Spelling suggestions: "subject:"spectroscopic"" "subject:"pectroscopic""
361 |
Étude théorique des molécules diatomiques BN, SiN et LaH, structure électronique et spectroscopie / Theoretical study of diatomic molecules BN, SiN and LaH, electronic structure and spectroscopyMahmoud, Salman 05 December 2014 (has links)
Une étude théorique ab initio des structures électroniques des molécules Diatomiques polaires BN, SiN et LaH dans la représentation 2s+1Λ(+/-)Ont été effectués par la méthode du champ auto-cohérent de l'espace Actif complet (CASSCF), suivie par l'interaction de la configuration multiréférence (MRSDCI). La correction de Davidson, notée (MRSDCI+ Q), a ensuite été appliquée pour rendre compte de clusters ou agrégats quadruples non liés. L'ensemble de l'espace de configuration de CASSCF a été utilisé comme référence dans le calcul MRCI, qui a été effectués en utilisant le programme de calcul de chimie physique MOLPRO et en tirant parti de l'interface graphique Gabedit. Quarante-deux de plus bas états électroniques dans la représentation 2s+1Λ(+/-)au-dessous de 95000 cm-1 ont été étudiés de la molécule BN. Alors que vingt-huit états électroniques dans les représentations 2s+1Λ(+/-) jusqu'à 70000 cm-1 de la molécule de SiN ont été étudiés. D'autre part, les vingt-quatre bas états électroniques de LaH dans les représentations 2s+1Λ(+/-) au-dessous de 70000 cm-1 ont été étudiées par deux méthodes différentes et en prenant en considération l'effet des spin-orbite de la molécule LaH et nous avons observé la division énergétique des huit états électroniques. Les courbes d'énergie potentielle ont été construites avec la fréquence co-harmonique ωe, la distance internucléaire de l'équilibre re, les constantes de rotation Be. L'énergie électronique par rapport à l'état fondamentale Te a été calculé pour les états électroniques considérés comme des BN, SiN et la molécule LaH respectivement. En utilisant l'approche des fonctions canoniques, les valeurs propres Ev, les constantes rotationnelles Bv, la constante de distorsion centrifuge Dv et les abscisses des points de retournement Rmin and Rmax ont été calculés pour les états électroniques au niveau de vibration v=51 pour LaH molécule. Dix-huit et neuf états électroniques ont été étudiées pour la molécule BN et SiN respectivement. Pour LaH, vingt-trois états électroniques de la molécule LaH et l'effet de spin-orbite de molécule LaH sont donnés ici pour la première fois. La comparaison avec les données expérimentales et théoriques pour la plupart des constantes calculées démontre une très bonne précision. Enfin, ces résultats devraient ainsi mener à des études expérimentales plus poussées pour ces molécules. Nos résultats ont été publiés dans le Canadian Journal of Chemistry, Journal of Quantitative Spectroscopy and Radiative Transfer, nous avons deux autres articles en préparation à soumettre. / In the present work a theoretical investigation of the lowest molecular states of BN, SiN and LaH molecule, in the representation 2s+1Λ(+/-), has been performed via complete active space self-consistent field method (CASSCF) followed by multireference single and double configuration interaction method (MRSDCI). The Davidson correction noted as (MRSDCI+Q) was then invoked in order to account for unlinked quadruple clusters. The entire CASSCF configuration space was used as a reference in the MRCI calculation which has been performed via the computational chemistry program MOLPRO and by taking advantage of the graphical user interface Gabedit. Forty-two singlet, triplet, and quintet lowest electronic states in the 2s+1Λ(+/-) representation below 95000 cm-1 have been investigated of the molecule BN. While twenty-eight electronic states in the representation2s+1Λ(+/-)up to 70000 cm-1 of the SiN molecule have been investigated.On the other hand the Twenty four low-lying electronic states of LaH in the representation 2s+1Λ(+/-) below 35000 cm-1 have been studied by two different methods and by taking into consideration the spin orbit effect of the molecule LaH we give in the energy splitting of the eight electronic states. The potential energy curves (PECs) together with the harmonic frequency ωe, the equilibrium internuclear distance re, the rotational constants Be and the electronic energy with respect to the ground state Te have been calculated for the considered electronic states of BN, SiN and LaH molecule respectively. Using the canonical functions approach, the eigenvalues Ev, the rotational constants Bv ,the centrifugal distortion constants Dv and the abscissas of the turning points Rmin and Rmax have been calculated for electronic states up to the vibrational level v =51 for LaH molecule.Eighteen and Nine electronic states have been investigated here for the first time for the molecules of BN and SiN respectively, while for LaH, news results are performed for twenty three electronic states of LaH molecule and the spin-orbit effect of LaH molecule is given here for the first time. A comparison with experimental and theoretical data for most of the calculated constants demonstrated a very good accuracy. Finally, we expect that the results of our work should invoke further experimental investigations for these molecules. Our results have been published in Canadian journal of chemistry, Journal of Quantitative Spectroscopy and Radiative Transfer and we have two other papers in preparation to submit.
|
362 |
Étude de la pré-formation de particules α dans les noyaux de 40Ca et d'40Ar par cassure nucléaire / Study of α clusters in 40Ca and 40Ar through nuclear break-upLefebvre, Laurent 20 September 2013 (has links)
Le noyau est un objet quantique complexe formé de protons et neutrons. Dans l'approche champ moyen, les nucléons sont considérés comme des particules indépendantes évoluant dans un potentiel moyen. Cependant dans certaines conditions, des nucléons peuvent se regrouper pour former des amas ou « clusters ».Pour comprendre ce phénomène de « clusters » dans les noyaux, nous avons étudié la structure dans l'état fondamental du 40Ca et de l'40Ar. En effet, des calculs théoriques tendent à montrer que les noyaux N = Z pourraient plus facilement adopter une structure en « clusters » que les noyaux N ≠ Z en raison d'un plus grand recouvrement des fonctions d'onde des neutrons et protons. Dans ce cas, l'émission de particules α par les noyaux N = Z sous l'effet du potentiel nucléaire attractif d'un noyau projectile, appelée « Towing-Mode » sera plus important que pour un noyau N ≠ Z. Dans ce but, nous avons réalisé une expérience au GANIL utilisant un faisceau d'40Ar à 35 MeV/A et une cible de 40Ca. Le spectromètre SPEG a permis d'identifier avec une très bonne résolution les ions lourds produits durant la réaction. Les détecteurs silicium MUST2 furent placés tout autour de la cible pour mesurer les particules α émises par la cible et le projectile et le prototype de calorimètre EXL fut utilisé pour la détection des photons de décroissance des noyaux résiduels d'36Ar et de 36S.Un modèle théorique basé sur la résolution de l'équation de Schrödinger dépendante du temps (TDSE) a été utilisé pour reproduire certains résultats expérimentaux comme les distributions angulaires. L'analyse des données a permis de reconstruire des spectres d'énergies d'excitation et des sections efficaces différentielles. De la comparaison entre ces distributions expérimentales et celles calculées par le modèle théorique, nous avons pu extraire des facteurs spectroscopiques Sα pour les deux noyaux d'intérêt. Les taux de « clusterisation » observés pour ces deux noyaux semblent indiquer que la structure en « clusters » n'est pas plus favorisée dans le 40Ca que dans l'40Ar. / Nuclei are complex self-bound systems formed by nucleons. Conjointly to a mean-field picture in which nucleons can be regarded as independent particles, few nucleons might self-organize into compact objects, called clusters, inside the nucleus. It is theoretically predicted that it should manifest itself most strikingly for N = Z nuclei close to the emission thresholds and has been studied extensively in this region. We propose to study α-clusterization in the ground state of the N = Z 40Ca nucleus and the N ≠ Z 40Ar nucleus. We have studied the nuclear break-up of 40Ca when the 40Ar projectile passes by. If α clusters are preformed in 40Ca, the probability of α-emission through nuclear break-up will be enhanced as compared to 40Ar N ≠ Z nuclei. The nuclear break-up of 40Ca was studied with an 40Ar beam produced at GANIL at 35 MeV/A. The SPEG spectrometer was used to detect the heavy projectile with accurate resolution. The MUST2 Silicon detectors were placed around the target to measure the emitted α and the EXL calorimeter prototype was used to identify the γ rays from the decay of the residual 36Ar and 36S.A theoretical approach based on Time-Dependent Schrödinger Equation (TDSE) theory has been used to reproduce some experimental results like angular distributions.From the data analysis, we reconstructed excitation energy spectra and angular distributions which are compared to TDSE theory to extract some spectroscopic factors Sα. These factors show that there is no more clusterization state in the ground state of the 40Ca than in the ground state of 40Ar.
|
363 |
Elektrické výboje ve vodných a organických roztocích / Electric discharges in water and organic solutionsKlímová, Edita January 2013 (has links)
This work is focused on study of electrical discharges in liquids, especially in water solutions. Generation of the discharge in water solutions leads to simultaneous effect of UV radiation, shock waves, electrical field and most importantly, chemically reactive species. This can be utilized in many applications such as sterilization, degradation of organic waste products, lithotripsy or other medical applications. The experimental part is concentrated on a diaphragm arrangement of the reaction system. This means that the reactor is divided into two electrode reservoirs connected only through a small orifice in a dielectric barrier. This barrier is made of Macor® non-porous ceramics with thickness of 1 mm, with the diameter of the orifice 0.6 mm, in the first part of work. In the second part, ShapalTM-M ceramics of thickness 1.0 mm and orifice diameter 0.6 mm was used. The experimental part is divided into two sections. For both, NaCl is chosen as an electrolyte to set the initial conductivity of the tested solutions to the value of 400 S/cm. Supplied direct voltage is regulated to attain power of 100 W in the system. In the first part, effect of addition of chosen alcohols (ethanol, isopropylalcohol and glycerol) on the efficiency of the discharge in their water solutions is studied. For this purpose, a special glass reactor was designed and constructed. The efficiency of the discharge is measured by a spectroscopic determination of concentration of complex formed by a titanium reagent and hydrogen peroxide, which is generated during the discharge. The results show no positive effect of addition of extra OH group to the reaction through the alcohols. The use of isopropylalcohol causes even a significant decrease in the amount of hydrogen peroxide generated. The subject of the second part is a comparison of effect of different electrode materials on the discharge. The efficiency is measured by the same method as in the first part. Materials chosen were stainless steel, platinum, aluminium, copper and carbon. Each material shows different hydrogen peroxide production rate under the same parameters. The most perspective material seems to be carbon, as an inert material, that can be expected not to initiate any decomposition of hydrogen peroxide. The least favourable appears to be copper. When used, no production of hydrogen peroxide was observed in one of the electrode parts of the reactor.
|
364 |
Studium optických a interferenčních jevů na tenkých vrstvách organických materiálů / Study of Optical Properties and Interference Phenomena on Thin Films of Organic McaterialsSchmiedová, Veronika January 2016 (has links)
Ph.D. thesis is focused on the study and determination of layer thickness and optical properties, such as the dispersion dependence of the refractive index of various materials prepared in the form of thin layer. In the first part of this work the theoretical findings in the field of spectroscopic ellipsometry are summarised. These findings are followed by the description and characterization of the light polarization, evaluation of experimental data and determination of the physical properties of studied materials. Experimental and result section of this work is devoted to the preparation and characterization of thin films of the studied materials: titanum dioxide (TiO2), new organic materials (MDMO-PPV, PCDTBT, PCBTDPP, PC60BM, PC70BM) and reduced graphene oxide (rGO). These were all selected with respect to their potential use in the organic photovoltaics.
|
365 |
Studium optických vlastností tenkých vrstev organických fotovoltaických článků / Study of optical properties of thin films of organic photovoltaic cellsČuboň, Tomáš January 2017 (has links)
This master´s thesis is focused on measurement of optical properties of thin layer of materials used in organic solar cells (OSC). The usage of graphene oxides and its reduced forms as parts of hole transport layer (HLT) in OSC were studied. At the beginning of the thesis, there is described basic theory necessary to understand the optical properties of thin layers. The thin layer deposition and reduction of GO are discussed too. The experimental part is aimed to the optical characterization of prepared thin films. The results from optical microscopy, UV-VIS spectroscopy, FT-IR spectroscopy and spectroscopic ellipsometry were obtained. At the end of the thesis, the results are concluded and compared with already published literature.
|
366 |
ADVANCES OF MID-INFRARED PHOTOTHERMAL MICROSCOPY FOR IMPROVED CHEMICAL IMAGINGChen Li (8740413) 22 April 2020 (has links)
<div>Vibrational spectroscopic imaging has become an emerging platform for chemical visualization of biomolecules and materials in complex systems. For over a century, both Raman and infrared spectroscopy have demonstrated the capability to recognize molecules of interest by harnessing the characteristic features from molecular fingerprints. With the recent development of hyperspectral vibrational spectroscopy imaging, which records the chemical information without sacrificing the spatial-temporal resolution, numerous discoveries has been achieved in the field of molecular and cellular biology. Despite the ability to provide complimentary chemical information to Raman-based approaches, infrared spectroscopy has not been extensively applied in routine studies due to several fundamental limitations: 1). the poor spatial resolution; 2). inevitable strong water absorption; 3). lack of depth resolution.</div><div>Mid-infrared photothermal (MIP) microscopy overcame all the above mentioned problems and for the first time, enabled depth-resolved in vivo infrared imaging of live cells, microorganisms with submicrometer spatial resolution. The development of epi-detected MIP microscopy further extends its application in pharmaceutical and materials sciences. With the deployment of difference frequency generation and other nonlinear optical techniques, the spectral coverage of the MIP microscopy was significantly enhanced to enable chemical differentiation in complex systems across the broad mid-infrared region. In addition to the efforts to directly improve the performance of MIP microscopy, a novel quantitative phase imaging approach based on polarization wavefront shaping via custom-designed micro-retarder arrays was developed to take advantage of the highly sensitive phase measurement in combination with the photothermal effect. Besides, the extended depth-of-field and multifocus imaging enabled by polarization wavefront shaping could both improve the performance of MIP microscopy for volumetric imaging.</div>
|
367 |
FAT AND SODIUM QUANTIFICATION AND CORRELATION BY MRSIAhmad Abdurahman M. Alhulail (8933363) 16 June 2020 (has links)
<p>Lipids and sodium (<sup>23</sup>Na) are two essential components of the
human body. They play a role in almost all biological systems. However, an
increase in their levels is associated with metabolic diseases. The elevation
of their contents can cause similar health disorders. Examples of prevalent
disorders that share an increase of musculoskeletal lipids and <sup>23</sup>Na
are hypertension and diabetes. However, the relationship between in vivo
lipid and sodium levels in pathophysiology has not been studied enough and
therefore is still unclear. Additionally, the available quantification methods to facilitate such
a study may not be practical. They are either invasive, not sensitive enough,
or require an impractical measurement time.</p>
<p>Therefore, in this work, our aims were to develop practical in
vivo methods to quantify the absolute sodium concentration as well as the
concentration of each lipid component individually, and to study the
correlation between them within the skeletal muscles.</p>
<p>Since lipids and <sup>23</sup>Na have different nuclear magnetic
resonance properties, their quantification by magnetic resonance (MR)
techniques face different challenges. Thus, we optimized different MR
spectroscopic imaging (MRSI) techniques for lipids and <sup>23</sup>Na. </p>
<p>Our proposed proton MRSI was able to provide eight lipid fat fraction
(FF) maps representing each musculoskeletal lipid component (fatty acid)
detected by our MRSI technique, and demonstrated a superior sensitivity compared to the conventional
MR imaging methods.</p>
<p>For <sup>23</sup>Na, our developed <sup>23</sup>Na-MRSI was able to
measure and map the absolute <sup>23</sup>Na concentration with values agreeing
with those reported previously in biopsy studies, and with a high repeatability
(CV < 6 %) within significantly shorter acquisition time compared to other
available techniques.</p>
<p> Finally,
the <sup>23</sup>Na concentration and the fat fractions of each lipid component
within healthy skeletal muscles were measured and correlated using our
developed MRSI methods. Our findings suggest a positive regional relationship between <sup>23</sup>Na
and lipids and negative correlation between <sup>23</sup>Na and BMI under
healthy conditions.</p>
|
368 |
Analyse et modélisation d’étoiles naines blanches de type DB dans le Sloan Digital Sky Survey et le relevé GaiaGenest-Beaulieu, Cynthia 04 1900 (has links)
No description available.
|
369 |
Chemistry of polynuclear transition-metal complexes in ionic liquidsAhmed, Ejaz, Ruck, Michael January 2011 (has links)
Transition-metal chemistry in ionic liquids (IL) has achieved intrinsic fascination in the last few years. The use of an IL as environmental friendly solvent, offers many advantages over traditional materials synthesis methods. The change from molecular to ionic reaction media leads to new types of materials being accessible. Room-temperature IL have been found to be excellent media for stabilising transition-metal clusters in solution and to crystallise homo- and heteronuclear transition-metal complexes and clusters. Furthermore, the use of IL as solvent provides the option to replace high-temperature routes, such as crystallisation from the melt or gas-phase deposition, by convenient room- or low-temperature syntheses. Inorganic IL composed of alkali metal cations and polynuclear transition-metal cluster anions are also known. Each of these areas will be discussed briefly in this contribution. / Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.
|
370 |
Spectroscopic ellipsometry for the in-situ investigation of atomic layer depositionsSharma, Varun 15 May 2014 (has links)
Aim of this student research project was to develop an Aluminium Oxide (Al2O3 ) ALD process from trimethylaluminum (TMA) and Ozone in comparison of two shower head designs. Then studying the detailed characteristics of Al2O3 ALD process using various measurement techniques such as Spectroscopic Ellipsometry (SE), x-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM). The real-time ALD growth was studied by in-situ SE. In-situ SE is very promising technique that allows the time-continuous as well as time-discrete measurement of the actual growth over an ALD process time. The following ALD process parameters were varied and their inter-dependencies
were studied in detail: exposure times of precursor and co-reactant as well as Argon purge times, the deposition temperature, total process pressure, flow dynamics of two different shower head designs. The effect of varying these ALD process parameters was studied by looking upon ALD cycle attributes. Various ALD cycle attributes are: TMA molecule adsorption (Mads ), Ligand removal (Lrem ), growth kinetics (KO3 ) and growth per cycle (GPC).:List of abbreviations and Symbols ........................XII
Lists of Figures and Tables ...................................XVIII
1 Introduction .......................................................1
I Theoretical Part ..................................................3
2 Alumina in electronic industry ............................5
3 Atomic Layer Deposition ....................................7
3.1 History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.2 Process definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.3 Benefits and limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.4 ALD growth mechanism of Aluminium oxide from TMA/O 3 . . . . . . . . 9
3.5 Growth kinetics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
3.6 Comparison of TMA/O3 and TMA/H2O – A literature survey . . . . 14
4 Spectroscopic Ellipsometry .....................................................17
4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
4.2 Measuring Principle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
4.3 Fitting and models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
4.4 Advantages and limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
5 X-Ray Photoelectron Spectroscopy ..............................................25
5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
5.2 XPS mechanism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
5.3 XPS analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
5.4 Advantages and limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
6 Atomic Force Microscopy .............................................................29
II Experimental Part ......................................................................31
7 Methodologies ............................................................................33
7 .1 Experimental setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
7 .2 ALD process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
7 .3 Experiment design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
7 .4 Spectroscopic Ellipsometry . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
7 .4.1 Tool and software . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
7 .4.2 Data acquisition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
7 .4.3 Data evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
7 .4.4 Post processing of data . . . . . . . . . . . . . . . . . . . . . . . . . 41
7 .4.5 Sources of errors in SE . . . . . . . . . . . . . . . . . . . . . . . . . 43
8 Results and discussion ..........................................................47
8.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
8.2 Kinetic ALD characteristic curves . . . . . . . . . . . . . . . . . . . . . . . . 48
8.2.1 TMA exposure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
8.2.2 Argon purging after TMA exposure . . . . . . . . . . . . . . . . . . . 50
8.2.3 Ozone exposure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
8.2.4 Argon purging after ozone exposure . . . . . . . . . . . . . . . . . . 52
8.3 Impact of process parameters on characteristic ALD growth attributes and film properties . . . . . . . . . .. . . . . . . . . . . . . . . . 53
8.3.1 Total process pressure . . . . . . . . . . . . . . . . . . . . . . . . . . 53
8.3.2 Ozone flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
8.3.3 Deposition temperature . . . . . . . . . . . . . . . . . . . . . . . . . 56
8.4 Reproducibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
9 Conclusions and outlook .......................................................63
References ...............................................................................68
III Appendix .............................................................................77
A Reference temperatures and ozone flow.............................. 79
B Process parameters ..............................................................81
|
Page generated in 0.0351 seconds