Variational Monte Carlo study of core-valence separation schemes for first-row atoms and positive ions /

All-electron partitioning of wave functions into products ^core^vai of core and valence parts in orbital space results in the loss of core-valence antisymmetry, uncorrelation of motion of core and valence electrons, and core-valence overlap. These effects are studied with the variational Monte Carlo method using appropriately designed wave functions for the first-row atoms and positive ions. It is shown that the loss of antisymmetry with respect to interchange of core and valence electrons is a dominant effect which increases rapidly through the row, while the effect of core-valence uncorrelation is generally smaller. Orthogonality of the core and valence parts partially substitutes the exclusion principle and is absolutely necessary for meaningful calculations with partitioned wave functions. Core-valence overlap may lead to nonsensical values of the total energy. It has been found that even relatively crude core-valence partitioned wave functions generally can estimate ionization potentials with better accuracy than that of the traditional, non-partitioned ones, provided that they achieve maximum separation (independence) of core and valence shells accompanied by high internal flexibility of ^core and Wvai- Our best core-valence partitioned wave function of that kind estimates the IP's with an accuracy comparable to the most accurate theoretical determinations in the literature.

Pr��paration d'��chantillons pour l'��tude par GISAXS des m��canismes de d��formation des mat��riaux par faisceaux d'ions lourds de haute ��nergie.

Le m��canisme menant �� des d��formations structurales suivant le bombardement d'��chantillons de a-Si d'un faisceau d'ions lourds et rapides est sujet de controverses. Nous nous sommes pench��s sur l'hypoth��se de la formation d'une zone liquide caus��e par la d��position d'��nergie des ions incidents dans le contexte de la th��orie du pic thermique. Des ��chantillons de silicium amorphe furent pr��par��s dans le but d'observer les indices d'une transition de phase l-Si/a-Si suivant la d��position locale d'��nergie sur le parcours d'un ion lourd ��nerg��tique dans le a-Si. Les ��chantillons furent implant��s d'impuret��s de Cu ou d'Ag avant d'��tre expos��s �� un faisceau d'ions Ag12+ de 70 MeV. L'utilisation de l'analyse GISAXS est projet��e afin d'observer une concentration locale d'impuret��s suivant leur s��gr��gation sur la trace de l'ion. Des masques d'implantation nanom��triques d'oxide d'aluminium ont ��t�� fabriqu��s afin d'augmenter la sensibilit�� de l'analyse GISAXS et une m��thode d'alignement de ces masques selon la direction du faisceau fut d��velopp��e. Le bombardement d'��chantillons au travers de ces masques a donn�� lieu �� un r��seau de sites d'impacts isol��s presque ��quidistants.

Fabrication Of Potentiometric Sensors For The Determination Of Certain Metal Ions

In this study Fabrication of Potentiometric sensors for the determination of certain metal ions, presents the synthesis and characterization of seven ionophores, their use in the fabrication of potentiometric sensors and the results and discussion of fourteen sensors developed for the determination of five transition metal ions. As part of the present investigations a total of fourteen potentiometric sensors have been developed and fabricated. A three fold approach has been taken in developing he sensors, PVC plasticized membrane sensor, carbon paste electrode and chemically modified carbon paste electrode. All the sensors are highly useful in the determination of metal ions such as manganese, nickel, copper, mercury and lead. A through analytical study has been carried out with respect to each other developed. Based on these studies, optimum conditions have been developed for the quantitative determinations of the selected metal ions using the sensors. Systematic application studies have also been carried out for all the developed sensors and the results revealed that the presently developed sensors are far superior than most of the sensors reported.

A PVC plasticized membrane sensor for nickel ions

A new PVC membrane sensor, which is highly selective towards Ni (II) ions, has been developed using a thiophene-derivative Schiff base as the ionophore. The best performance was exhibited by the membrane having the composition percentage ratio of 5:3:61:31 (ionophore:NaTPB:DBP:PVC) (w=w), where NaTPB is the anion excluder, sodium tetraphenylborate and DBP is the plasticizing agent (dibutyl phthalate). The membrane exhibited a good Nernstian response for nickel ions over the concentration range of 1.0 10 1��� 5.0 10 6M (limit of detection is 1.8 10 6 M) with a slope of 29.5 1.0mV per decade of activity. It has a fast response time of<20 s and can be used for a period of 4 months with good reproducibility. The sensor is suitable for use in aqueous solutions of a wide pH range of 3.2���7.9. The sensor shows high selectivity to nickel ions over a large number of mono-, bi- and trivalent cations. It has been successfully used as an indicator electrode in the potentiometric titration of nickel ions against EDTA and also for direct determination of nickel content in real samples ��� wastewater samples from electroplating industries and Indian chocolates.

A PVC Plasticized Membrane Sensor for Nickel Ions

A new PVC membrane sensor, which is highly selective towards Ni (II) ions, has been developed using a thiophene-derivative Schiff base as the ionophore. The best performance was exhibited by the membrane having the composition percentage ratio of 5:3:61:31 (ionophore:NaTPB:DBP:PVC) (w=w), where NaTPB is the anion excluder, sodium tetraphenylborate and DBP is the plasticizing agent (dibutyl phthalate). The membrane exhibited a good Nernstian response for nickel ions over the concentration range of 1.0 10 1��� 5.0 10 6M (limit of detection is 1.8 10 6 M) with a slope of 29.5 1.0mV per decade of activity. It has a fast response time of<20 s and can be used for a period of 4 months with good reproducibility. The sensor is suitable for use in aqueous solutions of a wide pH range of 3.2���7.9. The sensor shows high selectivity to nickel ions over a large number of mono-, bi- and trivalent cations. It has been successfully used as an indicator electrode in the potentiometric titration of nickel ions against EDTA and also for direct determination of nickel content in real samples ��� wastewater samples from electroplating industries and Indian chocolates.

Synthesis and Characterization of Some Organic Semiconductors and Investigations on the Effect of Swift Heavy Ions on Their Properties

In this work polymers belonging to polyaniline and polyaniline doped with camphor sulphonic acid are synthesised. Cobalt phthalocyanine is an interesting candidate belonging to the tetramers. Studies on the composites containing cobalt phthalocyanine tetramer and polyaniline doped with camphor sulphonic acid for various concentration are also undertaken in order to understand the mechanism. RF plasma polymerised aniline and furfural are prepared. The structural and electrical properties are evaluated. The bombardment of swift heavy ions of these films are carried out and the effect of irradiation on their properties is also investigated.

Catalysis by some metal oxides modified with phosphate ions

Surface acidity of phosphate modified La2O3,CeO2 and SnO2 has been estimated by titrimetric Method using Hammett Indicators.Mixed Oxides of tin and lanthanum have also been prepared and subjected to phosphate modification.Surface characterizartion of the samples has been carried out using XRD, surface area,thermal analysis and IR spectroscopy. Phosphate content in the samples has been chemically estimated. The catalytic activity for benzylation and esterification reaction has also been investigated.

Fabrication of Potentiometric Sensors for the Determination of Lanthanide Ions

In many fields such as earth science biology, environment and electronics, the knowledge about elemental distributions and chemical speciation is important. The determination of metal levels especially the toxic ones both in the environment and in biological materials are increasingly demanded by the society.Ion selective sensors have become one of the most effective ad powerful means for analytical scientists for the trace level monitoring of metal ions. The wide range of applications ,low material requirements and simplicity of analytical procedure have not only brought ion-selective electrodes in to the lime light of analytical chemistry,but have promoted their use as tools for physiologists,medical researchers,biologists,geologists,environmental protection specialists etc.Potentiometric ion-selective sensors have been developed for the determination of lanthanide ions such as La3+,Nd3+,Pr3+,Sm3+, and Gd3+.The sensors fabricated include both PVC membrane sensor and chemically modified carbon paste sensor. A set of 10 sensors have been developed. The response parameters of all the sensors have been studied and the sensors were applied as an indicator electrode in the potentiometric titration and for the determination of metal ions in real samples.

Studies on the optical band gap and cluster size of the polyaniline thin films irradiated with swift heavy Si ions

Polyaniline thin films prepared by RF plasma polymerisation were irradiated with 92MeV Si ions for various fluences of 1 1011, 1 1012 and 1 1013 ions/cm2. FTIR and UV���vis���NIR measurements were carried out on the pristine and Si ion irradiated polyaniline thin films for structural evaluation and optical band gap determination. The effect of swift heavy ions on the structural and optical properties of plasma-polymerised aniline thin film is investigated. Their properties are compared with that of the pristine sample. The FTIR spectrum indicates that the structure of the irradiated sample is altered. The optical studies show that the band gap of irradiated thin film has been considerably modified. This has been attributed to the rearrangement in the ring structure and the formation of CRC terminals. This results in extended conjugated structure causing reduction in optical band gap

Polarization and correlation phenomena in the radiative electron capture by bare highly-charged ions

In dieser Arbeit wird die Wechselwirkung zwischen einem Photon und einem Elektron im starken Coulombfeld eines Atomkerns am Beispiel des radiativen Elektroneneinfangs beim Sto�� hochgeladener Teilchen untersucht. In den letzten Jahren wurde dieser Ladungsaustauschprozess insbesondere f��r relativistische Ion���Atom���St����e sowohl experimentell als auch theoretisch ausf��hrlich erforscht. In Zentrum standen dabei haups��chlich die totalen und differentiellen Wirkungsquerschnitte. In neuerer Zeit werden vermehrt Spin��� und Polarisationseffekte sowie Korrelationseffekte bei diesen Sto��prozessen diskutiert. Man erwartet, dass diese sehr empfindlich auf relativistische Effekte im Sto�� reagieren und man deshalb eine hervorragende Methode zu deren Bestimmung erh��lt. Dar��ber hinaus k��nnten diese Messungen auch indirekt dazu f��hren, dass man die Polarisation des Ionenstrahls bestimmen kann. Damit w��rden sich neue experimentelle M��glichkeiten sowohl in der Atom��� als auch der Kernphysik ergeben. In dieser Dissertation werden zun��chst diese ersten Untersuchungen zu den Spin���, Polarisations��� und Korrelationseffekten systematisch zusammengefasst. Die Dichtematrixtheorie liefert hierzu die geeignete Methode. Mit dieser Methode werden dann die allgemeinen Gleichungen f��r die Zweistufen���Rekombination hergeleitet. In diesem Prozess wird ein Elektron zun��chst radiativ in einen angeregten Zustand eingefangen, der dann im zweiten Schritt unter Emission des zweiten (charakteristischen) Photons in den Grundzustand ��bergeht. Diese Gleichungen k��nnen nat��rlich auf beliebige Mehrstufen��� sowie Einstufen���Prozesse erweitert werden. Im direkten Elektroneneinfang in den Grundzustand wurde die ���lineare��� Polarisation der Rekombinationsphotonen untersucht. Es wurde gezeigt, dass man damit eine M��glichkeit zur Bestimmung der Polarisation der Teilchen im Eingangskanal des Schwerionensto��es hat. Rechnungen zur Rekombination bei nackten U92+ Projektilen zeigen z. B., dass die Spinpolarisation der einfallenden Elektronen zu einer Drehung der linearen Polarisation der emittierten Photonen aus der Streuebene heraus f��hrt. Diese Polarisationdrehung kann mit neu entwickelten orts��� und polarisationsempfindlichen Festk��rperdetektoren gemessen werden. Damit erh��lt man eine Methode zur Messung der Polarisation der einfallenden Elektronen und des Ionenstrahls. Die K���Schalen���Rekombination ist ein einfaches Beispiel eines Ein���Stufen���Prozesses. Das am besten bekannte Beispiel der Zwei���Stufen���Rekombination ist der Elektroneneinfang in den 2p3/2���Zustand des nackten Ions und anschlie��endem Lyman���1���Zerfall (2p3/2 ! 1s1/2). Im Rahmen der Dichte���Matrix���Theorie wurden sowohl die Winkelverteilung als auch die lineare Polarisation der charakteristischen Photonen untersucht. Beide (messbaren) Gr����en werden betr��chtlich durch die Interferenz des E1���Kanals (elektrischer Dipol) mit dem viel schw��cheren M2���Kanal (magnetischer Quadrupol) beeinflusst. F��r die Winkelverteilung des Lyman���1 Zerfalls im Wasserstoff�����hnlichen Uran f��hrt diese E1���M2���Mischung zu einem 30%���Effekt. Die Ber��cksichtigung dieser Interferenz behebt die bisher vorhandene Diskrepanz von Theorie und Experiment beim Alignment des 2p3/2���Zustands. Neben diesen Ein���Teichen���Querschnitten (Messung des Einfangphotons oder des charakteristischen Photons) wurde auch die Korrelation zwischen den beiden berechnet. Diese Korrelationen sollten in X���X���Koinzidenz���Messungen beobbachtbar sein. Der Schwerpunkt dieser Untersuchungen lag bei der Photon���Photon���Winkelkorrelation, die experimentell am einfachsten zu messen ist. In dieser Arbeit wurden ausf��hrliche Berechnungen der koinzidenten X���X���Winkelverteilungen beim Elektroneneinfang in den 2p3/2���Zustand des nackten Uranions und beim anschlie��enden Lyman���1�����bergang durchgef��hrt. Wie bereits erw��hnt, h��ngt die Winkelverteilung des charakteristischen Photons nicht nur vom Winkel des Rekombinationsphotons, sondern auch stark von der Spin���Polarisation der einfallenden Teilchen ab. Damit er��ffnet sich eine zweite M��glichkeit zur Messung der Polaristion des einfallenden Ionenstrahls bzw. der einfallenden Elektronen.

Auger spectroscopy of foil-excited beryllium ions

We have measured prompt and delayed emission spectra of electrons from foilexcited Be, B^+, and Be^2+ ions at 300 keV. On the basis of recently calculated eigenvalues we identified two lines in the prompt Be^+ spectrum as transitions from 2s^22p and 2s2p^2. The delayed Be spectrum indicates that transitions from highly excited quintet states occur. We propose radiationless deexcitation with one excited spectator electron not involved in the transition.

Influence of the electronic shell structure on the elastic scattering of heavy ions

The interatomic potential of the system I - I at intermediate and small distances is calculated from atomic DFS electron densities within a statistical model. Structures in the potential, due to the electronic shells, are investigated. Calculations of the elastic differential scattering cross section for small angles and several keV impact energies show a detailed peak pattern which can be correlated to individual electronic shell interaction.

Study of 3d - 4f and 3d - 5f quartet and doublet transitions of doubly excited three-electron ions

We present the first observation of optical transitions between doubly excited doublet states in the term systems N V, 0 VI and F VII. The spectra were produced by foil excitation of fast ion beams. The assignment of the spectral lines was made by comparison with the results of MCDP calculations along the isoelectronic sequence. The same method also led to the identification of two 3d - 4f quartet transitions in Mg X.