Spelling suggestions: "subject:"[een] ALKALI HALIDE"" "subject:"[enn] ALKALI HALIDE""
1 |
The chemistry and electronic structure of surfaces of ionic compoundsWilliams, A. A. January 1985 (has links)
No description available.
|
2 |
Optical Absorption Spectra in the Theory of Alkali Halides containing H⁻ ionsGethins, Trevor 10 1900 (has links)
Optical absorption spectra of alkali halide crystals containing H⁻ ions (U-centres) are calculated using a two-parameter model to describe the defect. It is shown that this model gives a satisfactory account of the observed anharmonic sideband of the main U-centre absorption band in the infrared, and also of the impurity-induced far infrared absorption for the two host crystals considered, potassium bromide and potassium iodide. The broadening of localized modes and resonances is also discussed. In particular, the anharmonic broadening is calculated for the main U-centre line in KI and KBr and for a localized gap mode in KI:KH. / Thesis / Doctor of Philosophy (PhD)
|
3 |
Molecular-Level Understanding of Ionic Liquid/Solid Interfaces: Atomic Force Microscopy Study / 原子間力顕微鏡によるイオン液体/固体界面の分子レベル解析Bao, Yifan 25 March 2024 (has links)
京都大学 / 新制・課程博士 / 博士(工学) / 甲第25287号 / 工博第5246号 / 京都大学大学院工学研究科材料工学専攻 / (主査)教授 杉村 博之, 教授 邑瀬 邦明, 准教授 小林 圭 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM
|
4 |
Construção de um laser de centro de cor para aplicações em espectroscopia. / Development of a color center laser for spectroscopy application.Germano Woehl Junior 23 June 1986 (has links)
O objetivo deste trabalho é o desenvolvimento de um laser de centro de cor para aplicações em espectroscopia. O laser opera em regime CW e a cavidade óptica utilizada é do tipo X, com dois espelhos esféricos intracavidade astigmáticamente compensados. O meio ativo utilizado foi um cristal de KCl:Li+ com centros FA (II), e como fonte de bombeamento foi empregado um laser de Ar+ em 514nm. O limiar de potência de bombeamento foi de 120 mW, a eficiência energética foi de 2,8% e o intervalo de sintonia obtido vai de 2,56 a 2,82 μm numa potência de bombeamento de 700mW. O laser opera também com a cavidade na configuração anel. Para testar o LCC foram feitas aplicações empregando a técnica de espectroscopia intercavidade em cristais de KCl: Li+: NO-2: NO-3 e KBr:OH-. / The present work shows the development of a color Center laser for spectroscopy application. It is a CW laser which uses an X-type cavity with two astigmatically compensated intracavity spherical mirrors. The laser can be converted to a ring laser. The used active medium was a KCl:Li+ single crystal with a FA (II) centers and the pumping source was an Ar+ laser (λ= 514nm, 700mW). Pump power at threshold was measured to be 120mW. The tuning range was 2.56< λ < 2.82 μm and the slope efficiency was 2,8%. To test the color center laser we measured intracavity spectra of KCl: Li+: NO-2: NO-3 and KBr:OH- single crystals.
|
5 |
Multicomponent Clusters/Nanoparticles : An Investigation of Electronic and Geometric Properties by Photoelectron SpectroscopyZhang, Chaofan January 2013 (has links)
Clusters/nanoparticles are aggregates of a “small” number of building blocks, atoms or molecules, ranging from two up to millions of atoms. Two main groups of clusters have been studied using photoelectron spectroscopy based on synchrotron radiation. They are dry/wet alkali-halide clusters, including pure water clusters, and metal-based nanoparticles. For the dry alkali halide clusters, analysis of the data and theoretical modeling has allowed us insights into the local electronic properties at nanoscale: a change of polarizability of ions in the alkali-halide clusters due to the varying environment has been suggested. The study of the wet salt clusters shows that the alkali-halides are already solvated at the nanoscale reached by water clusters doped with salt vapor. The photoelectron angular distribution of water cluster shows lower anisotropy parameters as compared to the separate monomers. A model based on intracluster scattering has been built to partly explain the reduction. In the last part of the thesis, metal-based multi-component nanoparticles have been produced by self-assembly processes using reactive magnetron sputtering. Depending on the specific metal element, oxidation processes have been applied before or after the aggregation. Clearly radial distributions such as core-shell and “sandwich-like” structures have unambiguously determined by photoelectron spectroscopy.
|
6 |
[en] LASER INDUCED DESORPTION IN INSULIN, CARBON AND ALKALI HALIDES / [fr] DÉSORPTION IONIQUE INDUITE PAR LASER EN INSULINE, CARBONE ET HALOGÉNURES ALCALINS / [pt] DESSORÇÃO INDUZIDA POR LASER EM INSULINA, CARBONO E HALETOS ALCALINOSFRANCISCO ALBERTO FERNANDEZ LIMA 12 July 2006 (has links)
[pt] O fenômeno de dessorção iônica a partir da incidência de
pulsos de
radiação laser ultravioleta sobre superfícies em vácuo foi
estudada. A dessorção
de três tipos diferentes de sólidos foi analisada:
insulina, carbono (amorfo e
grafite) e policristais de haletos alcalinos. Os processos
fundamentais da interação
da radiação laser com sólido e o vapor formado, assim como
a evolução do
plasma gerado, foram descritos satisfatoriamente através
de um modelo térmico e
da simulação de espectros de têmpo-de-vôo para os
primeiros instante da
expansão ao vácuo. Um novo método foi proposto para
determinar as velocidades
iniciais e o início da expansão livre em função da
intensidade do laser para LDI
(Laser Desorption Ionization) e MALDI (Matrix Assisted
Laser Desorption
Ionization). Embora o estudo da expansão do plasma gerado
não tenha sido
tratada dinamicamente pela sua complexidade, a análise
utilizando varias
combinações do sólido irradiado permitiram concluir que a
dessorção induzida
por laser pode ser caracterizada por dois processos
fundamentais: i) a atomização
seguida de recombinação dos constituintes do alvo formando
aglomerados e ii) a
emissão de aglomerados pré-formados do material. As
estruturas geométricas
mais estáveis das espécies detectadas foram caracterizadas
utilizando a Teoria do
Funcional da Densidade (DFT) e classificadas
taxonomicamente em função de sua
energia (método D-plot); determinou-se a influência da
estabilidade dessas
estruturas nas abundâncias relativas no espectro de massa. / [en] Ion desorption induced by ultraviolet laser radiation
pulses was studied in
surfaces in vacuum. The ion desorption from three
different solids was analyzed:
insulin, carbon (amorphous and graphite) and polycrystals
of alkali halides. The
main processes involved in the laser-solid and laser-vapor
interactions, as well as
in the plasma evolution, were well described by a thermal
model and by the
simulation of the time-of-flight spectra for the first
moments of the plasma
expansion to vacuum. A new method to determine the initial
velocity and the
beginning of the free expansion regime as a function of
the laser intensity was
proposed for LDI (Laser Desorption Ionization) and MALDI
(Matrix Assisted
Laser Desorption Ionization). Considering the complexity
of the dynamical
treatment of the expansion of the laser-generated plasma,
an analysis by using
several combinations of irradiated solids was performed.
It was established that
the desorption process is characterized by two main
mechanisms: i) the
atomization followed by recombination of the target
elements in clusters and ii)
the emission of preformed clusters of the target material.
The most stable
geometric structures of the measured species were
characterized using Density
Functional Theory (DFT) and classified taxonomically as a
function of their
internal total energy (D-plot method); the influence of
the structure`s stability on
the relative mass abundances was also determined. / [fr] Le phénomène de la désorption ionique induite par des
pulses laser
ultraviolets dans la surface de solides est étudié. Trois
types différents de solides
ont été analysés: insuline, carbone (amorphe, graphite et
CO condensé) et
halogénures alcalins polycristallins (CsI, KI, KBr). La
dynamique des ions
secondaires émis est analysée par la comparaison des
résultats de modélisation
avec leur distributions de vitesse mesurées. Un modèle
thermique est proposé
pour décrire l´interaction entre la radiation laser avec
une pellicule de CsI
polycristallin et aussi avec la plume émise dans ce
processus. Dans le cadre de ce
modèle, une nouvelle méthode est utilisée pour
caractériser le régime de collision
dans lê plasma, soit dans le cas du LDI (Laser Desorption
Ionization), fait sur le
CsI, soit dans le cas du MALDI (Matrix Assisted Laser
Desorption Ionization),
fait sur l´insuline dissoute dans une solution solide d´
ACHC. Il est rappelé que le
ions CsI émis peuvent être reconstitués après une
atomisation complète de la cible
mais ceux des de l´insuline difficilement le peuvent. Pour
mieux comprendre
l´émission des agrégats ioniques Cn
+ et des halogénures alcalins, leurs structures
moléculaires ont été étudiées théoriquement par DFT
(Density Functional
Theory). L´énergie totale de chaque isomère a été calculée
et transformée dans
une nouvelle quantité nommée déviation énergétique (D). Le
graphique D-plot,
oú D est présenté en fonction du nombre de monomères, n,
s´est montré très utile
pour classer les agrégats en familles et pour estimer leur
stabilité, laquelle est liée
vraisemblablement à ses abondances de désorption.
|
7 |
Alkali-Halide Thin Films : Growth, Structure and Reactivity upon Electron Irradiation / Couches minces d'halogénures de métaux alcalins : structure et réactivité sous irradiation électroniqueHusseen, Ala 29 March 2018 (has links)
NaCl et KCl sont des matériaux à large bande interdite d’énergie, qui sont de plus en plus utilisés sous forme de couches minces en sciences des surfaces et dans des études de spectroscopie de molécules individuelles, pour découpler électroniquement des molécules organiques d’un substrat métallique. De plus, la réactivité de NaCl et KCl, sous forme de cristaux massifs, sous irradiation électronique ou photonique, a été beaucoup étudiée depuis les années 1970s. Dans ce mémoire de thèse, nous présentons les résultats d’une étude détaillée de couches minces de NaCl et de KCl sur Ag(001) par microscopie et spectroscopie à effet tunnel (STM/STS), diffraction des électrons lents (LEED) et spectroscopie d’électrons Auger (AES) sous ultravide. Afin d’obtenir des couches minces de haute qualité sur une surface métallique et de contrôler les propriétés de ces couches (épaisseur, taille et orientation des domaines, etc.), nous étudions en détails la formation de la couche en fonction des paramètres de croissance. De plus, les mesures de topographie STM montrent que l’épaisseur apparente et le contraste STM des couches isolantes dépendent de la différence de potentiel pointe-surface. Nous décrivons les modifications induites par irradiation électronique d’halogénures d’alcalins dans le régime de couches ultraminces. Les cinétiques et produits de réaction sont examinés dans le cas de couches de NaCl sur Ag(001). Les modifications structurales et chimiques sous faisceau d’électrons d’énergie 52-60 eV et 3 keV sont étudiées en utilisant respectivement le LEED et l’AES. Les effets de l’irradiation sur la géométrie et l’épaisseur des couches (allant de 2 à 5 couches atomiques) sont mesurés en STM. Nous observons que la déplétion en chlore induite par l’irradiation suit une cinétique différente de celles précédemment décrites pour les couches épaisses et cristaux massifs de NaCl. Les atomes de sodium produits par la dissociation de NaCl diffusent vers les zones nues de la surface Ag(001), où ceux-ci forment des superstructures Na-Ag connues pour le système Na/Ag(001). La modification des couches est le résultat de deux processus, pouvant être interprétés comme une désorganisation rapide de la couche avec l’arrachement de molécules de NaCl des bords d’îlots, et une perte lente de l’ordre structural à l’intérieur des îlots de NaCl due à la formation de trous par déplétion du chlore. La cinétique de la croissance des superstructures Na-Ag est expliquée par la diffusion limitée sur la surface irradiée, en raison de l’agrégation de molécules de NaCl désordonnées aux bords de marches du substrat. Nous avons également entrepris l’étude par STM de molécules de PTCDA déposées sur le substrat métallique Ag(001) et sur le système KCl/Ag(001). Nous obtenons une monocouche de PTCDA sur Ag(001) qui présente un arrangement avec une maille carrée. Sur les films de KCl, des molécules de PTCDA isolées ainsi que des structures empilées compactes ont été trouvées. / NaCl and KCl are wide band gap materials that are increasingly used as thin films in surface science and single-molecule spectroscopy studies to electronically decouple organic molecules from a metal substrate. In addition, the reactivity of bulk NaCl and KCl crystals under electron irradiation has been widely studied since the year 1970 s. In this dissertation, we report a detailed investigation on the structures of two different thin films of NaCl and KCl grown on the Ag(001) substrate by scanning tunneling microscopy (STM), scanning tunneling spectroscopy (STS), low energy electron diffraction (LEED), and Auger electron spectroscopy (AES) in ultrathin vacuum condition. In order to obtain high-quality thin films and to control the properties of these films on the metal surface (film thickness, domain size, domain orientation, etc), we study in detail the film growth, especially as a function of the growth parameters. In addition, the apparent height measurements by STM show that the apparent thickness and the STM contrast of these two insulating films are bias dependent. We report on an electron-induced modification of alkali halides in the ultrathin film regime. The reaction kinetics and products of the modifications are investigated in the case of NaCl films grown on Ag(001). Their structural and chemical modification upon irradiation with electrons of energy 52–60 eV and 3 keV is studied using LEED and AES, respectively. The irradiation effects on the film geometry and thickness (ranging from between two and five atomic layers) are examined using STM. We observe that Cl depletion follows different reaction kinetics, as compared to previous studies on thick NaCl films and bulk crystals. Na atoms produced from NaCl dissociation diffuse to bare areas of the Ag(001) surface, where they form Na-Ag superstructures that are known for the Na/Ag(001) system. The modification of the film is shown to proceed through two processes, which are interpreted as a fast disordering of the film with removal of NaCl from the island edges and a slow decrease of the structural order in the NaCl with formation of holes due to Cl depletion. The kinetics of the Na-Ag superstructure growth is explained by the limited diffusion on the irradiated surface, due to aggregation of disordered NaCl molecules at the substrate step edges. We have also investigated the deposition of PTCDA molecules on the metallic substrate Ag(001) and on the KCl/Ag(001) system using STM. We obtain a monolayer of PTCDA molecules on Ag(001) that is arranged in a square unit cell. On KCl films, both individual PTCDA molecules and a densely packed structure are found.
|
Page generated in 5.2346 seconds