The control of chemical reactions is of great interest from both a fundamental and an industrial perspective. Among the many different ways to control the outcome of chemical reactions, control with the electric field waveform of laser pulses offers the possibility to control dynamics on the femtosecond, or even attosecond, timescale. This thesis presents work on a recently developed approach to control molecular processes by guiding electron motion inside molecules with the waveform of light. The work presented in this thesis started right after the pioneering experiment on laser-induced electron localization in the dissociative ionization of molecular hydrogen with phase-stabilized few-cycle laser pulses. First, electron localization was studied for the different isotopomers H_2, HD, and D_2. The laser waveform driven strongly coupled electron and nuclear dynamics was investigated with single and two-color control schemes using near-infrared pulses as the fundamental. Furthermore, the subcycle control of charge-directed reactivity in D_2 at mid-infrared wavelengths (2.1 micrometers) was both observed experimentally and investigated quantum-dynamically. Two reaction pathways could be detected and controlled simultaneously for the first time. Extending the approach from the prototype hydrogen molecules, which contain only a single remaining electron after initial ionization, towards complex multielectron systems was a major goal of this thesis and first achieved for carbon monoxide. Experimental and theoretical results (by our collaborators from the de Vivie-Riedle group) on the waveform control of the directional emission of C^+ and O^+ fragments from the dissociative ionization of CO shed light on the complex mechanisms responsible for the waveform control in multielectron systems. In particular, it was found that not only the dissociation dynamics but also the ionization can lead to an observable asymmetry in the directional ion emission. In CO the contributions from these two processes could not be experimentally distinguished. Studies on another heteronuclear target, DCl, showed that for this molecule mainly the ionization step is responsible for an asymmetry in the fragment emission that can be controlled with the laser waveform. Another result of the studies on complex molecules was that the angular distributions of emitted ions from the breakup of the molecules in few-cycle laser fields showed the contributions of various orbitals in the ionization step. These results were supported by a new theoretical treatment by our collaborators from the de Vivie-Riedle group based on electronic structure theory for diatomic and larger systems, where multi-orbital contributions could be taken into account. Studies of the angle-dependent ionization of both homonuclear N_2, O_2 and heteronuclear CO and DCl molecules in few-cycle laser fields clearly show the importance of multi-orbital contributions (two HOMOs or HOMO+HOMO-1). Finally, waveform-controlled laser fields have been applied to orient molecules. Our findings on DCl suggested that samples of oriented molecular ions can be generated under field-free conditions, where the angle-dependent preferential ionization with a near single-cycle pulse is responsible for the orientation. The control of rotational wave packet dynamics by two-color laser fields was observed for CO and can be interpreted in the framework of two mechanisms: A) the hyperpolarizability orientation mechanism that dominates at low intensities, where the ionization probability is quite low and B) the ionization depletion mechanisms that prevails at high intensities, where substantial ionization occurs.

Durch moderne Laserspektroskopie ist es mittlerweile möglich, chemische Reaktionen mit einer Zeitauflösung von wenigen Femtosekunden zu untersuchen. Auf der anderen Seite kann die Molekülstruktur mithilfe von Röntgenstrukturanalyse sehr exakt bestimmt werden. Die vorliegende Doktorarbeit beschäftigt sich damit, diese beiden Gebiete zusammenzubringen. Der erste Teil der Dissertation beschreibt den Aufbau einer Laserplasmaquelle am Lehrstuhl für BioMolekulare Optik. Ein hochenergetischer Laserimpuls wird in einer Vakuumkammer auf ein Kupferband fokussiert. Dabei entsteht charakteristische Kupfer-K-alpha-Strahlung, die auf die kristalline Probe abgebildet wird. Ein zweiter Laserimpuls induziert in der Probe eine chemische Reaktion, die die Kristallstruktur ändert. Mit diesem Aufbau sind Röntgenbeugungsmessungen mit einer Zeitauflösung von wenigen hundert Femtosekunden möglich. An einem möglichen Probenkristall, DIABN, wurden zudem Transmissionsmessungen mit einer Röntgen-Streak-Kamera durchgeführt. Dieses Molekül zeigt einen Ladungstransferzustand auch in der kristallinen Phase, welcher mit einer Strukturänderung einhergeht. Der Ladungstransfer beeinflusst aber auch die Ausrichtung der umgebenden Moleküle, was die Extinktion des Kristalls stark verändert. Dieser Effekt kann mit zeitaufgelösten Transmissionsmessungen untersucht werden, bevor Röntgenbeugungsexperimente durchgeführt werden. Der Hauptteil der Dissertation handelt von der Excimerbildung in 9,10-Dichloroanthrazen (DCA). Mit zeitaufgelöster Emissions- und Absorptionsspektroskopie wurde zunächst das Verhalten in Lösung beobachtet. Hier konnte erstmals eine detaillierte Studie zur Konzentrationsabhängigkeit der Excimerbildung von DCA erstellt werden. Mit den dabei gewonnen Erkenntnissen konnte eine vergleichende Untersuchung der beiden Kristallformen, alpha und beta, durchgeführt werden. Entgegen andersartigen Darstellungen in der Literatur konnte gezeigt werden, dass in der alpha-Form keine Excimerbildung stattfindet, während für die beta-Form die Bildungsrate bei Raumtemperatur bestimmt werden konnte. Die experimentellen Befunde lassen sich wie folgt erklären: Während in Lösung die Bildungsrate mit der Konzentration steigt, da es ein diffusionskontrollierter Prozess ist, sind im Kristall die beteiligten Moleküle relativ starr im Kristallgitter fixiert. In der beta-Form verhindert die relative Anordnung der Moleküle eine Excimerbildung, wohingegen in der alpha-Form die Moleküle fast perfekt parallel ausgerichtet sind und innerhalb kürzester Zeit ein Excimer bilden. Dieses System ist eine ideale Probe für die neu aufgebaute Laserplasmaquelle.

Idealized numerical model experiments are presented to investigate the convective generation of vertical vorticity in a tropical depression. The calculations are motivated by observations made during the recent PREDICT field experiment to study tropical cyclogenesis, and by a desire to understand the aggregation of vorticity debris produced by deep convection in models of tropical cyclogenesis to form a monopole vortex. One aim is to isolate and quantify the effects of low to mid level dry air on convective cells that form within a depression and, in particular, on the generation of vertical vorticity in these cells. Another aim is to isolate the effects of a unidirectional boundary layer wind profile on storm structure, especially on vertical vorticity production and updraught splitting, and the combined effects of horizontal and vertical shear on vertical vorticity production, with and without background rotation. A third aim is to isolate the effects of a vortex boundary-layer wind profile on tropical deep convection, focussing especially on the morphology of vertical vorticity that develops. The growing convective updraughts, that are initiated by a near surface thermal perturbation, amplify locally the ambient rotation at low levels by more than an order of magnitude and this vorticity persists long after the updraught has decayed, supporting the results of an earlier study. The results of calculations with dry air aloft do not support a common perception that the dry air produces stronger downdraughts. In calculations where the vertical wind shear changes sign at some level near the top of the boundary layer, as occurs in warm-cored disturbances such as tropical depressions or tropical cyclones, it was found that the tilting of horizontal vorticity by a convective updraught leads not only to dipole patterns of vertical vorticity, but also to a reversal in sign of the updraught rotation with height. This feature is quite unlike the structure in a typical middle-latitude `supercell' storm. These results provide an essential first step to understanding the interaction between deep convective elements in a tropical depression or tropical cyclone. An increase in the magnitude of boundary-layer shear was found to have the dual effect of weakening the development of the initial thermal, which is detrimental to vertical vorticity production by stretching and tilting, while at the same time increasing the magnitude of horizontal vorticity that can be tilted. The results provide a basis for appraising a recent conjecture concerning the role of storm splitting in explaining the contraction of the eyewall in tropical cyclones.

No description available.

Concentrating solar technologies compete with other rapidly developing renewable energy sources. To succeed it is vital to lower the levelized cost of energy. There are several parameters that can be optimized to reach this goal, but a key component is the improvement of the resource assessment. A better prediction of the solar resource for new facilities brings down financing costs as financial risks are reduced. Moreover, improved solar resource assessment allows to optimize new facilities in regard to the local insolation conditions. This increases energy and cost efficiency. One parameter that is becoming more and more important for the resource assessment is the circumsolar radiation. It is caused by forward scattering of sun light by cloud or aerosol particles. However, measuring circumsolar radiation is demanding and only very limited data sets are available. As a step to bridge this gap, a method was developed in this study to determine circumsolar radiation from readily available data on clouds and aerosol. Specifically, the effective radius and optical thickness of cirrus clouds were used, as well as area mass loadings of several aerosol components. The core of the method to determine the circumsolar radiation is a fast yet precise parameterization. It allows to compute the circumsolar radiation by simple analytical expressions from previously tabulated coefficients, instead of solving the radiative transfer by time-consuming numerical simulations. The lookup tables were generated by extensive calculations using a specifically adjusted version of the Monte Carlo radiative transfer model MYSTIC. To this end, MYSTIC was enhanced with a realistic radiation source: The point source used so far was replaced by a extended sun disk which features a wavelength dependent brightness distribution. The evaluated aerosol area mass loadings were obtained from the European Centre for Medium-Range Weather Forecasts (ECMWF) as model output of the Integrated Forecast System (IFS). To derive the cirrus cloud properties the APICS retrieval framework was applied to Meteosat Second Generation (MSG) measurements. During the course of this study APICS was optimized regarding the retrieval of optically thin cirrus clouds. To this end, a new ground albedo data set was generated on the basis of MSG measurements which serves as a priori assumption in the retrieval. This new data set is, in contrast the so far used one, consistent to the other assumptions made within the retrieval. This is an important pre-requisite for the successful retrieval of optically thin cirrus clouds. Furthermore, APICS was operated with a new cloud mask based on output of the COCS cirrus cloud property retrieval algorithm. It replaces the formerly used cloud mask from the MeCiDa cirrus detection algorithm. Thereby in the order of 70 to 80 percent more optically thin cirrus clouds can be considered, which allow enough light to pass for operation of a typical solar thermal utility. Considering cirrus clouds the prevailing ice particle shape is an uncertainty factor in the cloud property retrieval as well as in the computation of circumsolar radiation. So far it cannot be determined from MSG but must be assumed a priori. To allow for an uncertainty analysis concerning this parameter APICS was extended to consider several new ice particle shapes in the retrieval process. It was found, the nescience of the ice particle shape leads to an uncertainty of up to 50% in the mean circumsolar irradiance. The newly developed method for the retrieval of circumsolar radiation was validated with ground measurements of the circumsolar ratio (CSR) performed at the Plataforma Solar de Almería (PSA). This showed that the statistical distribution of the circumsolar radiation can be well characterized with both of the two employed ``Baum'' ice particle shape parameterizations. When comparing instantaneous values timing and amplitude errors become evident, tough. For the circumsolar ratio (CSR) the validation yielded a mean absolute deviation (MAD) of 0.11 for both ``Baum'' parameterizations, a bias of 4% and -11%, respectively, and a Spearman rank correlation r_rank of 0.54 and 0.48, respectively. If measurements with sub-scale cumulus clouds within the relevant satellite pixels were manually removed, the agreement of instantaneous values improved. This reflects in the MAD values of 0.08 and 0.07, respectively, and r_rank values to 0.79 and 0.76, respectively. Furthermore, it was found that for aerosol the CSR is strongly underestimated if the IFS output is used head on. Only after adjusting the aerosol mass loadings reasonable values can be obtained. An underrepresentation of large dust particles in the IFS seems most likely to be reason for this. In the future the method developed in this study can be extended and combined with other data sources. While ground-based reference measurements so far only allowed the assessment of the circumsolar radiation at few specific measurement sites, the newly developed method makes it possible to survey arbitrary sites. / Konzentrierende Solarkraft steht im Wettstreit mit anderen sich dynamisch entwickelnden erneuerbaren Energiequellen. Ein zentraler Erfolgsfaktor ist dabei die Verringerung der Energieerzeugungskosten. Bei der Verfolgung dieses Ziels kommt der verbesserten Bestimmung der Einstrahlung eine wichtige Rolle zu. Finanzierungskosten für Neuanlagen können durch eine genauere Vorhersage der solaren Resource verringert werden, weil diese zu einer Reduzierung der finanziellen Risiken führt. Desweiteren erlaubt eine verbesserte Bestimmung der Einstrahlung zukünftige Anlagen in Bezug auf die lokalen Bedingungen zu optimieren. Dies senkt die Kosten und erhöht die Energieeffizienz. Die Zirkumsolarstrahlung ist ein Parameter, dem bei der Resourcenbestimmung immer mehr Aufmerksamkeit zu Teil wird. Sie wird durch Vorwärtsstreuung des Sonnenlichts an Wolken- und Aerosolpartikeln hervorgerufen. Die Messung von Zirkumsolarstrahlung ist jedoch anspruchsvoll und es existieren nur wenige Messreihen von eingeschränktem Umfang. Um die Lücke zwischen der vermehrten Nachfrage nach Daten zur Zirkumsolarstrahlung und deren eingeschränkter Verfügbarkeit zu füllen, wurde in dieser Arbeit eine Methode zur Bestimmung der Zirkumsolarstrahlung aus verfügbaren Datensätzen von Aerosol- und Wolkeneigenschaften entwickelt. Im Speziellen wurden die optische Dicke und der Effektivradius von Cirrus-Wolken, sowie die Flächenmassenkonzentration verschiedener Aerosolkomponenten ausgewertet. Den Kern der Methode zur Ableitung der Zirkumsolarstrahlung stellt eine schnelle und dennoch genaue Parametrisierung dar. Diese erlaubt es die Zirkumsolarstrahlung mittels einfacher analytischer Ausdrücke aus zuvor tabellierten Koeffizienten zu berechnen, anstatt den Strahlungstransport zeitaufwändig numerisch zu berechnen. Die entsprechenden Tabellen wurden mittels umfangreicher Simulationen mit einer speziell angepassten Version des Monte Carlo Strahlungstransportmodells MYSTIC erstellt. MYSTIC wurde im Rahmen der Studie unter anderem um eine realistische Strahlungsquelle erweitert, indem die bisher verwendete Punktquelle durch eine ausgedehnte Sonnenscheibe mit wellenlängenabhängiger Helligkeitsverteilung ersetzt wurde. Die ausgewerteten Aerosolflächenmassenkonzentrationen wurden als Modellausgabe des Integrated Forecast System (IFS) vom European Centre for Medium-Range Weather Forecasts (ECMWF) bezogen. Um die Wolkeneigenschaften von Cirren abzuleiten wurde das APICS Retrievalsystem auf Messungen der Meteosat Second Generation (MSG) Satelliten angewandt. Im Zuge der Studie wurde APICS für das Retrieval optisch dünner Cirren optimiert. Dazu wurde ein neuer Datensatz der Bodenalbedo auf Basis von MSG Messungen generiert, der als a priori Annahme in das Retrieval einfließt. Dieser neue Datensatz ist, im Gegensatz zu dem bisher verwendeten, konsistent zu den anderen innerhalb des Retrievals getroffenen Annahmen. Dies ist eine wichtige Voraussetzung für die Ableitung der Eigenschaften von optisch dünnen Cirren. Desweiteren wurde APICS mit einer neuen Wolkenmaske betrieben, die auf der Ausgabe des COCS-Cirrenretrievals basiert. Sie ersetzt die zuvor genutzte Wolkenmaske des MeCiDa Eiswolkendetektionsalgorithmus. Dadurch können etwa 70 bis 80 Prozent mehr von jenen dünnen Cirren berücksichtigt werden, die noch genug Sonnenlicht zum Betrieb einer typischen solar-thermischen Anlage passieren lassen. In Bezug auf Cirren stellt die Form der Eispartikel einen Unsicherheitsfaktor dar - sowohl bei der Ableitung der Wolkeneigenschaften, als auch bei der Berechnung der Zirkumsolarstrahlung. Bisher gibt es noch keine Möglichkeit die Partikelform von MSG aus zu bestimmen, sondern es muss eine Annahme a priori gemacht werden. Um eine Bestimmung der daraus folgenden Unsicherheit zu ermöglichen wurde APICS erweitert, so dass mehrere neue Eispartikelformen bei der Ableitung der Wolkeneigenschaften verwendet werden können. Damit konnte eine Unsicherheit in der Größenordnung von bis zu 50% in der mittleren Zirkumsolarstrahlung festgestellt werden, die aus der Unbestimmtheit der Eispartikelform folgt. Die entwickelte Methode zur Ableitung der Zirkumsolarstrahlung wurde mit Bodenmessungen des Zirkumsolarverhältnis (engl. circumsolar ratio, CSR) validiert, die an der Plataforma Solar de Almería (PSA) durchgeführt wurden. Dabei zeigte sich, dass die statistische Verteilung der Zirkumsolarstrahlung mit beiden der verwendeten „Baum“ Eispartikelformmischungen gut charakterisiert werden kann. Beim Vergleich instantaner Werte treten jedoch Timing- und Amplitudenfehlern auf. In der Validierung zeigte sich für das CSR eine mittlere absolute Abweichung (engl. mean absolute deviation, MAD) von 0.11 für beide „Baum“ Parametrisierungen, ein Bias von 4% bzw. -11% und eine Spearman Rang-Korrelation r_rank von 0.54 bzw. 0.48. Wenn Messungen mit sub-skaligen Cumulus Wolken innerhalb der entsprechenden Satellitenpixel manuell ausgefiltert wurden, verbesserte sich die Übereinstimmung instantaner Werte. Dies spiegelt sich wider in MAD-Werten von 0.08 bzw. 0.07 und r_rank-Werten von 0.79 bzw. 0.76. Des Weiteren stellte sich heraus, dass das von Aerosol verursachte CSR deutlich unterschätzt wird, wenn die Daten vom IFS unmodifiziert verwendet werden. Erst nach einer Anpassung der Aerosolflächenmassenkonzentration können sinnvolle Ergebnisse erzielt werden. Vermutlich ist eine zu geringe Konzentration von großen Mineralstaubpartikeln im IFS der Grund für die Unterschätzung der CSR. Die entwickelte Methode kann in Zukunft ausgeweitet und mit anderen Datenquellen kombiniert werden. Während bodengebundene Referenzmessungen bisher die Beurteilung der Zirkumsolarstrahlung an nur wenigen Messstationen zulassen, können mit der hier neu entwickelten Methode beliebige Kraftwerksstandorte begutachtet werden.

Plasmonics with heavily doped semiconductor nanocrystals (NCs) is an emerging field in NC science. However, impurity doping of NCs remains far from trivial and is, as yet, dominated by a low chemical control over the incorporated dopant atoms. An appealing alternative is vacancy doping, where the formation of vacancies in the structure is responsible for an increased carrier density and elegantly circumvents the issues related to impurity doping. Due to high carrier densities of around 10^21cm^(-3) localized surface plasmon resonances (LSPRs) in the near infrared (NIR) are expected, and as such highlighted to close the gap between conventionally doped NCs and noble metal nanoparticles. Copper chalcogenide NCs, namely copper sulfide (Cu2-xS), copper selenide (Cu2-xSe), and copper telluride (Cu2-xTe), are an attractive example of vacancy doped semiconductor NCs, with spectra dominated by intense NIR resonances. Within this study thorough experimental evidence has been given to prove the plasmonic nature of those NIR resonances. By presenting typical plasmonic characteristics, such as refractive index sensitivity of the LSPR, its intrinsic size dependence, plasmon dynamics, or interparticle plasmon coupling, the LSPRs in copper chalcogenide NCs have unambiguously been identified. The chemical nature of vacancy doping turns out to deliver an additional, highly attractive means of control over the LSPR in vacancy doped copper chalcogenide NCs. Through chemical tailoring of the copper vacancy density via controlled oxidation and reduction, as shown in this study, a reversible tuning of the LSPR over a wide range of frequencies in the NIR (1000-2000 nm) becomes feasible. This highlights copper chalcogenide NCs over conventional plasmonic materials. Notably, the complete suppression of the LSPR uncovers the excitonic features present only in the purely semiconducting, un-doped NCs and reveals the unique option to selectively address excitons and highly tunable LSPRs in one material (bandgap Eg~1.2 eV). As such, copper chalcogenide NCs appear to hold as an attractive material system for the investigation of exciton plasmon interactions. Indeed, a quenching of the excitonic transitions in the presence of the developing LSPR is demonstrated within this work, with a full recovery of the initial excitonic properties upon its suppression. A theoretical study on the shape dependent plasmonic properties of Cu2-xTe NCs reveals a deviation from the usual Drude model and suggests that the carriers in vacancy doped copper chalcogenide NCs cannot be treated as fully free. On the other hand, the Lorentz model of localized oscillators appears to account for the weak shape dependence, as observed experimentally, indicating an essential degree of localization of the carriers in vacancy doped copper chalcogenide NCs. Taken together, this work delivers a huge step toward the complete optical and structural characterization of plasmonic copper chalcogenide NCs. The advantages of semiconductor NC chemistry have been exploited to provide access to novel plasmonic shapes, such as tetrapods that have not been feasible to produce so far. A precise size, shape and phase control presents the basis for this study, and together with a thorough theoretical investigation delivers important aspects to uncover the tunable plasmonic properties of vacancy doped copper chalcogenide NCs.

One of the most fundamental correlations between the properties of galaxies in the local Universe is the so-called morphology-density relation (Dressler 1980). A plethora of studies utilizing multi-wavelength tracers of activity have shown that late type star forming galaxies favour low density regions in the local Universe (e.g. G´omez et al. 2003). In particular, the cores of massive galaxy clusters are galaxy graveyards full of massive spheroids that are dominated by old stellar populations. A variety of physical processes might be effective in suppressing star formation and affecting the morphology of cluster and group galaxies. Broadly speaking, these can be grouped in two big families: (i) interactions with other cluster members and/or with the cluster gravitational potential and (ii) interactions with the hot gas that permeates massive galaxy systems. Galaxy groups are the most common galaxy environment in our Universe, bridging the gap between the low density field and the crowded galaxy clusters. Indeed, as many as 50%-70% of galaxies reside in galaxy groups in the nearby Universe (Huchra & Geller 1982; Eke et al. 2004), while only a few percent are contained in the denser cluster cores. In addition, in the current bottom-up paradigm of structure formation, galaxy groups are the building blocks of more massive systems: they merge to form clusters. As structures grow, galaxies join more and more massive systems, spending most of their life in galaxy groups before entering the cluster environment. Thus, it is plausible to ask if group-related processes may drive the observed relations between galaxy properties and their environment. To shed light on this topic we have built the largest X-ray selected samples of galaxy groups with secure spectroscopic identification on the major blank field surveys. For this purpose, we combine deep X-ray Chandra and XMM data of the four major blank fields (All-wavelength Extended Groth Strip International Survey (AEGIS), the COSMOS field, the Extended Chandra Deep Field South (ECDFS), and the Chandra Deep Field North (CDFN) ). The group catalog in each field is created by associating any X-ray extended emission to a galaxy overdensity in the 3D space. This is feasible given the extremely rich spectroscopic coverage of these fields. Our identification method and the dynamical analysis used to identify the galaxy group members and to estimate the group velocity dispersion is extensively tested on the AEGIS field and with mock catalogs extracted from the Millennium Simulation (Springel et al. 2005). The effect of dynamical complexity, substructure, shape of X-ray emission, different radial and redshift cuts have been explored on the LX −sigma relation. We also discover a high redshift group at z~1.54 in the AEGIS field. This detection illustrates that mega-second Chandra exposures are required for detecting such objects in the volume of deep fields. We provide an accurate measure of the Star Formation Rate (SFR) of galaxies by using the deepest available Herschel PACS and Spitzer MIPS data available for the considered fields. We also provide a well-calibrated estimate of the SFR derived by using the SED fitting technique for undetected sources in mid- and far-infrared observations. Using this unique sample, we conduct a comprehensive analysis of the dependence of the total SFR , total stellar masses and halo occupation distribution (HOD) of massive galaxies (M*>10^10 M_sun) on the halo mass of the groups with rigorous consideration of uncertainties. We observe a clear evolution in the level of star formation (SF) activity in galaxy groups. Indeed, the total star formation activity in high redshift (0.5<z<1.1) groups is higher with respect to the low redshift (0.15<z<0.5) sample at any mass by almost 0.8 ± 0.1 dex. A milder difference (0.35 ± 0.1 dex) is observed between the [0.15-0.5] redshift bin and the groups at z < 0.085. This evolution seems to be much faster than the one observed in the whole galaxy population dominated by lower mass halos. This would imply that the level of SF activity is declining more rapidly since z~1.1 in the more massive halos than in the more common lower mass halos, confirming a “halo downsizing” effect as discussed already in Popesso et al. (2012). The HOD and the total stellar mass-M200 relation are consistent with a linear relation in any redshift bin in the M_200 range considered in our analysis. We do not observe any evolution in the HOD since z~1.1. Similarly we do not observe evolution in the relation between the total stellar mass of the groups and the total mass, in agreement with the results of Giodini et al (2012). The picture emerging from our findings is that massive groups at M_200~10^13−14 M_sun have already accreted the same amount of mass and have the same number of galaxies as the low redshift counterpart, as predicted by Stewart et al. (2008). This implies that the most evident evolution of the galaxy population of the most massive systems acts in terms of quenching their galaxy star formation activity. The analysis of the evolution of the fraction of SF galaxies as a function of halo mass or velocity dispersion show that high mass systems seem to be already evolved at z~1 by showing a fraction of star forming galaxies consistent with the low redshift counterpart at z < 0.085. Given the almost linear relation between the total SFR and M_200 in the high-z sample, this implies that most of the contribution to the total SFR of the most massive systems (M_200~ 10^14 M_sun) is given by few highly star forming galaxies, while in lower mass systems (M_200~10^13 M_sun) is given by many galaxies of average activity. This would be an additional sign of a faster evolution in the more massive systems in terms of star formation activity with respect to lower mass groups. Thus, it would confirm the “halo downsizing” effect. The comparison of our results with the prediction of the Millennium Simulation semi-analytical model confirms the known problem of the models. We confirm the strong bias due to the “satellite overquenching” problem in suppressing significantly the SF activity of group galaxies (more than an order of magnitude) at any redshift with respect to observations. The HOD predicted by the simulations is remarkably in agreement with the observations. But due to the low SF activity of galaxies in massive halos, the models predict also a lower total stellar mass in groups with respect to the observed one at any redshift. In order to compare the SF activity level of galaxies in different environment, we also define a sample of field galaxies and “filament-like” galaxies. This is done by using the galaxy density field to find isolated galaxies (field) and galaxies in high density region but not associated to any group or more generically to an X-ray extended emission. These two classes of environment in addition to the galaxy group sample are used to study the location of galaxies in SFR-mass plane since z~1.1 as a function of the environment. Indeed, several studies have already shown there is a tight correlation between the SFR and the stellar masses of the bulk of the star forming galaxy population at least over the past 10 Gyr. Quiescent galaxies are mainly located under this main sequence (MS) and in a more scattered cloud. Our analysis shows that the Main Sequence of star forming galaxies in the two redshift bins considered (0.15 < z < 0.5 and 0.5 < z < 1.1) is not a linear relation but it shows a flattening towards higher masses (M* > 10^10.4−10.6 M_sun). Above this limit, the galaxy SFR has a very weak dependence on the stellar mass. This flattening, to different extent, is present in all environments. At low redshift, group galaxies tend to deviate more from the mean MS towards the region of quiescence with respect to isolated and filament-like galaxies. This environment dependent location of low redshift group galaxies with respect to the mean MS causes the increase of the dispersion of the distribution of galaxies around the MS as a function of the stellar mass. At high redshift we do not find significant evidence for a differential location of galaxies with respect to the MS as a function of the environment. Indeed, in this case we do not observe a significant increase of the dispersion of the distribution of galaxies around the MS as a function of the stellar mass. We do not find evidence for a differential distribution in the morphological type of MS galaxies in different environments. Instead, we observe a much stronger dependence of the mean S´ersic index on the stellar mass. These results suggest that star formation quenching in group galaxies is not due to galaxy structural transformations. It also suggests that while morphology of MS galaxies is more stellar mass dependent, star formation quenching is mostly environment dependent. We conclude that the membership to a massive halo is a key ingredient in the galaxy evolution and that this acts in terms of star formation quenching in group sized halos.

Semiconducting single-walled carbon nanotubes (CNTs) exhibit a chirality depended band structure of a one-dimensional lattice. Due to the radiative recombination of excitons CNTs emit photoluminescence in the near and mid infrared ranges depending on the tube diameter. Excitons are subject to diffusion along the tube before radiative recombination. Thereby they probe sites that give rise to spin-flips or non-radiative decay, or, at cryogenic temperatures, they localize in zero-dimensional quantum dots at the minima of the local energy potential landscape. Thus, the optical spectroscopy of individual CNTs probes not only the intrinsic exciton dynamics, like diffusion and intrinsic life-time, but also disorder of the CNT lattice and its environment. Intrinsic and extrinsic inhomogeneities and impurities may give rise to photoluminescence quenching, brightening of dark exciton states or generation of charged exciton complexes. In the framework of this thesis the physics of excitons in CNTs was investigated in two ways: On the one hand their environment was varied with an static electric field, on the other hand the CNTs were isolated from their environment. A comprehensive set of optical spectroscopy techniques was used to study individual CNTs at low temperatures. This included photoluminescence excitation, (time-resolved) photoluminescence, and photon correlation spectroscopy. This work identified exciton localization as predominant feature of individual CNTs at cryogenic temperatures. CNTs on substrate exhibited asymmetric line shapes at low temperature and temperature dependent shifts on the PL energy. Moreover for constant temperature, PL energies were subject to spectral diffusion, which arose - in analogy to compound semiconductor quantum dots - from interaction with a few close charge fluctuators in the dielectric environment. In addition, evidence for exciton localization was provided by the non-classical photon emission statistics of cryogenic CNTs. The main focus of this thesis was the study of individual CNTs in a static electric field. A metal-oxide-semiconductor device was used to probe for the transverse polarizability of excitons. In consequence, the PL energy of CNTs exhibited red-shifts as a quadratic function of the perpendicular electric field. However, a subclass of CNTs was characterized by satellite peaks in the emission profile. By their energy splitting they were assigned to PL emission from dark exciton states, e.g. triplet and k-momentum excitons, and resulted presumably from impurity induced symmetry breaking. As a function of the electric field, CNTs with a broken symmetry featured linear shifts of the PL energy of bright and triplet excitons. A third energy scale in the exciton fine structure was manifested by CNTs that exhibited the emergence of a satellite peak as a function of the electric field. These satellites were assigned to the PL of trions generated by doping of individual CNTs with charges from close oxide states. Presumably such close charge states played also an important role in the variation of the excitation spectra of individual CNTs, which was observed as a function of the applied electric field. This variation could be mediated by switching of charge states, which varied the localization potential of excitons. Finally, the extrinsic effects of the surrounding dielectric medium were contrasted by the remarkable optical properties of as-grown suspended CNTs. Freely suspended CNTs featured isolated localized excitons with narrow linewidths, intrinsic exciton lifetime and a significantly increased quantum yield. Moreover, they lack signatures of spectral diffusion or intermittency even on the shortest timescales.

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Das Gebiet der Nichtgleichgewichtsdynamik stark korrelierter Quantensysteme beinhaltet eine Vielzahl interessanter Fragestellungen, erweist sich dabei allerdings oftmals als schwer zugänglich für gängige numerische und analytische mathematische Methoden. In den letzten Jahren hat sich durch die experimentelle Realisierung gut kontrollierbarer quantenmechanischer Systeme die Möglichkeit eröffnet, Experimente als Quantensimulatoren für das Verhalten komplexer Vielteilchensysteme zu benutzen. Ultrakalte Atome in optischen Gittern eignen sich hervorragend als Simulatoren für simple Festkörpersysteme, da sich sämtliche Parameter der zugrunde liegenden Hamiltonoperatoren präzise kontrollieren lassen und der Zustand der Systeme mit einer Vielzahl an Messmethoden untersucht werden kann. In unseren Experimenten realisieren wir Bose-Hubbard Systeme durch ultrakalte 39K Atome in blau verstimmten optischen Gittern. Zusätzliche optische Dipolpotenziale und magnetische Feshbach-Resonanzen erlauben es uns dabei, die Parameter der Systeme zu jedem Zeitpunkt beliebig zu variieren. Dadurch sind die von uns erzeugten Systeme in besonderem Maße dazu geeignet, Nichtgleichgewichtseffekte zu untersuchen. Unser Hauptaugenmerk liegt auf der Untersuchung der Expansionsdynamik wechselwirkender Atome in homogenen Gittern. Wir beginnen unsere Experimente mit einem Anfangszustand im tiefen Gitter, der aus lokalisierten Atomen auf maximal einfach besetzten Gitterplätzen besteht. Durch gleichzeitiges schnelles Verringern der Gittertiefe und der externen Potenziale werden die Atome in ein homogenes Gitter entlassen und die Zeitentwicklung ihrer Dichteverteilung wird durch Absorptionsabbildungen festgehalten. Es zeigt sich, dass sowohl die Wechselwirkung zwischen den Atomen als auch die Dimensionalität der Gitter einen starken Einfluss auf die Dynamik haben. In allen integrablen Grenzfällen des Bose-Hubbard Modells verhalten sich die Atome ballistisch und expandieren mit hoher Geschwindigkeit, doch sobald sich das System außerhalb der integrablen Regime befindet verringert sich die Expansionsgeschwind-igkeit drastisch. Diese verringerte Geschwindigkeit geht einher mit der Ausbildung charakteristischer bimodaler Dichteverteilungen, die auf eine diffusive Dynamik schließen lassen. Für stark wechselwirkende Systeme können wir einen dimensionalitätsabhängigen Übergang zwischen ballistischer Dynamik im 1D hard-core-regime und diffusiver Dynamik im 2D Fall beobachten sowie eine starke Verringerung der Expansionsgeschwindigkeit, wenn der Anfangszustand des Systems mehrfach besetzte Gitterplätze enthält. Des Weiteren beobachten wir die Erzeugung solcher Mehrfachbesetzungen nach dem Entlassen der Atome, deren schnelle Entwicklung auf eine lokale Relaxationsdynamik hin zu quasistationären Werten deuten lässt. Als Letztes untersuchen wir die Entwicklung der Quasiimpulsverteilung stark wechselwirkender expandierender Atome, die laut theoretischer Vorhersagen eine vorübergehende Quasikondensation zeigen sollen, bei der sich scharfe lokale Maxima in der Quasiimpulsverteilung bei endlichen Quasiimpulsen bilden. Wir beobachten die Entstehung nicht-thermischer Quasiimpulsverteilungen die Maxima an den vor-hergesagten Positionen zeigen. Allerdings sind die von uns beobachteten Maxima wesentlich breiter als die vorhergesagten und wir diskutieren eine Reihe möglicher Erklärungen für diese Verbreiterung sowie Vorschläge zur Verbesserung zukünftiger Experimente. / The field of non-equilibrium dynamics of strongly correlated quantum systems encompasses some of the most interesting questions about quantum mechanical behavior, but is particularly challenging for established numerical methods. However, recent advances in the experimental control over certain quantum mechanical systems have paved the way towards the quantum simulation of dynamics previously beyond the reach of theoretical investigations. Among the most successful candidates for the implementation of quantum simulators are ultracold atoms in optical lattices, which combine an excellent control over the Hamiltonians governing their evolution with a multitude of methods to measure a diverse range of observables. In our experiments, we use ultracold 39K atoms in blue-detuned optical lattices to implement Bose-Hubbard systems. Employing optical dipole potentials to adjust the external confinement as well as Feshbach resonances to change the interaction strength between the atoms, we are able to control all parameters of the Bose-Hubbard Hamiltonian individually and in real-time, which makes our setup particularly well suited to investigate the time evolution of non-equilibrium systems in a wide range of parameter regimes. Our main experimental results are concerned with the expansion dynamics in homogeneous Hubbard systems. We create initial states of localized atoms in a deep lattice, described by a product of Fock states with no more than one atom per lattice site. These atoms are released into homogeneous lattices by simultaneous quantum quenches in the external confinement as well as the tunneling coupling along the expansion directions. We find that both dimensionality and interaction strength crucially influence the non-equilibrium dynamics. While the atoms expand ballistically in all integrable limits of the Bose-Hubbard model, deviations from these limits dramatically suppress the expansion and lead to the appearance of almost bimodal cloud shapes, indicating diffusive dynamics in the center surrounded by ballistic wings. For strongly interacting bosons, we observe a dimensional crossover of the dynamics from ballistic in the one-dimensional hard-core case to diffusive in two dimensions, as well as a strong suppression of the expansion dynamics upon introducing higher occupancies into the initial state. Furthermore, we investigate the fast relaxation of the system after the sudden quenches and observe a buildup of higher occupancies on a timescale of less than a tunneling time, indicative of local relaxation to quasi-equilibrium values. Finally, we also study the evolution of the quasimomentum distribution of expanding 1D hard-core bosons, which is predicted to acquire sharp peaks at finite quasimomenta while the system undergoes a transient dynamical quasi-condensation. We do observe the formation of a non-thermal quasimomentum distribution with peaks at the correct quasimomenta. However, these peaks are much broader than those predicted by theory. Thus, we discuss multiple possible effects that could hinder the formation or detection of quasi-condensation, as well as methods to experimentally investigate and mitigate these issues.