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Solar hydrogen production via water splitting promises to sustainably produce clean fuel for various applications by primarily relying on two of the most abundant resources on Earth, sunlight and water. Photocatalysis is one of the technologies that has attracted increasing research interest for water splitting, along with the degradation of organic pollutants and the synthesis of value-added organic products. Experimental approaches rely on suitable light-active compounds that catalyze the respective chemical reactions which mainly occur in a solution of a substrate mixture. In modern catalysis, metal nanoparticles (MNPs) excel as (co)catalysts in various organic reactions due to their synergistic effects on catalytic performance. By the same token, MNPs are being explored in photocatalysis. However, obtaining detailed insights into the photocatalytic mechanism typically requires state-of-the-art experimental techniques, such as angle-resolved photoemission spectroscopy (ARPES). While these techniques provide a wealth of data, their interpretation can be challenging: On the one hand, the underlying photophysical and electronic phenomena are of complicated quantum nature. On the other hand, viable system designs must meet additional requirements, such as preventing the aggregation of MNPs, which adds to the multi-faceted nature of the systems. Therefore, it has proven expedient to use experimental and theoretical methods to characterize photocatalytic systems jointly. Due to its favorable ratio of accuracy to computational cost, ab-initio density-functional theory (DFT) in its standard Kohn-Sham formulation is currently the most popular electron-structure method in photocatalysis and, moreover, in most interdisciplinary fields of physics with chemistry, biology, and materials science. This thesis's first of two project lines concerns predicting structural, electronic, and photophysical properties of molecular building blocks of (photo)catalytic systems containing MNPs using ground-state DFT and time-dependent DFT (TDDFT). A primary focus lies on understanding performance-related differences between certain cocatalytic MNP species (Ni, Pd, Pt) found in photocatalytic experiments for hydrogen production. Regarding the conceptual basis, I first present a DFT-based procedure to obtain low-energy molecular structures of systems containing MNPs, since these generally exhibit many geometries that are stable and similar in energy. This procedure is first applied to investigate whether MNPs and solvents interact (significantly). Studying small Pd nanoparticles (clusters) in solution with ketones shows that the interaction can affect the electronic and molecular structure of the metal particles. The interaction manifests itself, \textit{inter alia}: (i) In changes in the electronic density of states of the metal-solvent systems near the Fermi level (compared to their components). (ii) In the quenching of the magnetic moment that Pd clusters otherwise exhibit in the gas phase. The results suggest that the electronic interaction is more pronounced with aromatic than non-aromatic solvents. In the course of a collaboration of physics and chemistry in a joint research center (SFB840, "From Particulate Nanosystems to esotechnology"), we explore new design strategies in photocatalytic hydrogen production to replace cocatalytic noble MNPs with earth-abundant Ni: These novel approaches utilize the metal-organic framework MIL-101 to combine MNPs with either an Ir-based molecular photosensitizer or solid-state photocatalysts CdS, CdS/TiO2 without surface blocking ligands. The former enables hydrogen production via proton reduction in water under visible light. Encapsulating the MNPs, and photosensitizer into the nanopores of MIL-101 prevents metal aggregation. CdS/TiO2 and CdS decorated with MNPs accomplish the visible light-driven acceptorless dehydrogenation of alcohols and benzylamine under liberation of hydrogen, respectively. The MNPs reduce charge recombination and stabilize the CdS component against photooxidation. In most cases, the combination with MNPs promotes hydrogen production compared to the pure photosensitizer and photocatalyst, respectively. Encouragingly, Ni promotes hydrogen evolution in all cases, consistently outperforming the paradigmatic noble metals Pd and Pt. My studies contribute to a first understanding of the general role of MNPs and the synergistic effects of Ni in these systems: (i) DFT calculations reveal that the Ir photosensitizer and the substrates (benzyl alcohol, benzylamine) bind stronger to Ni than to the noble metal clusters. (ii) TDDFT calculations with optimally tuned range-separated hybrid functionals show that all three metals directly impact the photophysical properties of the photosensitizer via electronic interaction. The respective optical excitations feature a pronounced charge transfer from the metal cluster to the photosensitizer. The second project line focuses on pump-probe ARPES. This technique is a powerful tool for characterizing the photoactivated state of materials, as it allows direct insights into the excited electronic structure. Here, I develop a method for predicting pump-probe ARPES from molecular systems using TDDFT in real space and real time. To this end, I present a method that unites the key elements of this technique - excitation, ionization, and detection - in a single TDDFT simulation. I first provide a proof of concept. Finally, studying the organic semiconductor molecule perylene-3,4,9,10-tetracarboxylic dianhydride shows that this approach accomplishes the challenging task of capturing many-body signatures of excitations. In other words, this method goes beyond the popular DFT-based single-particle interpretation of ARPES (experiments), and this study provides an example of when many-particle effects are so prominent that they cannot be disregarded. Overall, this method constitutes a viable extension to existing methods that can now be utilized to interpret many-particle effects in pump-probe experiments.

The language picture of the world, as a result of the constantly evolving linguistic spiritual activity of man, is fixed in the language, its semantics, and also in the language system results and features of man’s cognition of the surrounding world and of himself as a whole are imprinted. The picture of the world can not be performed in a language that is unfamiliar to man, just as it can not include phenomena unknown and not realized by man. Therefore, at present, linguistic studies related to the study of concepts and conceptual fields in diachronic and synchronic aspects are so relevant. These studies are based on data from various dictionaries, such as historical, explanatory, phraseological, dialectal, etymological, word-building, etc. In this article, we consider the fixation of the lexeme ‘to sulk’ in the etymological, historical, dialectal, explanatory dictionaries of the Russian language and dictionaries of synonyms. Language analysis of the lexeme allows us to establish the peculiarities of the lexical and semantic scope of this definition in different historical epochs, as well as to trace the diachronic and synchronic development of the language as a whole. A detailed examination of the lexico-semantic volume of the verb in question makes it possible to more accurately determine its meaning in the context of literary monuments. On the basis of the data obtained as a result of the analysis of a sufficient number of linguistic material, it is possible to draw certain conclusions: 1) the verb under study is of ancient Pro-Slavic origin, 2) with the development of the language, the semantic volume of the lexeme is gradually expanding, 3) the largest number of meanings is recorded in the dictionary of the modern Russian literary language

An essay of Jan Patočka on Dostoevsky's short story "The Dream of a Ridiculous Man".

It is a particularly challenging task in stereochemistry to determine the absolute configuration of chiral molecules, i.e. to assign to a given sample the microscopic enantiomeric structure. In recent years, Coulomb Explosion Imaging (CEI) has been shown to yield directly the absolute configuration of small molecules in the gas phase. This contribution describes the experimental basics of this approach, highlights the most significant results and discusses limitations. A short discussion on extending Coulomb Explosion Imaging beyond analytic aspects to fundamental questions of molecular chirality concludes this review.

Contrary to the standard view in the Kant literature, I argue that the concept of “existence” is the real focus of Kant’s investigation in the “First Moment” of the “Analytic of the Beautiful” in the Critique of the Power of Judgment. That is, “existence” is not a secondary or subordinate part of a more general discourse concerning the “disinterestedness of aesthetic judgment”. Rather, the whole characterization of the judgment of taste as a “judgment of an object grounded on a delight in it which is without any interest” shall be considered here as a means to constructing a new definition of the modal concept of “existence”. More generally, the four moments of the “Analytic of the Beautiful” contain preliminary work on the modal concepts of existence, possibility, necessity — and, of course, contingency, which is very important because it is required for the definition of the very special modal status of the “maxims of judgment”.

SummaryThe aim of this article is to show that, in his use of the word ‘representation’, Philip Kitcher is committed to a particular notion of representation, which is essential to his argument for Real Realism in his paper Real Realism: The Galilean Strategy (Real Realism herinafter). After a short presentation of Kitcher’s original argument for Real Realism, I show that Kitcher’s notion of representation is not indisputable. By producing an alternative version of Kitcher’s argument, one which does not rely on this term ‘representation’, I show the force and functioning of the Galilean strategy itself. A comparison of the two formulations of the argument reveals what is additionally brought in by Kitcher’s notion of representation: specifically, a particular answer to the question of what truth consists in. This presumed correspondence theory of truth is needed to achieve Real Realism by the Galilean strategy. The positive upshot is, however, that one can support the Galilean strategy as such, without being a Real Realist: One can apply the strategy to any other conception of truth.

Hodgkin and Huxley were the pioneers to abstract biological neuron as an electric circuit and nerve signal as the voltage impulse. The Hodgkin-Huxley theory (Hodgkin and Huxley, 1952) has set the direction and defined the goals for much of the ensuing research in biophysics. However, in 2005, T. Heimburg and A. D. Jackson, biophysicists from Copenhagen proposed a new neural theory called Soliton theory (Heimburg and Jackson, 2005). In this theory, the nerve conduction is proposed as a density wave. In this paper, Hodgkin-Huxley and Soliton theories are described and a theoretical comparison has been carried out throughout the analysis of the theories and models.

In this article, we review recent theoretical works on the Schwingermechanism of particle production in external electrical fields. Although the non-perturbative Schwinger mechanism is at the center of this discussion, many of the approaches that we discuss can cope with general time and space dependent fields, and therefore also capture the perturbative contributions to particle production., Review for Progress in Particle and Nuclear Physics. 76 pages, 36 figures

Two PhD theses (Alexander Gordienko, 1912; Johannes Angerstein, 1914) and a dissertation in partial fulfillment of a PhD thesis (H. S. French, Zurich, 1914) are reviewed that deal with hitherto unpublished UV-vis spectroscopy work of coordination compounds in the group of Alfred Werner. The method of measurement of UV-vis spectra at Alfred Werner's time is described in detail. Examples of spectra of complexes are given, which were partly interpreted in terms of structure (cis ? trans configuration, counting number of bands for structural relationships, and shift of general spectral features by consecutive replacement of ligands). A more complete interpretation of spectra was hampered at Alfred Werner's time by the lack of a light absorption theory and a correct theory of electron excitation, and the lack of a ligand field theory for coordination compounds. The experimentally difficult data acquisitions and the difficult spectral interpretations might have been reasons why this method did not experience a breakthrough in Alfred Werner's group to play a more prominent role as an important analytical method. Nevertheless the application of UV-vis spectroscopy on coordination compounds was unique and novel, and witnesses Alfred Werner's great aptitude and keenness to always try and go beyond conventional practice.

Zeno’s arguments are generally regarded as ingenious but downright unsound paradoxes, worth of attention mainly to disclose why they go wrong or, alternatively, to recognise them as clever, even if crude, anticipations of modern views on the space, the infinite or the quantum view of matter. In either case, the arguments lose any connection with the scientific and philosophical problems of Zeno’s own time and environment. In the present paper, I argue that it is possible to make sense of Zeno’s arguments if we recognise that Zeno was indeed a close follower of Parmenides, who wanted to show that, if the plurality of beings existed, then various absurd consequences would follow. He intended to highlight the compact and inarticulate nature of the being, and the human character of the system of world partitions producing the entities and the objects on which our knowledge is based.

Im Rahmen dieser kumulativen Doktorarbeit werden Studien mit sichtbarem Licht und Terahertzlicht an Halbleiter-Quantenfilmen beschrieben, wobei Experimente mit Hilfe einer mikroskopischen Theorie analysiert werden. Nach einer Einleitung in Kapitel 1 werden die theoretischen Grundlagen in Kapitel 2 dargelegt. Hiernach folgt die Beschreibung von zwei Arten von Experimenten: In Kapitel 3 wird Terahertzspektroskopie an Quantenfilmen beschrieben, bei denen das sichtbare Licht in erster Linie mit den Quantenfilmen wechselwirkt. In Kapitel 4 besteht zusätzlich eine starke Kopplung des sichtbaren Lichtes mit einer Kavität. Beide Themen sind aufgrund der Ähnlichkeiten von Exzitonen mit atomaren Systemen von grundsätzlichem Interesse. Ein sehr fundamentaler Effekt, der beide Themen verbindet, ist der AC-Stark-Effekt: Er beschreibt das Aufspalten von Spektrallinien durch die Anwesenheit eines elektrischen Feldes. In Atomen wird dies Rabiaufspaltung genannt. Kapitel 3 beschreibt Experimente mit terahertzinduzierter Rabiaufspaltung. In Kapitel 4 wird Terahertzspektroskopie an Exziton-Polaritonen beschrieben. Diese entstehen, wenn Quantenfilme an eine Kavität koppeln. Die 1s-Exzitonenresonanz spal- tet auf in tiefere und höhere Exziton-Polaritonen. Eine Zusammenfassung und ein Ausblick werden in Kapitel 5 gegeben., In this Thesis, studies with optical and terahertz light on semiconductor quantum wells are presented. Experiments are analyzed by means of a microscopic theory. A short introduction in chapter 1 is followed by the theoretical basis in chapter 2. After, two kinds of experiments are shown: Chapter 3 is devoted to terahertz spectroscopy on bare quantum wells. In chapter 4, the optical light couples in addition to a micro cavity. Both topics are of fundamental interest due to the similarity of excitons with atomic systems. A basic effect connecting both topics is the AC Stark effect: It describes the splitting of spectral lines due to the presence of an electric field. For atomic systems, this is called Rabi splitting. Chapter 3 describes experiments with terahertz-induced Rabi splitting. In chapter 4, terahertz spectroscopy on exciton-polaritons is described. These appear due to the coupling of the quantum wells to a micro cavity: The 1s-exciton resonance splits into lower and higher exciton-polaritons. Concluding remarks and a short outlook are given in chapter 5.

Ten years ago, we began a new research effort in attoscience at ETH Zurich, building on our ultrafast laser expertise in the few femtosecond regime. I present some of the technical highlights and explain how we continue within the NCCR MUST.

Zusammenfassung (PDF-Dokument) Abstract (PDF-Dokument)

Glasbeno-analitični nastavki: med idejo in strukturo

An effort of proponents of relativity theory to find evidence for the so-called gravitational red-shift of spectral lines as one of the experimental consequences of Einstein's generalized theory of relativity is reconsidered with reference to hitherto unpublished documents. It is shown how much interest Albert Einstein in fact took, around 1920, in the data analysis of Leonhard Grebe and Albert Bachem, who tried to explain why most earlier efforts to find the gravitational red-shift had failed. They carefully measured the line profiles of the spectral lines both in the sun's Fraunhofer lines and in pressure-independent laboratory comparison spectra. Then they rejected all lines with strong neighbouring lines which could cause apparent shifts of the line centres; the remaining seven well-isolated lines showed the gravitational red-shift with acceptable accuracy. Nevertheless, their claim to have successfully isolated the relativistic effect never convinced the astrophysicists of their day - the reasons for the scientific community's scepticism, contrasted against the enthusiastic group of Einstein sympathizers, are also discussed.

The idea put forward in I that also such algebras which do not fulfil the axiom of powerassociativity may allow in some cases physical interpretation, is illustrated by a mathematical model showing properties similar to the Cartesian coordinates of a particle.

Some experimental data concerning the backward α-12C elastic scattering around 20 MeV are analysed on the basis of a "one Regge pole" model. This model gives a rather satisfactory representation of the main characteristics of the phenomenon and it appears possible to make definite predictions concerning the resonant α-12C system. We also indicate the experimental data needed in order to investigate the model from a more quantitative view point. © 1966., SCOPUS: ar.j, info:eu-repo/semantics/published