuadernos para educar en el tercer milenio IV : [temas de reflexión y diálogo] : 2007.

Se recogen colaboraciones (artículos y aportaciones de colegios) de profesores, en cuanto a experiencias y reflexiones pedagógicas en torno a la escuela como espacio de ayuda e intercambio. Se alude a temas relacionados con la convivencia escolar, necesidad de adaptación del profesorado a las nuevas herramientas pedagógicas (TIC), responsabilidad de la función directiva en la escuela, resolución de conflictos y orientación y tutoría; además del análisis biográfico de Santa Joaquina de Vedruna, como ejemplo de labor pedagógica y educadora cristiana..

IV Jornada de Intercambio de Experiencias en Educaci??n para la Salud : Regi??n de Murcia

Las actas recogen la inauguraci??n, las ponencias, posters, comunicaciones y conclusiones, as?? como los actos de clausura de la jornada.

Oblique Angle Deposition of Germanium Film on Silicon Substrate

The effect of flux angle, substrate temperature and deposition rate on obliquely deposited germanium (Ge) films has been investigated. By carrying out deposition with the vapor flux inclined at 87° to the substrate normal at substrate temperatures of 250°C or 300°C, it may be possible to obtain isolated Ge nanowires. The Ge nanowires are crystalline as shown by Raman Spectroscopy.