Refine
Has Fulltext
- yes (106)
Is part of the Bibliography
- yes (106)
Year of publication
Document Type
- Preprint (106) (remove)
Language
- English (106) (remove)
Keywords
- boron (20)
- Quran (8)
- diborenes (8)
- Koran (7)
- Text Mining (7)
- crystallization (6)
- carbenes (5)
- cosmology (5)
- qubit (5)
- Boron (4)
- Positronen-Emissions-Tomografie (4)
- XML (4)
- decoherence (4)
- Bayesian classifier (3)
- PET (3)
- Softwarearchitektur (3)
- Textvergleich (3)
- Visualisierung (3)
- Wissensmanagement (3)
- diboranes (3)
- diborene (3)
- low-valent compounds (3)
- prostate cancer (3)
- 18F-DCFPyL (2)
- Base text (2)
- CSS (2)
- Cascading Style Sheets (2)
- Content Management (2)
- DFT calculations (2)
- Diborane (2)
- Fluoreszenz (2)
- Gothenburg model (2)
- Knowledge Management (2)
- Maschinelles Lernen (2)
- Meta-model (2)
- N-heterocyclic carbenes (2)
- Nonadiabatic quantum dynamics (2)
- PSMA (2)
- PSMA-RADS (2)
- RADS (2)
- SSTR (2)
- Strahlungstransport (2)
- Supraleiter (2)
- Text mining (2)
- Textual alterations weighting system (2)
- Textual document collation (2)
- Visualization (2)
- Wrapper <Programmierung> (2)
- Zeitrichtung (2)
- bond activation (2)
- borylation (2)
- borylene (2)
- complexity (2)
- diborynes (2)
- emergent time (2)
- evolution (2)
- low-valent main group chemistry (2)
- modified inflation (2)
- multiple bonding (2)
- phase transition (2)
- prostate-specific membrane antigen (2)
- protein folding (2)
- qubit interaction (2)
- time-resolved photoelectron spectroscopy (2)
- transition metal complex (2)
- 1,2-additions (1)
- 2Dimensionale Spektroskopie (1)
- 3D cultures (1)
- 68Ga-DOTANOC (1)
- 68Ga-DOTATATE (1)
- 68Ga-DOTATOC (1)
- 7,8-dihydroxyflavone (7,8-DHF) (1)
- AMP-activated protein kinase (AMPK) (1)
- Analysis of RNA Modifications (1)
- Anorexia nervosa (1)
- Aromaticity (1)
- Barbituric Acid Merocyanines (1)
- Bayes-Klassifikator (1)
- Bedeutung (1)
- Beige adipocytes (1)
- Beobachter (1)
- Berechnungskomplexität (1)
- BioID (1)
- Biradicals (1)
- Bor (1)
- Boranes (1)
- Borylene (1)
- C-H activation (1)
- C/EBP (1)
- CH activation (1)
- CMR (1)
- CO activation (1)
- CO2 fixation (1)
- Causes of revelation (1)
- Chapters arrangement (1)
- Chemical Structure (1)
- Chronology of revelation (1)
- Clustering (1)
- Computational Chemistry (1)
- Computersimulation (1)
- Crystal structure of MTR1 (1)
- Cycloaddition (1)
- DFT mechanism (1)
- DNA (1)
- DNA catalyst (1)
- DNA-based nanostructures (1)
- DNA-processing enzymes (1)
- Deep learning (1)
- Diboranes (1)
- Diborene (1)
- Doppelquantenkohärenz (1)
- E8 symmetry (1)
- EEA (1)
- Entscheidung (1)
- Entscheidungen (1)
- Evolution (1)
- Excited state dynamics (1)
- Exciton (1)
- Exciton dynamics (1)
- Exciton localization dynamics (1)
- Exziton (1)
- Fragmentation (1)
- Fragmentierung (1)
- Frames (1)
- Fundamentalkonstante (1)
- Gothenburg Modell (1)
- Gothenburg model of collation process (1)
- Gödel (1)
- HHV-6 (1)
- HTML (1)
- Helicene diimide (1)
- Herpesvirus (1)
- High-Throughput Sequencing Method, DZ-seq (1)
- Higher-order Transient Absorption Spectroscopy (1)
- Hurwitz theorem (1)
- Hydrocarbon radicals (1)
- Hydrocarbons (1)
- Hydrogen (1)
- Information Visualization (1)
- Inverse Probleme (1)
- JSF (1)
- Java Frameworks (1)
- Knowledge Management System (1)
- Knowledge Modeling (1)
- Knowledge representation (1)
- Knowledge-based System (1)
- Kolmogorov-Komplexität (1)
- Komplex <Algebra> (1)
- Komplexität (1)
- Lawhul-Mahfuz (1)
- Lee Smolin (1)
- Lewis acids (1)
- Lewis-base adducts (1)
- Ljapunov-Funktion (1)
- Low energy electron microscopy LEEM (1)
- MI-RADS (1)
- MVC <Software> (1)
- Main-group chemistry (1)
- Mashup (1)
- Mashup <Internet> (1)
- Metadynamics (1)
- Metal clusters (1)
- Metallocene (1)
- Metallocenes (1)
- Methyltransferase Ribozyme (1)
- Methyltransferase Ribozyme MTR1 (1)
- Molekülzustand (1)
- Monte Carlo simulation (1)
- Multiple bonding (1)
- Multiple bonds (1)
- Myocardial infarction (1)
- N6-methyladenosine (1)
- N6-methyladenosine (m6A) (1)
- NMR spectroscopy (1)
- Natur (1)
- Nature constants (1)
- Naturgesetz (1)
- Natürliche Auslese (1)
- Naïve Bayesian (1)
- Nicht-Transparente Medien (1)
- Non-transparency (1)
- Nonadiabatic dynamics (1)
- Nucleobase Surrogate Incorporation (1)
- Optische Spektroskopie (1)
- Organoboron chemistry (1)
- Overlapping (1)
- PDXP inhibitors (1)
- PET/CT (1)
- PROMISE (1)
- PSMA-PET (1)
- PSMA-RADS-3A (1)
- PSMA-RADS-3B (1)
- PSMA-targeted PET (1)
- Pancreas (1)
- Photodynamics (1)
- Photoemission electron microscopy PEEM (1)
- Photoresponsive DNA Crosslinker (1)
- Physikalische Zeit (1)
- Place of revelation (1)
- Pontryagin maximum principle (1)
- Positron Emission Tomography (1)
- Processing Model (1)
- Processing model (1)
- Prostate Cancer (1)
- Protein kinase D1 (PKD1) (1)
- RNA (1)
- RNA Aptamer (1)
- RNA Enzymes (1)
- RNA modification (1)
- RNA-Cleaving Deoxyribozymes (1)
- RNA-catalyzed RNA methylation (1)
- Reconstruction of original text (1)
- Reference Architecture (1)
- Ribozyme-catalyzed RNA labeling (1)
- SQH method (1)
- SSTR-RADS (1)
- Scar (1)
- Scatter Plot (1)
- Segmentation (1)
- Singapore (1)
- Single-molecule microscopy (1)
- Software architecture (1)
- Software design (1)
- Spatially resolved 2D spectroscopy (1)
- Spektroskopie (1)
- Spring (1)
- Stages of Prophet Mohammad’s messengership (1)
- Stammzelle (1)
- Statistical classifiers (1)
- Streptavidin (1)
- Struts (1)
- Support Vector Machine (1)
- Tetrafluorodiborane (1)
- Text categorization (1)
- Text segmentation (1)
- Time hole (1)
- Time-resolved photoemission electron microscopy (1)
- Tolane-Modified Fluorescent Nucleosides (1)
- Transition metals (1)
- Two-color pump-probe spectroscopy (1)
- Ultrafast spectroscopy (1)
- Virchow Node (1)
- Visual Text Mining (1)
- Web service (1)
- Webservice Composition (1)
- Wissensbanksystem (1)
- Wissensrepräsentation (1)
- Wrapper (1)
- Wrappers (1)
- X-ray crystallography (1)
- XML model (1)
- YTH reader proteins (1)
- Zweidimensionale Spektroskopie (1)
- [177Lu]-DOTATATE/-DOTATOC (1)
- [68Ga] (1)
- alkene-alkyne [2+2] photocycloaddition (1)
- alkynes (1)
- amine borane dehydrocoupling (1)
- animal research (1)
- antibody fluorescence signals (1)
- atomic mutagenesis (1)
- attention (1)
- auditory (1)
- auditory domain (1)
- benzyl radical (1)
- bit (1)
- boron chains (1)
- boronium cations (1)
- borylenes (1)
- brain activity (1)
- carbohydrates (1)
- carbon dioxide (1)
- cardiomyocytes (1)
- carsharing (1)
- catalysis (1)
- chain structures (1)
- chalcogens (1)
- chelates (1)
- conewise linear systems (1)
- conical intersections (1)
- conjugation (1)
- converse Lyapunov theorems (1)
- covalent and site-specific RNA labeling (1)
- crystal growth (1)
- crystallography (1)
- cyclic (alkyl)(amino)carbene (1)
- cycloaddition (1)
- decision (1)
- demethylase enzymes FTO and ALKBH5 (1)
- density functional calculations (1)
- deoxyribozymes (1)
- desymmetrization (1)
- diboraindanes (1)
- diborane (1)
- diborane(6) (1)
- diboration (1)
- diboron (1)
- diboryne (1)
- diradicals (1)
- discrete-time systems (1)
- distance-based classifier (1)
- disturbance (1)
- early cosmology (1)
- electron donors (1)
- electrophiles (1)
- elektronisch angeregte Zustände (1)
- emergent gravity (1)
- energy transfer dynamics (1)
- erovalent diboron compounds (1)
- exciton dynamics (1)
- exciton-exciton (1)
- eye blinks (1)
- fatty acid (1)
- field-induced surface hopping (1)
- fine-tuning (1)
- fluorescence (1)
- fluorescence quantum yield (1)
- fluorescent protein (1)
- fluorescent resonance energy transfer (1)
- free movement (1)
- fusion and fission (1)
- gastrointestinal disease (1)
- half-sandwich complexes (1)
- helicobacter (1)
- heterocycles (1)
- heuristics (1)
- hiPSC-CM (1)
- hydration dynamics (1)
- hydroarylation (1)
- hydroboration (1)
- hydrogenation (1)
- immunofluorescence detection (1)
- in vitro selection (1)
- in vitro selection from a structured RNA library (1)
- induced pluripotent stem cells (1)
- inflammatory bowel disease (1)
- inflation (1)
- infrared-spectra (1)
- insertion (1)
- interactive collation of textual variants (1)
- intermolecular applications of ribozymes (1)
- interobserver (1)
- interreader (1)
- iodine (1)
- isomers (1)
- large Stokes shift (1)
- latency (1)
- ligand exchange (1)
- light-induced interstrand DNA crosslinking (1)
- loop quantum gravity (1)
- low-valent main-group species (1)
- main-group chemistry (1)
- mapping function (1)
- meaning (1)
- miR-30 (1)
- miRNA processing (1)
- microbiota (1)
- mitochondria (1)
- mobility (1)
- modified nucleosides (1)
- multiple bonds (1)
- multiverse (1)
- near-IR chromophores (1)
- neuroendocrine neoplasia (1)
- neuroendocrine tumor (1)
- nnU-net (1)
- non-smooth optimization (1)
- nonadiabatic dynamics (1)
- nonconvex optimization (1)
- norovirus (1)
- observer (1)
- oddball (1)
- organoid culture (1)
- phase space (1)
- photodynamics (1)
- physical time (1)
- pi-conjugation (1)
- position-specific installation of m1A in RNA (1)
- protein hydration (1)
- protein localization (1)
- pyrene dimer (1)
- pyridoxal phosphatase (PDXP) (1)
- quantum computing (1)
- rBAM2-labeled RNA strands (1)
- reactive intermediates (1)
- rearrangement (1)
- recording methods (1)
- redox reactions (1)
- reductive coupling (1)
- refeeding syndrome (1)
- reporting and data system (1)
- ring expansion (1)
- rotavirus (1)
- salmonella (1)
- selection (1)
- service based software architecture (1)
- service brokerage (1)
- silylenes (1)
- small HOMO-LUMO gap (1)
- small-molecule activation (1)
- somatostatin receptor (1)
- spectroscopy (1)
- squaraine polymer (1)
- stability analysis (1)
- standardized reporting (1)
- stem cell therapy (1)
- strained molecules (1)
- structural analysis (1)
- sustainability (1)
- synthesis (1)
- synthetic methods (1)
- taxi (1)
- text categorization (1)
- time hole (1)
- tracer (1)
- trans-acting 2'-5' adenylyl transferase ribozymes (1)
- trans-formanilide (1)
- transfer hydrogenation (1)
- transition metals (1)
- transport (1)
- tumor heterogeneity (1)
- type I interferon (1)
- unified theories (1)
- vegetarians (1)
- virtual reality (1)
- virus reactivation (1)
- visual (1)
- visual domain (1)
- vitamin B6 (1)
- water migration (1)
- Überlappung (1)
- β3 adrenergic receptor (ADRB3) (1)
Institute
- Institut für Anorganische Chemie (30)
- Institut für Physikalische und Theoretische Chemie (19)
- Institut für deutsche Philologie (17)
- Institut für Organische Chemie (14)
- Theodor-Boveri-Institut für Biowissenschaften (12)
- Klinik und Poliklinik für Nuklearmedizin (6)
- Physikalisches Institut (4)
- Rudolf-Virchow-Zentrum (4)
- Institut für Klinische Neurobiologie (2)
- Institut für Mathematik (2)
Sonstige beteiligte Institutionen
- Johns Hopkins School of Medicine (3)
- International Max Planck Research School Molecular Biology, University of Göttingen, Germany (2)
- Center for Nanoscale Microscopy and Molecular Physiology of the Brain (CNMPB), Göttingen, Germany (1)
- Center for Nanosystems Chemistry (CNC), University of Würzburg (1)
- Center for Nanosystems Chemistry (CNC), Universität Würzburg (1)
- Center for Nanosystems Chemistry (CNC), Universität Würzburg, Am Hubland, 97074 Würzburg, Germany (1)
- Center of Excellence for Science and Technology - Integration of Mediterranean region (STIM), Faculty of Science, University of Split, Poljička cesta 35, 2100 Split, Croatia (1)
- Charles University, Faculty of Mathematics and Physics, Ke Karlovu 5, 121 16 Prague, Czech Republic (1)
- Departamento de Química, Facultad de Ciencias, Universidad Autónoma de Madrid, 28049 Madrid, Spain (1)
- Department of Biomedical Imaging, National Cerebral and Cardiovascular Research Center, Suita, Japan (1)
- Department of Chemistry, Humboldt Universität zu Berlin, Brook-Taylor-Strasse 2, 12489 Berlin, Germany (1)
- Department of Molecular Biology, University Medical Center Göttingen, Germany (1)
- Department of Molecular Biology, University Medical Centre Göttingen, Göttingen 37073, Germany (1)
- Division of Medical Technology and Science, Department of Medical Physics and Engineering, Course of Health Science, Osaka University Graduate School of Medicine, Suita Japan (1)
- Ernst Strüngmann Institute for Neuroscience in Cooperation with Max Planck Society (ESI) (1)
- Fakultät für Physik, Universität Bielefeld (1)
- Göttingen Center for Molecular Biosciences, Georg- August University Göttingen, Göttingen 37077, Germany (1)
- Institut for Molecular Biology and CMBI, Department of Genomics, Stem Cell Biology and Regenerative Medicine, Leopold-Franzens-University Innsbruck, Innsbruck, Austria (1)
- Institut für Optik und Atomare Physik, Technische Universität Berlin, 10623 Berlin, Germany (1)
- Institute for Sustainable Chemistry & Catalysis with Boron (1)
- Institute of Physics and Center for Nanotechnology, University of Münster (1)
- Istituto di Chimica dei Composti Organometallici (ICCOM–CNR), Area della Ricerca del CNR, Via Moruzzi 1, I-56124 Pisa, Italy. (1)
- Johns Hopkins School of Medicine, The Russell H Morgan Department of Radiology and Radiological Science, Baltimore, MD, USA (1)
- Johns Hopkins University School of Medicine (1)
- LIDYL, CEA, CNRS, Université Paris-Saclay, CEA Saclay 91191 Gif-sur-Yvette France (1)
- Laboratory for Chemistry and Life Science, Institute of Innovative Research, Tokyo Institute of Technology, Yokohama 226-8503, Japan (1)
- Lehrstuhl für BioMolekulare Optik, Ludwig-Maximilians-Universität München (1)
- NanoOptics & Biophotonics Group, Experimental Physics 5, Universität Würzburg (1)
- The Chinese University of Hong Kong (1)
- The University of Sussex (1)
- Zentrum für Infektionsforschung (ZINF): Nachwuchsgruppe 2 (1)
Why is our universe so fine-tuned? In this preprint we discuss that this is not a strange accident but that fine-tuned universes can be considered to be exceedingly large if one counts the number of observable different states (i.e. one aspect of the more general preprint http://www.opus-bayern.de/uni-wuerzburg/volltexte/2009/3353/). Looking at parameter variation for the same set of physical laws simple and complex processes (including life) and worlds in a multiverse are compared in simple examples. Next the anthropocentric principle is extended as many conditions which are generally interpreted anthropocentric only ensure a large space of different system states. In particular, the observed over-tuning beyond the level for our existence is explainable by these system considerations. More formally, the state space for different systems becomes measurable and comparable looking at their output behaviour. We show that highly interacting processes are more complex then Chaitin complexity, the latter denotes processes not compressible by shorter descriptions (Kolomogorov complexity). The complexity considerations help to better study and compare different processes (programs, living cells, environments and worlds) including dynamic behaviour and can be used for model selection in theoretical physics. Moreover, the large size (in terms of different states) of a world allowing complex processes including life can in a model calculation be determined applying discrete histories from quantum spin-loop theory. Nevertheless there remains a lot to be done - hopefully the preprint stimulates further efforts in this area.
This paper discusses the categorization of Quranic chapters by major phases of Prophet Mohammad’s messengership using machine learning algorithms. First, the chapters were categorized by places of revelation using Support Vector Machine and naïve Bayesian classifiers separately, and their results were compared to each other, as well as to the existing traditional Islamic and western orientalists classifications. The chapters were categorized into Meccan (revealed in Mecca) and Medinan (revealed in Medina). After that, chapters of each category were clustered using a kind of fuzzy-single linkage clustering approach, in order to correspond to the major phases of Prophet Mohammad’s life. The major phases of the Prophet’s life were manually derived from the Quranic text, as well as from the secondary Islamic literature e.g hadiths, exegesis. Previous studies on computing the places of revelation of Quranic chapters relied heavily on features extracted from existing background knowledge of the chapters. For instance, it is known that Meccan chapters contain mostly verses about faith and related problems, while Medinan ones encompass verses dealing with social issues, battles…etc. These features are by themselves insufficient as a basis for assigning the chapters to their respective places of revelation. In fact, there are exceptions, since some chapters do contain both Meccan and Medinan features. In this study, features of each category were automatically created from very few chapters, whose places of revelation have been determined through identification of historical facts and events such as battles, migration to Medina…etc. Chapters having unanimously agreed places of revelation were used as the initial training set, while the remaining chapters formed the testing set. The classification process was made recursive by regularly augmenting the training set with correctly classified chapters, in order to classify the whole testing set. Each chapter was preprocessed by removing unimportant words, stemming, and representation with vector space model. The result of this study shows that, the two classifiers have produced useable results, with an outperformance of the support vector machine classifier. This study indicates that, the proposed methodology yields encouraging results for arranging Quranic chapters by phases of Prophet Mohammad’s messengership.
Cyclic diboranes(4) based on a chelating monoanionic, benzylphosphine linker were prepared by boron-silicon exchange between arylsilanes and B\(_2\)Br\(_4\). Coordination of Lewis bases to the remaining sp\(^2\) boron atom yielded unsymmetrical sp\(^3\)-sp\(^3\) diboranes, which were reduced with KC\(_8\) to their corresponding trans-diborenes. These compounds were studied by a combination of spectroscopic methods, X-ray diffraction and DFT calculations. PMe\(_3\)-stabilized diborene 6 was found to undergo thermal rearrangement to gem- diborene 8. DFT calculations on 8 reveal a polar boron-boron bond, and indicate that the compound is best described as a borylborylene.
The Visual Editor for XML (Vex)[1] used by TextGrid [2]and other applications has got rendering and layout engines. The layout engine is well documented but the rendering engine is not. This lack of documenting the rendering engine has made refactoring and extending the editor hard and tedious. For instance many CSS2.1 and upcoming CSS3 properties have not been implemented. Software developers in different projects such as TextGrid using Vex would like to update its CSS rendering engine in order to provide advanced user interfaces as well as support different document types. In order to minimize the effort of extending Vex functionality, I found it beneficial to write a basic documentation about Vex software architecture in general and its CSS rendering engine in particular. The documentation is mainly based on the idea of architectural layered diagrams. In fact layered diagrams can help developers understand software’s source code faster and easier in order to alter it, and fix errors. This paper is written for the purpose of providing direct support for exploration in the comprehension process of Vex source code. It discusses Vex software architecture. The organization of packages that make up the software, the architecture of its CSS rendering engine, an algorithm explaining the working principle of its rendering engine are described.
We have investigated the photodynamics of \(\beta\)-D-glucose employing our field-induced surface hopping method (FISH), which allows us to simulate the coupled electron-nuclear dynamics, including explicitly nonadiabatic effects and light-induced excitation. Our results reveal that from the initially populated S\(_{1}\) and S\(_{2}\) states, glucose returns nonradiatively to the ground state within about 200 fs. This takes place mainly via conical intersections (CIs) whose geometries
in most cases involve the elongation of a single O-H bond, while in some instances ring-opening due to dissociation of a C-O bond is observed. Experimentally, excitation to a distinct excited electronic state is improbable due to the presence of a dense manifold of states bearing similar oscillator strengths. Our FISH simulations explicitly including a UV laser pulse of 6.43 eV photon energy reveals that after initial excitation the population is almost equally spread over several close-lying electronic states. This is followed by a fast nonradiative decay on the time scale of 100-200 fs, with the final return to the ground state proceeding via the S\(_{1}\) state through the same types of CIs as observed in the field-free simulations.
Whereas the reduction of N-heterocyclic carbene (NHC)-stabilised cymantrenyldibromoboranes, (NHC)BBr\(_2\)Cym, in benzene results in formation of the corresponding diborenes (NHC)\(_2\)B\(_2\)Cym\(_2\), a change of solvent to THF yields a borylene of the form (NHC)\(_2\)BCym, stabilised through its boratafulvene resonance form.
The reductive coupling of an NHC-stabilized aryldibromoborane yields a mixture of trans- and cis-diborenes in which the aryl groups are coplanar with the diborene core. Under dilute reduction conditions two diastereomers of a borirane-borane intermediate are isolated, which upon further reduction give rise to the aforementioned diborene mixture. DFT calculations suggest a mechanism proceeding via nucleophilic attack of a dicoordinate borylene intermediate on the aryl ring and subsequent intramolecular B-B bond formation.
In this research, an attempt to create a knowledge-based learning system for the Quranic text has been performed. The knowledge base is made up of the Quranic text along with detailed information about each chapter and verse, and some rules. The system offers the possibility to study the Quran through web-based interfaces, implementing novel visualization techniques for browsing, querying, consulting, and testing the acquired knowledge. Additionally the system possesses knowledge acquisition facilities for maintaining the knowledge base.
The analysis presented in this paper applies to experimental situations where observers or objects to be studied, all at stationary positions, are located in environments the optical thickness of which is strongly different. Non-transparent media comprise thin metallic films, packed or fluidised beds, superconductors, the Earth’s crust, and even dark clouds and other cosmological objects. The analysis applies mapping functions that correlate physical events, e, in non-transparent media, with their images, f(e), tentatively located on standard physical time scale. The analysis demonstrates, however, that physical time, in its rigorous sense, does not exist under non-transparency conditions. A proof of this conclusion is attempted in three steps: i) the theorem “there is no time without space and events” is accepted, (ii) images f[e(s,t)] do not constitute a dense, uncountably infinite set, and (iii) sets of images that are not uncountably infinite do not create physical time but only time-like sequences. As a consequence, mapping f[e(s,t)] in non-transparent space does not create physical analogues to the mathematical structure of the ordered, dense half-set R+ of real numbers, and reverse mapping, f-1f[e(s,t)], the mathematical inverse problem, would not allow unique identification and reconstruction of original events from their images. In these cases, causality as well as invariance of physical processes under time reversal, might be violated. An interesting problem is whether temporal cloaking (a time hole) in a transparent medium, as very recently reported in the literature, can be explained by the present analysis. Existence of time holes could perhaps be possible, not in transparent but in non-transparent media, as follows from the sequence of images, f[e(s,t)], that is not uncountably infinite, in contrast to R+. Impacts are expected for understanding physical diffusion-like, radiative transfer processes and stability models to protect superconductors against quenchs. There might be impacts also in relativity, quantum mechanics, nuclear decay, or in systems close to their phase transitions. The analysis is not restricted to objects of laboratory dimensions.
The mechanism of excimer formation: an experimental and theoretical study on the pyrene dimer
(2017)
The understanding of excimer formation in organic materials is of fundamental importance, since excimers profoundly influence their functional performance in applications such as light-harvesting, photovoltaics or organic electronics. We present a joint experimental and theoretical study of the ultrafast dynamics of excimer formation in the pyrene dimer in a supersonic jet, which is the archetype of an excimer forming system. We perform simulations of the nonadiabatic photodynamics in the frame of TDDFT that reveal two distinct excimer formation pathways in the gas-phase dimer. The first pathway involves local excited state relaxation close to the initial Franck–Condon geometry that is characterized by a strong excitation of the stacking coordinate exhibiting damped oscillations with a period of 350 fs that persist for several picoseconds. The second excimer forming pathway involves large amplitude oscillations along the parallel shift coordinate with a period of ≈900 fs that after intramolecular vibrational energy redistribution leads to the formation of a perfectly stacked dimer. The electronic relaxation within the excitonic manifold is mediated by the presence of intermolecular conical intersections formed between fully delocalized excitonic states. Such conical intersections may generally arise in stacked π-conjugated aggregates due to the interplay between the long-range and short-range electronic coupling. The simulations are supported by picosecond photoionization experiments in a supersonic jet that provide a time-constant for the excimer formation of around 6–7 ps, in good agreement with theory. Finally, in order to explore how the crystal environment influences the excimer formation dynamics we perform large scale QM/MM nonadiabatic dynamics simulations on a pyrene crystal in the framework of the long-range corrected tight-binding TDDFT. In contrast to the isolated dimer, the excimer formation in the crystal follows a single reaction pathway in which the initially excited parallel slip motion is strongly damped by the interaction with the surrounding molecules leading to the slow excimer stabilization on a picosecond time scale.