Fakultät für Physik - Digitale Hochschulschriften der LMU - Teil 02/05

Im Rahmen dieser Arbeit wurde mit Fluoreszenz-Korrelationsspektroskopie (FCS) zum ersten Mal systematisch die Bindung von fluoreszenzmarkierten Peptiden an anionischen Lipidmembranen untersucht. Mit dieser Methode konnten Einzelmolekül-Messungen zur Bindung von myristoyliertem Alanin-reichen C Kinase Substrat, MARCKS (151-175), an unilamellare Vesikel mit einem Durchmesser von 100 nm durchgeführt werden. Die Vesikel bestanden aus dem neutralen Lipid Phosphatidylcholine (PC) und den negativ geladenen Lipiden Phosphatidylserine (PS) oder Phosphatidylinositol 4,5-bisphosphate (PIP2). Eine Signal/Rausch-Analyse ermöglichte die Bestimmung der Sensitivität und des linearen Messbereichs der Methode. Auf Grund der unterschiedlichen Korrelationszeiten der freien und gebundenen Peptide folgte aus den gemessenen Autokorrelationskurven der prozentuale Anteil des gebundenen Pepids. Die Bindung von MARCKS(151-175) an die anionischen Vesikel wurde für verschiedene prozentuale Anteile von PS und PIP2 gemessen. Sie war umso stärker, je höher der Anteil anionischer Lipide in der Membran und damit die attraktive elekrostatische Wechselwirkung war. Die ermittelten Bindungskonstanten stimmten gut mit den Resultaten überein, die mit etablierten konventionellen Techniken wie NMR, ITC oder Spinmarkierung gewonnen wurden. Die Experimente konnten zeigen, dass mit FCS direkte Messungen von nanomolaren Peptidkonzentrationen möglich sind. FCS stellt eine präzise Methode zur Untersuchung der Wechselwirkung von Peptiden und Proteinen mit Lipidmembranen dar.

Im zweiten Teil der Arbeit wurde die Selbstorganisation und das Aggregationsverhalten von verschiedenen synthetischen Gentransfer-Komplexen studiert. Mit der Methode der quantitativen Fluoreszenzmikroskopie wurde die Größenverteilung bestimmt und die Zahl der Plasmide pro Gentransfer-Komplex berechnet. Die Polyplexe stellen im Unterschied zu den Lipoplexen unter den experimentellen Bedingungen ein polydisperses kolloidales System dar. Unter dem Einfluss eines natürlichen Surfactants (Alveofact) war ein umgekehrtes Verhalten zu beobachten. Die Messungen zur Kinetik des kolloidalen Systems erfolgten mit der Fluoreszenz-Korrelationsspektroskopie. Mit dieser Methode wurde der Einfluss der Ionenkonzentration und von Alveofact auf die Aggregationskinetik von verschiedenen positiv geladenen Gentransfer-Komplexen untersucht. Die Experimente zeigten, dass die Geschwindigkeit der kolloidalen Aggregation mit der Ionenkonzentration drastisch zunimmt und die mittlere Zahl der Plasmide pro Komplex als Funktion der Zeit linear ansteigt. Nach der Inkubation mit Alveofact stellten die Polyplexe auch unter physiologischen Bedingungen ein stabiles kolloidales System dar und bestanden im Mittel aus 3-5 Plasmiden. Auch in diesem Fall wurde bei den DNA/Lipofectamine-Komplexen ein anderes Aggregationsverhalten beobachtet. Sie bildeten ohne die Einwirkung von Alveofact unabhängig von der Ionenkonzentration ein stabiles Kolloid und bestanden im Mittel aus nur zwei kondensierten Plasmiden. Dagegen führte die Inkubation mit Alveofact zu einer langsamen kolloidalen Aggregation. Die Lipoplexe erreichten in diesem Fall nach 60 min eine Größe von ~3-4 Plasmiden pro Komplex.

Mit Fluoreszenz-Korrelationsspektroskopie wurde das Transportverhalten verschiedener Vesikel und Gentransfer-Komplexe in einem negativ geladenen Polymer-Netzwerk (Mucin) untersucht. Die Größe und die Ladung der Partikel bestimmten die Diffusion durch das Polymer-Netzwerk. Kleinere Durchmesser und höhere negative Ladungen der Vesikel trugen zu einem effektiveren Transport durch das Netzwerk bei. Aus der Diffusionskonstante und der makroskopischen Viskosität der Polymerlösung wurden die Abweichungen von der Stokes-Einstein-Relation berechnet. Das Diffusionsverhalten anionischer Vesikel wurde zum Vergleich auch in einem positiv geladenen Kollagen-Netzwerk studiert. Bei den synthetischen Gentransfer-Komplexen mit positiver Überschussladung wurde auf Grund der Bindun

This dissertation presents a theoretical analysis of methods to

manipulate and control the momentum state of coherent

matter waves. Of particular interest is the coherent acceleration

of a quantum-degenerate atomic system, which, as a direct

consequence of the form of the de Broglie wavelength, results in

tunable source of matter waves. Such sources are of considerable

importance for a number of potential applications in the field of atom optics,

including the development of highly sensitive gyroscopes, accelerometers,

gravity gradiometers or atom lithography and holography, as well as for

potential uses in integrated atom optics.

Our basic setup consists of a Bose-Einstein condensate in a moving

optical lattice created by a pair of frequency-chirped

counterpropagating laser beams acting as a "conveyor belt'' for

ultracold atoms. Whereas the acceleration of ultracold

but non-condensed atoms in such a lattice was demonstrated earlier,

we extend this scheme to the case of Bose-Einstein condensates.

As a first step, we investigate the acceleration efficiency for various

acceleration rates and nonlinear interaction strengths. We find

parameter regimes where efficient acceleration is possible, i.e.

all atoms are accelerated to the same velocity and the initially sharp

momentum distribution and thus its monochromaticity is preserved.

However, in general we identify switch-on effects of the lattice, dynamical loss and nonlinear effects to be responsible for deterioration of the monochromaticity of the condensate: On the one hand, switch-on effects and dynamical loss induce a coupling of the initially populated momentum mode to other modes, thereby distributing the momentum over

several modes. On the other hand, the nonlinear release of mean field energy during the acceleration process causes the mode profile itself to broaden, also leading to a contamination of the initial monochromaticity.

As a second step, we discuss ways to improve this scheme by removing the

restriction of constant accelerations. We employ genetic algorithms to optimize the time-dependent motion of the lattice. We show that with such flexibility, it is possible to achieve a fast and highly efficient coherent acceleration of condensates, even when mean-field effects cannot be

neglected. The same scheme also enables the creation of arbitrary coherent superposition states in momentum space. The technique is thus suitable for building highly efficient momentum state beam splitters.

In addition to simply accelerating condensates, it is desirable

for many potential applications to transport atomic wave packets

without dispersion over large distances. This can be achieved by launching bright atomic solitons, where the effects of the nonlinearity counterbalance the dispersion. Placing a Bose-Einstein condensate with repulsive interactions in a lattice, one can create a negative effective mass. Under these circumstances bright and stable soliton solutions exist, so-called gap solitons. After a careful analysis of the soliton properties, we use the

tools we developed for condensate acceleration and demonstrate

two feasible schemes to excite the solitons.

Experimental data released after publication of our results demonstrating the acceleration of Bose-Einstein condensates in moving lattices and the very recent observation of atomic gap solitons indicates that our theoretical analysis was timely and indeed experimentally feasible.

As an outlook, we briefly comment on a new direction in the field

of atom optics that holds promise for future applications:

the use of quantum degenerate Fermi gases.

In atomic as well as in optical physics one often encounters situations

where there exists a coupling between several modes of a system.

Here, we illustrate the "toy model'' of a fermionic coupler where

transitions between two internal states are induced by Raman coupling.

Due to Fermi statistics and interatomic interactions, this is a simple example of a nonlinear m

Intra- and intermolecular charge transfer as well as internal conversion processes are studied in various molecular systems. The dynamics of these fundamental photoinduced processes are investigated by pump-probe femtosecond spectroscopy and steady-state fluorescence. Transient spectra are obtained using white light continuum as probe, while time resolved measurements are performed by probing at specific wavelengths with non dispersive detec-tion. Noncollinearly phase matched optical parametric amplifiers (NOPAs) are used as tun-able pump and probe pulse sources. This technique enables to study ultrafast phenomena with an unprecedented time resolution of 60 fs for UV-C excitation pulses at 270 nm.

Upon excitation of their structural subunits, triphenylmethane lactones (phenolphthalein and malachite green lactone) undergo ultrafast photoinduced electron transfer (ET) with the formation of a radical ion pair of their structural subunits. The phenol radical cation is formed by ET with a time constant of 50 fs and 80 fs after excitation to the S1 state of phe-nolphthalein in acetonitrile and ethyl acetate, respectively. In malachite green lactone both S2 → S1 electronic relaxation and ET are completed within 150 fs in aprotic (acetonitrile and ethyl acetate) as well as in protic environment (methanol). Subsequently, in methanol the opening of the lactone ring is detected directly by observing the appearance of the malachite green cation absorption band on a 2 - 4 ps time scale. The results demonstrate that the ET in these molecules occurs faster than the time scale of inertial solvation dynamics, while the lactone ring opening occurs on the time scale of longitudinal dielectric relaxation. It is as-sumed that on one side an intramolecular vibrational mode promotes the charge transfer and on the other side diffusive solvation dynamics is responsible for the breakage of the C-O bond in the lactone ring.

The controversial behavior of the excited biochromophore indole in water, which fluoresces on a nanosecond time scale and undergoes photoionization within 60 fs, is explained with an ultrafast branching occurring immediately after excitation. The excited indole population is divided by the ultrafast branching into a fraction (62%) which exhibits a 1La/1Lb state re-versal and a fraction (38%) that undergoes photoionization generating indole radicals and solvated electrons. The electron solvation dynamics is resolved to occur with a time constant of 350 fs. From the comparisons with the photoionization dynamics in neat water and in 1-methylindole the origin of the solvated electron has been found to be the intermolecular electron transfer to the solvent and not an H-transfer to the solvent.

Internal conversion (IC), an important nonradiative process occurring in organic com-pounds upon the UV radiation, is explored in o-hydroxybenzaldehyde (OHBA), a molecule that exhibits excited state intramolecular proton transfer (ESIPT). It is shown that the IC of OHBA proceeds as a thermally activated process over an energy barrier of about 200 meV caused by an avoided crossing between the ππ*- and πσ*-state. The IC shows pure statistical behavior depending on the total excitation photon energy although the preceding ESIPT is a balistic motion of a well-defined wavepacket. Thus, the coordinates involved in the ESIPT and in the IC are found to be orthogonal.

The X-ray properties of five Narrow-line Seyfert 1 galaxies (NLS1)

are analysed and presented

in this dissertation. The data were collected with XMM-Newton, and to date,

are of the highest quality ever obtained.

Themes which have evolved and appear fundamental in understanding NLS1 are:

near- or super-Eddington accretion by a "small" supermassive black hole,

partial covering, and reflection. Most of the objects presented in

this dissertation can adopt these principles.

The main results of this work are as follow.

Two observations of 1H0707-495 and one observation of IRAS 13224-3809 show sharp, spectral

drops above ~7 keV (Chapters 2 and 4).

The sharpness of the features, and absence of iron fluorescent emission and

K\beta UTA absorption,

challenge the possibility that the drops originate from

photonionisation. If partial covering from

a neutral absorber is adopted then outflows on the order of 0.05-0.15 c

are required. On the other hand, if the sharp drops are associated with the

blue wings of relativistically broadened Fe K\alpha lines

(Chapters 2 and 5) then the interpretation

requires light bending close to the black hole to explain the large

equivalent widths and variability properties.

Both interpretations require an iron overabundance

(3-10 times solar), suggesting that supersolar metallicities may

simply be characteristic of NLS1, probably due to strong starburst activity

close to the nucleus.

The general variability properties of NLS1 remain elusive, but

advances have been made. All of the Seyferts and quasars discussed here showed

rapid and extreme variability at some point during the observations.

IRAS 13224-3809 exhibited some of the most remarkable variability

(Chapter 3). Lags between the hard and soft energy bands

were detected, suggesting that fluctuations at low energies instigated

variability at higher energies. However, closer inspection revealed that the

lags alternate: sometimes the hard band follows, while at other times it leads.

Spectral variability was determined to be correlated with flux variations,

but more interestingly was the finding that the spectral variability also

lagged flux variations, resulting in flux-induced spectral variability.

For over 120 ks (spread over two observations), 1H0707-495 persistently displayed

flux variations by at least a factor of four.

During the first observation, when 1H0707-495 was in its lowest flux state ever

recorded,

there was no significant spectral variability.

The second

observation, when the source was in a higher flux state,

revealed strong spectral variability. Flux and spectral fluctuation

were never found to be significantly correlated (Chapter 4).

The quasar, PHL 1092, exhibited some of the most striking variability considering

its high luminosity (Chapter 7).

Indeed, an estimate of its radiative efficiency was in

excess of that expected from a Schwarzschild black hole. Interestingly,

the variability appeared to be entirely concentrated in the soft-excess, with

the power-law component appearing quiescent.

The closest example of class behaviour seen in the variability of

the group

was displayed by the two quasars I Zw 1 and NAB 0205+024

(Chapters 6 and 8, respectively).

Both objects exhibited a hard X-ray flare which was concentrated at energies higher than

~2 keV and accompanied by spectral variability.

A scenario in which the hard X-ray flare originates in the accretion disc

corona, and then irradiates the disc itself seem most applicable here.

I Zw 1 has been defined as the prototype NLS1 based on its optical properties.

In the X-rays it appears anything but prototypical.

Significant low-energy intrinsic absorption, a weak soft-excess, and

evidence for multiple iron emission lines suggest that other

processes are at work (Chapter 6).

PHL 1092 exhibited deviations from a power-law fit in the 2-10 keV band

(Chapter 7). The difference

could be interpreted as an emission line enhanced by light bending close

to a Kerr black hole.

The comp

The main purpose of the work presented in this thesis is to investigate the

phenomenon of resonant scattering of the Cosmic Microwave Background (CMB)

photons by atoms and molecules. The fine-structure transitions of the various

atoms and ions of Carbon, Nitrogen, Oxygen and other common metals have

wavelengths in the far-infrared regions, which are particularly suitable for

scattering the CMB photons at high redshifts ($2 \lesssim z \lesssim

30$). Since the CMB photons are released at redshifts $z\simeq 1100$, they must

interact with all the intervening matter before reaching us at $z=0$.

Therefore scattering of these photons in the far-IR

fine-structure lines of various

atoms and ions provide a plausible way to couple the radiation with the

matter at those redshifts and to study the enrichment and ionization

history of the universe. Moreover, rotational transitions of diatomic

molecules like the CO have wavelengths extending into the sub-millimeter

wavebands, and hence they can scatter the CMB photons at very low

redshifts. Studying the very low density gas of nearby galaxies

in CO lines can yield a

definitive signature of resonant scattering of the CMB photons through a

decrement in the background intensity of the microwave sky. Observation of

this scattering signal from any object in the sky will tell us about its

radial velocity in the CMB rest frame.

In this work we first derive the detailed formalism for the scattering

effect in presence of the peculiar motion of the scatterer. Then we

investigate the possibility to detect individual objects at different

redshifts through scattering and try to find applications for this

effect. Our main example is the possibility to find the peculiar motions of

nearby galaxies in the CMB rest frame through observation of

the scattering signal, which

we explore in detail. Next we discuss the density limits in

which scattering effect can dominate over

the line emission in individual objects. We

describe three types of critical densities, and show that detection of

single objects through scattering requires very low density,

whereas observation of the integrated scattering signal

coming from many unresolved objects in the sky will permit

us to probe higher densities. We discuss this effect subsequently,

as we compute the change in the angular fluctuations of the CMB sky

temperature through resonant scattering. We found that

the scattering signal gets strong enhancement

due to a non-zero correlation existing between the density perturbations at

the last scattering surface, where CMB anisotropies are

generated, and at the epoch of

scattering. This opens up a new way to study the ionization and enrichment

history of the universe, and we investigate various enrichment

scenarios and

the temperature fluctuations that might be caused by them. The resulting signal

is already within the sensitivity limits of some upcoming space- and

ground-based CMB experiments, and we show upto what extent they

shall be able to put

constraints on different enrichment histories. Finally we analyze the effect

of line and dust emission in the same frequency range that we used

for the detection of scattering signal. These emissions are coming from very

high density objects where active star formation is taking place, and due to

the compactness of their size as well as absence of any velocity

dependence the emission signal is significantly suppressed

at large angular scales, where scattering will be dominant. We present some

detailed analytic expressions for the scattering signal and also a method to

solve for the detailed statistical balance equations in a multi-level system

in the appendix.

Due to the singularities arising in quantum field theory

and the difficulties in quantizing gravity it is often believed that the description of spacetime by a smooth manifold should be given up at small length scales or high energies. In this work we will replace spacetime by noncommutative structures arising within the framework

of deformation quantization. The ordinary product between functions will be replaced by a *-product, an associative product for the space of functions on a manifold.

We develop a formalism to realize algebras defined by relations on function spaces. For this porpose we construct the Weyl-ordered *-product and present a method how to calculate *-products with the help of commuting vector fields.

Concepts developed in noncommutative differential geometry will be applied to this type of algebras and we construct actions for noncommutative field theories. In the classical limit these noncommutative theories become field theories on manifolds with nonvanishing curvature. It becomes clear that the application of *-products is very fruitful to the solution of noncommutative problems. In the semiclassical limit every *-product is related to a Poisson structure, every derivation of the algebra to a vector field on the manifold. Since in this limit many problems are reduced to a couple of differential equations the *-product representation makes it possible to construct noncommutative spaces corresponding to interesting Riemannian manifolds.

Derivations of *-products makes it further possible to extend noncommutative gauge theory in the Seiberg-Witten formalism with covariant derivatives. The resulting noncommutative gauge fields may be interpreted as one forms of a generalization of the exterior algebra of a manifold. For the Formality *-product we

prove the existence of the abelian Seiberg-Witten map for derivations of these *-products. We calculate the enveloping algebra valued non abelian Seiberg-Witten map pertubatively up to second order for the Weyl-ordered *-product. A general method to construct actions invariant under noncommutative gauge transformations is developed. In the commutative limit these theories are becoming gauge theories on curved backgrounds.

We study observables of noncommutative gauge theories and extend the concept of so called open Wilson lines to general noncommutative gauge theories. With help of this construction we give a formula for the inverse abelian Seiberg-Witten map on noncommutative spaces with nondegenerate *-products.

Die Absorptionsspektroskopie im mittleren infraroten (MIR, etwa 500-4000 cm-1) Spektralbereich ist ein wichtiges Hilfsmittel in der biomolekularen Forschung. Mit ihrer Hilfe können z.B. strukturelle Eigenschaften von Proteinen und enzymatisch katalysierte Reaktionen sichtbar gemacht werden. Zur Interpretation solcher Spektren benötigt man jedoch Rechenmethoden, vermittels derer MIR Spektren mit hoher Genauigkeit vorhergesagt werden können.

Im ersten Teil dieser Arbeit betrachte ich Cyclopyrimindimere (CPD), die durch ultraviolette Strahlung in dem Erbgutmolekül DNS entstehen und potentiell mutagene oder lethale Folgen für die Zelle haben. Um zukünftige Experimente zu leiten, welche die licht-induzierte Reparaturreaktion dieser Defekte durch das Enzym Photolyase mit zeitaufgelöster Spektroskopie verfolgen wollen, habe ich mit Hilfe der Dichtefunktionaltheorie (DFT) die MIR Spektren von Modellstrukturen einzelner Intermediate der CPD Reparatur berechnet. Die Ergebnisse zeigen, dass die Intermediate der CPD Reparatur anhand der spezifischen MIR Absorption ihrer Carbonylmoden identifiziert werden können und dass der Weg der Spaltung eines CPD in native DNS Basen auf diese Weise aufgeschlüsselt werden kann.

Im zweiten Teil dieser Arbeit untersuche ich jene Methoden, die in der Literatur zur Berechnung von MIR Spektren aus Molekulardyamik (MD) Simulationen, bei denen eine DFT Beschreibung eines Moleküls mit einer molekülmechanischen (MM) Beschreibung der Umgebung kombiniert wird, vorgeschlagen worden sind. Dazu leite ich die Vorschriften der verschiedenen Methoden für den Fall eines einzelnen Moleküls in einem polaren Lösungsmittel aus der linearen, quantenmechanischen Störungstheorie her. Anhand dieser Herleitung und der Ergebnisse einer exemplarischen Anwendung der Methoden auf eine DFT/MM-MD Simulation eines Formaldehydmoleküls in Wasser diskutiere ich die den jeweiligen Methoden zugrundeliegenden Annahmen und Näherungen sowie mögliche neue Verfahren zur Korrektur der durch die Näherungen induzierten Fehler bei der Berechnung von MIR Spektren.

Ferner entwickle ich aus dieser Analyse ein neues Verfahren zur Berechnung von MIR Spektren kleiner Moleküle in polaren Lösungsmitteln, mit dessen Hilfe sich die Frequenzfluktuationen des gelösten Moleküls, die durch die Wechselwirkung mit der fluktuierenden Lösungsmittelumgebung entstehen, mit einer Auflösung von etwa 10-30 fs berechnen lassen. Anhand einer exemplarischen Anwendung zeige ich, dass es diese Methode erlaubt, die Ursachen der Frequenzfluktuationen im Detail zu untersuchen und deren Beiträge zu MIR Linienbreiten zu ermitteln.

Zusammenfassung O ene Sternhaufen stellen als Gruppen von Sternen gleichen Alters und aufgrund ihres Ursprungs gleicher chemischer Zusammensetzung ein einzigartiges Labor zum Test von Sternentwicklungsmodellen dar. Diese Arbeit beschaftigt sich dabei mit dem o enen Sternhaufen Melotte 111 und den Pleiaden. Um Beobachtung und Modell vergleichen zu konnen, ist es dabei notwendig die stellaren Parameter E ektivtemperatur, Gravitationsbeschleunigung, Metallizitat und Mikroturbulenz mit gro tmoglicher Prazision fur Sterne im gesamten in o enen Haufen vorkommenden Parameterbereich zu messen. Um diesem Anspruch gerecht zu werden wird im Rahmen dieser Arbeit das Opacity Sampling Modellatmospharenprogramm MAFAGS-OS eingefuhrt. Auf einer Datenbasis von mehr als 20 Millionen gebunden-gebunden Ubergangen von Elementen der Ionisationsstufen I, II und III sowie 11 diatomischen Molekulen basierend werden Methoden der Linienauswahl, sowie ein geeignetes Stutzstellengitter fur Sterne der Spektraltypen A, F und G fur Entwicklungsstadien von der Hauptreihe bis zum Turno und Sterne verschiedener Metallizitat untersucht und festgelegt. MAFAGS-OS erweist sich im Vergleich mit der solaren Flussverteilung und den " Farben der Sonne\als herkommlichen Opacity Distribution Function (ODF) Modellen uberlegen. Das sogenannte Problem der missing ultraviolet opacity verschwindet in der Sonne dabei fast zur Ganze.1 Bezuglich der Sonne bleiben allerdings die von herkommlichen Modellen bekannten De zite in d

Ziel der Arbeit ist die Untersuchung von Magnetfeldern im

intergalaktischen Gas von Galaxienhaufen mittels Faradayrotationskarten extragalaktischer Radioquellen, die in oder hinter einem Galaxienhaufen lokalisiert sind. Faradayrotation entsteht, wenn linear polarisierte Strahlung einer solchen Quelle durch ein magnetisiertes Medium propagiert und dabei dessen Polarisationsebene rotiert wird. Multifrequenzbeobachtungen erlauben die Konstruktion von Faradayrotationskarten. Die statistische Charakterisierung und Analyse dieser Karten erlaubt es, Eigenschaften der Magnetfelder, welche mit dem Plasma in Galaxienhaufen in

Verbindung stehen, zu bestimmen. Es wurde untersucht, ob es einen Beweis dafuer gibt, dass die Faradayrotation im quellennahen Material erzeugt wird oder im magnetisierten Plasma der Galaxienhaufen. Dazu wurden zwei statistische Masse zur Charakterisierung der Daten eingefuehrt. Beide Masse sind ausserdem wertvolle Indikatoren fuer moegliche Probleme bei der Berechnung von Magetfeldeigenschaften auf der Basis von Faradayrotationsmessungen. Die Masse wurden auf Faradayrotationsmessungen von ausgedehnten Radioquellen angewandt. Es konnten keine Hinweise auf quellennahe Enstehungsorte der Faradyrotation gefunden werden. Aufgrund von davon unabhaengigen Beweisen, wurde festgestellt, dass die Magnetfelder, welche die Faradayrotation verursachen, mit dem Plasma in Galaxienhaufen in Zusammenhang stehen sollten.Eine statistische Analyse von Faradayrotationsmessungen mittels Autokorrelationsfunktionen und aequivalent dazu Energiespektren wurde entwickelt um Magnetfeldstaerken und -korrelationslaengen zu bestimmen. Diese Analyse stuetzt sich auf die Annahme, dass die Magnetfelder statistisch isotrop im Faradayrotationsgebiet verteilt sind. Sie benutzt eine sogenannte Fensterfunktion, die das Probenvolumen beschreibt, in welchem Magnetfelder detektierbar sind. Die Faradayrotationskarten von drei ausgedehnten Radioquellen (d.h. 3C75 in Abell 400, 3C465 in 2634 und Hydra A in Abell 780) wurden mittels dieser Methode neu ausgewertet und dabei Magnetfeldstaerken von 1 bis 10 muGauss fuer diese drei Galaxienhaufen abgeleitet.Die Messung von magnetischen Energiespektren erfordert Faradayrotationskarten hoechster Guete. Um Artefakte durch die Datenreduktion zu vermeiden, wurde ein neuer Algorithmus -- Pacman -- zur Berechnung von Faradayrotationskarten

entwickelt. Verschiedene statistische Tests zeigen, dass dieser Algorithmus stabil ist und zuverlaessige Faradayrotationswerte berechnet. Zur genauen Messung von magnetischen Energiespektren aus den Pacman Karten wurde ein Maximum-Likelihood-Schaetzer, der auf der zuvor eingefuehrten Theorie beruht. Diese neue Methode erlaubt erstmals, die statistische Unsicherheit des Ergebnisses anzugeben. Des weiteren beruecksichtigt diese Methode das begrenzte Probenvolumen und macht die verlaessliche Bestimmung von Energiespektren moeglich. Diese Maximum-likelihood Methode wurde auf Pacman Faradayrotationskarten von Hydra A angewandt. Beruecksichtigt man die Ungewissheit ueber die exakte

Probengeometrie des Faradaygebietes, erhaelt man eine

Magnetfeldstaerke von 7 +/- 2 muGauss. Das berechnete Energiespektrum folgt einem Kolmogorov aehnlichem Energiespektrum ueber wenigstens eine Groesseenordnung. Die magnetische Energie ist auf einer dominanten Skale von ungefaehr 3 kpc konzentriert.

Nanoelectromechanics is a growing field. Nevertheless, the static deflections of nanoelectromechanical systems are hardly investigated. Since these are required for most nanomechanical tools, e. g. nanotweezers, they are dealt with in the work presented. A new fabrication scheme to build fully freely suspended structures out of silicon-on-insulator wafers was developed to get nanostructures with a hole-aperture right beneath them. The expected deflections of the fabricated double cantilever system were calculated using elasticity theory. To measure the quasistatic deflections of these nanosystems under a bias voltage, a scanning confocal optical microscope was used in conjunction with demodulation of the reflected signal. This worked for freely suspended as well as fully freely suspended structures and the system was operated under ambient conditions. Using this technique, signals at the first, second, and third harmonic of the excitation frequency could be detected. These were correlated to the deflection in horizontal and vertical direction. The vertical deflection is a parasitic one due to the vicinity of the substrate, since the system was designed to show a horizontal deflection, only. The fully freely suspended structures, in contrast, do not show deflections resulting from forces towards the substrate. To distinguish between the two directions of motion as well as to get a better understanding of the interference-dominated scanning images of the structures having a substrate beneath, numerical simulations of the imaging were performed. These reproduce the images as well as the demodulated signals quite well. The sensitivity of the optical demodulation measurement was shown to be 6 pm /Sqrt(Hz) (rms), a deflection of about 2 angstrom could be proven. Using the same set-up in a non-scanning way, resonances of the deflected structures were identified. The fabrication as well as detection schemes are fundamental for the development of nanotweezers capable of repositioning nano-scaled objects. Additionally, some calculations concerning the melting that occurred to the contacted nanostructures under investigation by a scanning electron microscope are presented. The electroluminescence that one of the silicon nanostructures accidentally showed is interpreted in terms of the analogy to spark-processed silicon. In conclusion, scanning confocal optical microscopy is shown to be a highly sensitive as well as non-destructive technique to investigate quasistatic deflections of nanoelectromechanical systems in the angstrom range.