Download or read book Ultrafast Photophysics of Transition Metal Coordination Complexes Studied with Femtosecond Extreme Ultraviolet Transient Absorption Spectroscopy written by Elizabeth S. Ryland and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Charge Carrier Dynamics in Transition Metal Oxides Studied by Femtosecond Transient Extreme Ultraviolet Absorption Spectroscopy written by Chang-Ming Jiang and published by . This book was released on 2015 with total page 176 pages. Available in PDF, EPUB and Kindle. Book excerpt: With the ability to disentangle electronic transitions that occur on different elements and local electronic structures, time-resolved extreme ultraviolet (XUV) spectroscopy has emerged as a powerful tool for studying ultrafast dynamics in condensed phase systems. In this dissertation, a visible-pump/XUV-probe transient absorption apparatus with femtosecond resolution was constructed to investigate the carrier relaxation dynamics in semiconductors after photo-excitation. This includes timescales for carrier thermalization by carrier-carrier and carrier-phonon scattering. The 30 - 72 eV photon energy coverage (17 - 40 nm wavelength) generated by a table-top XUV light source is suitable for probing the 3p-to-3d core level absorptions of various transition metal oxides (TMOs) with specificities to elements and oxidation states. In Chapter 1, a brief introduction to charge carrier dynamics in semiconductor-based materials is given. In addition, fundamentals of core-level spectroscopy and the high harmonic generation (HHG) process are also addressed in this introductory chapter. Specifications of the experimental apparatus that was constructed are summarized in Chapter 2, including the design concepts and characterization of performance. Chapter 3 presents the spectral tunability of the XUV pulses generated from a semi-infinite gas cell (SIGC), as well as the data acquisition procedures. Charge carrier relaxation dynamics in Co3O4 following the charge transfer excitation pathway at 400 nm are documented in Chapter 4. In Chapter 5, various visible pump wavelengths are used to excite Co3O4 and the differences in the carrier dynamics versus excitation wavelength are considered. After selectively photoexciting a Si/TiO2 heterojunction, the resulted electron transfer process is observed and reported in Chapter 6. The concluding remarks of the dissertation are made in Chapter 7, while several ongoing time-resolved experiments are addressed in the Appendix sections.
Download or read book Ultrafast Photophysical and Photochemical Dynamics of Polyhalogenated Alkanes Cycloalkanes and Transition Metal Complexes written by Darya S Budkina and published by . This book was released on 2019 with total page 230 pages. Available in PDF, EPUB and Kindle. Book excerpt: This work aims at deeper understanding of chemical reaction dynamics, ultrafast photochemical and photophysical relaxation pathways, and energy redistribution and dissipation in the liquid phase on a femto-to-picosecond timescale. Breaking and making of chemical bonds, structural reorganization, and energy flow are all the essence of chemistry, and all occur on the time scale of molecular vibrations (tens of femtoseconds). Important insights about the structure of evolving molecules, relaxation phenomena, and ultrafast photochemical and photophysical population dynamics can be obtained using sub-50-fs time-resolved transient absorption spectroscopy. As a result, highly viable and/or unique information about the mechanism of relaxation dynamics and the nature of short-lived intermediates can be gained. Furthermore, ultrashort laser pulses with duration of 100 fs or shorter can help set up and detect coherent motion in vibronic excited and ground states. Coherence observed in product states provides the knowledge about electronic and nuclear motion along the relaxation path. This yields the information about the potential energy surfaces involved in the photochemical or photophysical process that occurs. The knowledge acquired from such experiments can be used as an entry point for control of femtochemical processes in solution. The technical aspect of this work focuses on developing and optimizing the ultrafast transient absorption setup for studying ultra-rapid photochemical relaxation dynamics in the molecules of interest, namely, geminal dibromocycloalkanes and halogen-containing transition metal complexes. Excitation pulses from deep-UV to near-IR were temporally compressed using prisms compressors to generate sub-40 fs laser pulses. Also, stable white-light continuum pulses used for probing were generated in the wide spectral range of 280 - 760 nm. This thesis is divided into two main parts. The first part provides information about ultrafast dynamics (10-fs time resolution after deconvolution) of geminal dibromocycloalkanes. The second part covers ultrafast radiationless relaxation dynamics of halogen-containing transition metal complexes (IrBr62-, IrCl62-, etc.). A particular focus in this part is on excitation into several vibronic states of the different nature (ligand-to-metal charge-transfer (LMCT) and intraconfigurational), where the lowest-excited intraconfigurational state is accessed via direct femtosecond near-IR (2000 nm) excitation.
Download or read book Ultrafast Transient Absorption Spectroscopy of Valley Carrier Dynamics in Atomically Thin Transition Metal Dichalcogenides written by Cong Mai and published by . This book was released on 2018 with total page 107 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Attosecond Transient Absorption of Solid State and Phase Change Materials written by Marieke Faye Jager and published by . This book was released on 2017 with total page 109 pages. Available in PDF, EPUB and Kindle. Book excerpt: Attosecond science, utilizing short bursts of extreme ultraviolet light, has opened up a fascinating new field of ultafast light-matter interactions, where dynamics in atomic, molecular, and solid state systems can now be followed on the timescale of electron motion. In this dissertation, applications of attosecond pulses toward performing transient absorption spectroscopy experiments on complex electron-correlation-driven processes in material systems are described. In the first chapter, a brief overview of ultrafast spectroscopy, attosecond pulse production, and light-matter interaction in the extreme ultraviolet is provided, which offers the necessary breadth and background for the detailed case study that follows, on the insulator-to-metal phase transition in vanadium dioxide. The origin of the bandgap in vanadium dioxide, which is not predicted to exist under conventional single-particle band theories, has been explained as the result of either electron correlation or structural distortion. The goal of the experiments presented herein is to use transient absorption spectroscopy with attosecond pulses to characterize the timescale of this process and gain a mechanistic understanding of how it occurs. Because vanadium dioxide is heat sensitive, an apparatus had to be specifically tailored to this type of experiments, and it is described in the second chapter. The results and analysis, including extreme ultraviolet static and time-resolved measurements on both the insulating and metallic phases, are described in the third chapter. The second half of this dissertation describes the design and construction of a new vacuum endstation to perform attosecond-pump attosecond-probe measurements, which was constructed and tested at Berkeley and installed at a high power attosecond beamline at the University of Central Florida. Ray tracing simulation and design considerations for the optical layout are described in the fourth chapter, and design of the vacuum endstation, diagnostics, and preliminary experiments and testing can be found in the fifth chapter.
Download or read book Insights Into the Photophysical Reaction Coordinate of 1st Row Transition Metal Chromophores from Vibrational Coherences written by Bryan Christopher Paulus and published by . This book was released on 2020 with total page 277 pages. Available in PDF, EPUB and Kindle. Book excerpt: Controlling the processes which occur following absorption of photon is beneficial for any conceivable application which seeks to convert light into chemical potential. Transition metal chromophores often undergo ultrafast photoinduced transformations which involve significant nuclear motion. This intricate relationship between electronic and nuclear degrees of freedom suggests significant mixing of their wavefunctions and an interdependence of these molecular properties that can map onto the photophysical dynamics. In systems such as these, the rich dynamical information encoded in vibrational coherences can in principle provide unique insight into the nature of this coupling. Furthermore, this has the potential to provide subtle clues for how one could exert some degree of kinetic control through informed structural, compositional, and environmental modifications. This dissertation describes efforts to use excited state vibrational coherences to glean mechanistic information about ultrafast excited state decay in several first-row transition metal chromophore systems and, further, to exploit that information to reengineer the chromophore to alter the photophysical properties.This dissertation begins by using ultrafast transient absorption measurements to provide an updated kinetic model for a series of chromium(III) tris-betadiketonate compounds. Following prompt 4T2 → 2E ISC to the lowest energy excited state, thermally activated back-intersystem crossing repopulates the 4T2 state which internally converts to the ground state on the ~ 1 ps timescale. Steric bulk in the periphery of the molecule reduces the rate of internal conversion resulting in significantly different spectral evolution. Identical low frequency symmetric breathing modes with dephasing times ranging from ~200-2500 fs were identified in the 2E excited state of each molecule. The more rapid dephasing times are likely due to IVR. Similar methodology was then used to characterize the excited state dynamics in a structurally related series of cobalt(III) tris-betadiketonate compounds. Following ligand field excitation into the 1T1g state, each compound had essentially identical biphasic kinetics with ground state recovery occurring with a ~2 ps time constant from an excited state of (t2g)5(eg*) electron configuration. Low frequency metal-ligand breathing modes similar to those observed in the chromium systems were observed with dephasing times consistently on the order of ~200 fs.Finally, two methods to elongate MLCT lifetimes of iron(II) polypyridyl compounds were demonstrated. In the first, the vibrational modes which drive the ultrafast, sub-200 fs MLCT deactivation to the lower energy metal-centered excited states in a [Fe(cage)]2+ control molecule were identified by their coherent oscillations in a transient absorption experiment. These modes were subsequently hindered by incorporation of electronically benign copper(I) atoms to the N4 coordination environments in the periphery of the ligand scaffold resulting in a > 20-fold increase in the MLCT lifetime. In the final study, it was shown that the excited state properties of iron(II) polypyridyl type systems can be systematically and dramatically tuned by swapping out a single bidentate phenanthroline ligand of a [Fe(phen)3]2+ control molecule with stronger-field cyanide or acyclic dicarbene ligands. This modular approach to tuning the kinetics resulted in a > 25-fold increase in the MLCT lifetime and a fundamentally different decay pathway.
Download or read book Watching Electrons Move in Metal Oxide Catalysts written by Somnath Biswas and published by . This book was released on 2020 with total page 170 pages. Available in PDF, EPUB and Kindle. Book excerpt: One of the most important steps in solar energy conversion process is to understand the interfacial charge separation. I have investigated interfacial charge transfer between Fe2O3 and NiO, two earth-abundant semiconductors. This study provides a first direct observation of exciton dissociation and charge separation. The details of this study had been described in Chapter 5.
Download or read book The Photophysics of Pyridinium Betaines Studied by Ultrafast Transient Absorption Spectroscopy written by Zuzanna Pawlowska and published by . This book was released on 2011 with total page 227 pages. Available in PDF, EPUB and Kindle. Book excerpt: This work deals with the photophysics, in solution, of Pyridinium betaine, 2-Pyridin-1-yl-1H-benzimidazole (SBPa), and two derivatives substituted by mono- or bi-thiophene groups. It is based on a combination of steady-state and time-resolved absorption spectroscopic measurements, supported by PCM-(TD)DFT calculations. SBPa was found to undergo ultrafast intramolecular charge transfer (ICT) upon light excitation, with a drastic change in dipole moment. Stationary absorption and emission as well as TDDFT results revealed a strongly solvatochromic CT absorption due to a S0→S2(CT) transition and a non-solvatochromic emission due to S1→S0 transition. Comprehensive band shape analysis and innovative solvatochromic data treatment considering protic and aprotic solvents separately led to a detailed knowledge of the solvent effects and allowed estimating four relevant dipole moments. From extensive femtosecond transient absorption experiments, the overall photophysics of SBPa could be discussed in terms of two distinct CT states and a complete photophysical scheme was proposed: a subpicosecond ICT process occurs from the initially populated S2(CT) state to a charge transfer S1(CT) state, in parallel to the ultrafast production (t
Download or read book X Ray Absorption and X Ray Emission Spectroscopy written by Jeroen A. van Bokhoven and published by John Wiley & Sons. This book was released on 2016-03-21 with total page 940 pages. Available in PDF, EPUB and Kindle. Book excerpt: During the last two decades, remarkable and often spectacular progress has been made in the methodological and instrumental aspects of x–ray absorption and emission spectroscopy. This progress includes considerable technological improvements in the design and production of detectors especially with the development and expansion of large-scale synchrotron reactors All this has resulted in improved analytical performance and new applications, as well as in the perspective of a dramatic enhancement in the potential of x–ray based analysis techniques for the near future. This comprehensive two-volume treatise features articles that explain the phenomena and describe examples of X–ray absorption and emission applications in several fields, including chemistry, biochemistry, catalysis, amorphous and liquid systems, synchrotron radiation, and surface phenomena. Contributors explain the underlying theory, how to set up X–ray absorption experiments, and how to analyze the details of the resulting spectra. X-Ray Absorption and X-ray Emission Spectroscopy: Theory and Applications: Combines the theory, instrumentation and applications of x-ray absorption and emission spectroscopies which offer unique diagnostics to study almost any object in the Universe. Is the go-to reference book in the subject for all researchers across multi-disciplines since intense beams from modern sources have revolutionized x-ray science in recent years Is relevant to students, postdocurates and researchers working on x-rays and related synchrotron sources and applications in materials, physics, medicine, environment/geology, and biomedical materials
Download or read book Chemistry in Action Making Molecular Movies with Ultrafast Electron Diffraction and Data Science written by Lai Chung Liu and published by Springer Nature. This book was released on 2020-09-10 with total page 249 pages. Available in PDF, EPUB and Kindle. Book excerpt: The thesis provides the necessary experimental and analytical tools to unambiguously observe the atomically resolved chemical reactions. A great challenge of modern science has been to directly observe atomic motions during structural transitions, and while this was first achieved through a major advance in electron source brightness, the information content was still limited and new methods for image reconstruction using femtosecond electron diffraction methods were needed. One particular challenge lay in reconciling the innumerable possible nuclear configurations with the observation of chemical reaction mechanisms that reproducibly give the same kind of chemistry for large classes of molecules. The author shows that there is a simple solution that occurs during barrier crossing in which the highly anharmonic potential at that point in nuclear rearrangements couples high- and low-frequency vibrational modes to give highly localized nuclear motions, reducing hundreds of potential degrees of freedom to just a few key modes. Specific examples are given in this thesis, including two photoinduced phase transitions in an organic system, a ring closure reaction, and two direct observations of nuclear reorganization driven by spin transitions. The emerging field of structural dynamics promises to change the way we think about the physics of chemistry and this thesis provides tools to make it happen.
Download or read book 4D Electron Microscopy written by Ahmed H. Zewail and published by World Scientific. This book was released on 2010 with total page 359 pages. Available in PDF, EPUB and Kindle. Book excerpt: Structural phase transitions, mechanical deformations, and the embryonic stages of melting and crystallization are examples of phenomena that can now be imaged in unprecedented structural detail with high spatial resolution, and ten orders of magnitude as fast as hitherto. No monograph in existence attempts to cover the revolutionary dimensions that EM in its various modes of operation nowadays makes possible. The authors of this book chart these developments, and also compare the merits of coherent electron waves with those of synchrotron radiation. They judge it prudent to recall some important basic procedural and theoretical aspects of imaging and diffraction so that the reader may better comprehend the significance of the new vistas and applications now afoot. This book is not a vade mecum - numerous other texts are available for the practitioner for that purpose.
Download or read book The Chemical Bond written by Ahmed Zewail and published by Elsevier. This book was released on 1992-05-14 with total page 333 pages. Available in PDF, EPUB and Kindle. Book excerpt: This inspired book by some of the most influential scientists of our time--including six Nobel laureates--chronicles our emerging understanding of the chemical bond through the last nine decades and into the future. From Pauling's early structural work using x-ray and electron diffraction to Zewail's femtosecond lasers that probe molecular dynamics in real time; from Crick's molecular biology to Rich's molecular recognition, this book explores a rich tradition of scientific heritage and accomplishment. The perspectives given by Pauling, Perutz, Rich, Crick, Porter, Polanyi, Herschbach, Zewail, and Bernstein celebrate major scientific achievements in chemistry and biology with the chemical bond playing a fundamental role. In a unique presentation that also provides some lively insights into the very nature of scientific thought and discovery, The Chemical Bond: Structure and Dynamics will be of general interest to scientists, science historians, and the scientifically inclined populous.
Download or read book Spectroscopy for Materials Characterization written by Simonpietro Agnello and published by John Wiley & Sons. This book was released on 2021-09-08 with total page 500 pages. Available in PDF, EPUB and Kindle. Book excerpt: SPECTROSCOPY FOR MATERIALS CHARACTERIZATION Learn foundational and advanced spectroscopy techniques from leading researchers in physics, chemistry, surface science, and nanoscience In Spectroscopy for Materials Characterization, accomplished researcher Simonpietro Agnello delivers a practical and accessible compilation of various spectroscopy techniques taught and used to today. The book offers a wide-ranging approach taught by leading researchers working in physics, chemistry, surface science, and nanoscience. It is ideal for both new students and advanced researchers studying and working with spectroscopy. Topics such as confocal and two photon spectroscopy, as well as infrared absorption and Raman and micro-Raman spectroscopy, are discussed, as are thermally stimulated luminescence and spectroscopic studies of radiation effects on optical materials. Each chapter includes a basic introduction to the theory necessary to understand a specific technique, details about the characteristic instrumental features and apparatuses used, including tips for the appropriate arrangement of a typical experiment, and a reproducible case study that shows the discussed techniques used in a real laboratory. Readers will benefit from the inclusion of: Complete and practical case studies at the conclusion of each chapter to highlight the concepts and techniques discussed in the material Citations of additional resources ideal for further study A thorough introduction to the basic aspects of radiation matter interaction in the visible-ultraviolet range and the fundamentals of absorption and emission A rigorous exploration of time resolved spectroscopy at the nanosecond and femtosecond intervals Perfect for Master and Ph.D. students and researchers in physics, chemistry, engineering, and biology, Spectroscopy for Materials Characterization will also earn a place in the libraries of materials science researchers and students seeking a one-stop reference to basic and advanced spectroscopy techniques.
Download or read book Concepts and Methods of 2D Infrared Spectroscopy written by Peter Hamm and published by Cambridge University Press. This book was released on 2011-02-24 with total page 297 pages. Available in PDF, EPUB and Kindle. Book excerpt: 2D infrared (IR) spectroscopy is a cutting-edge technique, with applications in subjects as diverse as the energy sciences, biophysics and physical chemistry. This book introduces the essential concepts of 2D IR spectroscopy step-by-step to build an intuitive and in-depth understanding of the method. This unique book introduces the mathematical formalism in a simple manner, examines the design considerations for implementing the methods in the laboratory, and contains working computer code to simulate 2D IR spectra and exercises to illustrate involved concepts. Readers will learn how to accurately interpret 2D IR spectra, design their own spectrometer and invent their own pulse sequences. It is an excellent starting point for graduate students and researchers new to this exciting field. Computer codes and answers to the exercises can be downloaded from the authors' website, available at www.cambridge.org/9781107000056.
Download or read book Applied Photochemistry written by Rachel C. Evans and published by Springer Science & Business Media. This book was released on 2014-07-08 with total page 619 pages. Available in PDF, EPUB and Kindle. Book excerpt: Applied Photochemistry encompasses the major applications of the chemical effects resulting from light absorption by atoms and molecules in chemistry, physics, medicine and engineering, and contains contributions from specialists in these key areas. Particular emphasis is placed both on how photochemistry contributes to these disciplines and on what the current developments are. The book starts with a general description of the interaction between light and matter, which provides the general background to photochemistry for non-specialists. The following chapters develop the general synthetic and mechanistic aspects of photochemistry as applied to both organic and inorganic materials, together with types of materials which are useful as light absorbers, emitters, sensitisers, etc. for a wide variety of applications. A detailed discussion is presented on the photochemical processes occurring in the Earth’s atmosphere, including discussion of important current aspects such as ozone depletion. Two important distinct, but interconnected, applications of photochemistry are in photocatalytic treatment of wastes and in solar energy conversion. Semiconductor photochemistry plays an important role in these and is discussed with reference to both of these areas. Free radicals and reactive oxygen species are of major importance in many chemical, biological and medical applications of photochemistry, and are discussed in depth. The following chapters discuss the relevance of using light in medicine, both with various types of phototherapy and in medical diagnostics. The development of optical sensors and probes is closely related to diagnostics, but is also relevant to many other applications, and is discussed separately. Important aspects of applied photochemistry in electronics and imaging, through processes such as photolithography, are discussed and it is shown how this is allowing the increasing miniaturisation of semiconductor devices for a wide variety of electronics applications and the development of nanometer scale devices. The final two chapters provide the basic ideas necessary to set up a photochemical laboratory and to characterise excited states. This book is aimed at those in science, engineering and medicine who are interested in applying photochemistry in a broad spectrum of areas. Each chapter has the basic theories and methods for its particular applications and directs the reader to the current, important literature in the field, making Applied Photochemistry suitable for both the novice and the experienced photochemist.
Download or read book Luminescent and Photoactive Transition Metal Complexes as Biomolecular Probes and Cellular Reagents written by Kenneth Kam-Wing Lo and published by Springer. This book was released on 2015-06-30 with total page 266 pages. Available in PDF, EPUB and Kindle. Book excerpt: The series Structure and Bonding publishes critical reviews on topics of research concerned with chemical structure and bonding. The scope of the series spans the entire Periodic Table and addresses structure and bonding issues associated with all of the elements. It also focuses attention on new and developing areas of modern structural and theoretical chemistry such as nanostructures, molecular electronics, designed molecular solids, surfaces, metal clusters and supramolecular structures. Physical and spectroscopic techniques used to determine, examine and model structures fall within the purview of Structure and Bonding to the extent that the focus is on the scientific results obtained and not on specialist information concerning the techniques themselves. Issues associated with the development of bonding models and generalizations that illuminate the reactivity pathways and rates of chemical processes are also relevant. The individual volumes in the series are thematic. The goal of each volume is to give the reader, whether at a university or in industry, a comprehensive overview of an area where new insights are emerging that are of interest to a larger scientific audience. Thus each review within the volume critically surveys one aspect of that topic and places it within the context of the volume as a whole. The most significant developments of the last 5 to 10 years should be presented using selected examples to illustrate the principles discussed. A description of the physical basis of the experimental techniques that have been used to provide the primary data may also be appropriate, if it has not been covered in detail elsewhere. The coverage need not be exhaustive in data, but should rather be conceptual, concentrating on the new principles being developed that will allow the reader, who is not a specialist in the area covered, to understand the data presented. Discussion of possible future research directions in the area is welcomed. Review articles for the individual volumes are invited by the volume editors. Readership: research scientists at universities or in industry, graduate students Special offer For all customers who have a standing order to the print version of Structure and Bonding, we offer free access to the electronic volumes of the Series published in the current year via SpringerLink.
Download or read book Spin Crossover Materials written by Malcolm A. Halcrow and published by John Wiley & Sons. This book was released on 2013-01-07 with total page 729 pages. Available in PDF, EPUB and Kindle. Book excerpt: The phenomenon of spin-crossover has a large impact on the physical properties of a solid material, including its colour, magnetic moment, and electrical resistance. Some materials also show a structural phase change during the transition. Several practical applications of spin-crossover materials have been demonstrated including display and memory devices, electrical and electroluminescent devices, and MRI contrast agents. Switchable liquid crystals, nanoparticles, and thin films of spin-crossover materials have also been achieved. Spin-Crossover Materials: Properties and Applications presents a comprehensivesurvey of recent developments in spin-crossover research, highlighting the multidisciplinary nature of this rapidly expanding field. Following an introductory chapter which describes the spin-crossover phenomenon and historical development of the field, the book goes on to cover a wide range of topics including Spin-crossover in mononuclear, polynuclear and polymeric complexes Structure: function relationships in molecular spin-crossover materials Charge-transfer-induced spin-transitions Reversible spin-pairing in crystalline organic radicals Spin-state switching in solution Spin-crossover compounds in multifunctional switchable materials and nanotechnology Physical and theoretical methods for studying spin-crossover materials Spin-Crossover Materials: Properties and Applications is a valuable resource for academic researchers working in the field of spin-crossover materials and topics related to crystal engineering, solid state chemistry and physics, and molecular materials. Postgraduate students will also find this book useful as a comprehensive introduction to the field.
