Download or read book Ultrafast Dynamics of Electrons at Interfaces written by Jason Douglas McNeill and published by . This book was released on 1999 with total page 382 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Ultrafast Dynamics of Electrons at Interfaces written by and published by . This book was released on 1999 with total page 175 pages. Available in PDF, EPUB and Kindle. Book excerpt: Electronic states of a thin layer of material on a surface possess unique physical and chemical properties. Some of these properties arise from the reduced dimensionality of the thin layer with respect to the bulk or the properties of the electric field where two materials of differing dielectric constants meet at an interface. Other properties are related to the nature of the surface chemical bond. Here, the properties of excess electrons in thin layers of Xenon, Krypton, and alkali metals are investigated, and the bound state energies and effective masses of the excess electrons are determined using two-photon photoemission. For Xenon, the dependence of bound state energy, effective mass, and lifetime on layer thickness from one to nine layers is examined. Not all quantities were measured at each coverage. The two photon photoemission spectra of thin layers of Xenon on a Ag(111) substrate exhibit a number of sharp, well-defined peaks. The binding energy of the excess electronic states of Xenon layers exhibited a pronounced dependence on coverage. A discrete energy shift was observed for each additional atomic layer. At low coverage, a series of states resembling a Rydberg series is observed. This series is similar to the image state series observed on clean metal surfaces. Deviations from image state energies can be described in terms of the dielectric constant of the overlayer material and its effect on the image potential. For thicker layers of Xe (beyond the first few atomic layers), the coverage dependence of the features begins to resemble that of quantum well states. Quantum well states are related to bulk band states. However, the finite thickness of the layer restricts the perpendicular wavevector to a discrete set of values. Therefore, the spectrum of quantum well states contains a series of peaks which correspond to the various allowed values of the perpendicular wavevector. Analysis of the quantum well spectrum yields electronic band structure information. In this case, the quantum well states examined are derived from the Xenon conduction band. Measurements of the energies as a function of coverage yield the dispersion along the axis perpendicular to the surface while angle-resolved two-photon photoemission measurements yield information about dispersion along the surface parallel. The relative importance of the image potential and the overlayer band structure also depends on the quantum number and energy of the state. Some members of the image series may have an energy which is in an energy gap of the layer material, therefore such states may tend to remain physically outside the layer and retain much of their image character even at higher coverages. This is the case for the n = 1 image state of the Xe/Ag(111) system. The energies of image states which are excluded from the layer have a complex dependence on the thickness of the layer and its dielectric constant. The population decay kinetics of excited electronic states of the layer were also determined. Lifetimes are reported for the first three excited states for 1-6 atomic layers of Xe on Ag(111). As the image states evolve into quantum well states with increasing coverage, the lifetimes undergo an oscillation which marks a change in the spatial extent of the state. For example, the n = 2 quantum well state decreases substantially at 3-5 layers as the electron probability density in the layer increases. The lifetime data are modeled by extending the two-band nearly-free-electron approximation to account for the insulating Xe layer.
Download or read book Ultrafast Dynamics In Molecules Nanostructures And Interfaces Selected Lectures Presented At Symposium On Ultrafast Dynamics Of The 7th International Conference On Materials For Advanced Technologies written by Guglielmo Lanzani and published by World Scientific. This book was released on 2014-01-22 with total page 304 pages. Available in PDF, EPUB and Kindle. Book excerpt: Primary events in natural systems or devices occur on extremely short time scales, and yet determine in many cases the final performance or output. For this reason research in ultrafast science is of primary importance and impact in both fundamental research as well as its applications. This book reviews the advances in the field, addressing timely and open questions such as the role of quantum coherence in biology, the role of excess energy in electron injection at photovoltaic interfaces or the dynamics in quantum confined structures (e.g. multi carrier generation). The approach is that of a monograph, with a broad tutorial introduction and an overview of the recent results. This volume includes selected lectures presented at Symposium on Ultrafast Dynamics of the 7th International Conference on Materials for Advanced Technologies.
Download or read book Ultrafast Studies of Electron Dynamics at Metal dielectric Interfaces written by Nien-Hui Ge and published by . This book was released on 1998 with total page 372 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Ultrafast Electron Dynamics at Dielectric metal Interfaces written by Sean Alexander Garrett-Roe and published by . This book was released on 2005 with total page 310 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Ultrafast Dynamics Driven by Intense Light Pulses written by Markus Kitzler and published by Springer. This book was released on 2015-07-24 with total page 385 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book documents the recent vivid developments in the research field of ultrashort intense light pulses for probing and controlling ultrafast dynamics. The recent fascinating results in studying and controlling ultrafast dynamics in ever more complicated systems such as (bio-)molecules and structures of meso- to macroscopic sizes on ever shorter time-scales are presented. The book is written by some of the most eminent experimental and theoretical experts in the field. It covers the new groundbreaking research directions that were opened by the availability of new light sources such as fully controlled intense laser fields with durations down to a single oscillation cycle, short-wavelength laser-driven attosecond pulses and intense X-ray pulses from the upcoming free electron lasers. These light sources allowed the investigation of dynamics in atoms, molecules, clusters, on surfaces and very recently also in nanostructures and solids in new regimes of parameters which, in turn, led to the identification of completely new dynamics and methods for controlling it. Example topics covered by this book include the study of ultrafast processes in large molecules using attosecond pulses, control of ultrafast electron dynamics in solids with shaped femtosecond laser pulses, light-driven ultrafast plasmonic processes on surfaces and in nanostructures as well as research on atomic and molecular systems under intense X-ray radiation. This book is equally helpful for people who would like to step into this field (e.g. young researchers), for whom it provides a broad introduction, as well as for already experienced researchers who may enjoy the exhaustive discussion that covers the research on essentially all currently studied objects and with all available ultrafast pulse sources.
Download or read book Ultrafast Dynamics in Molecules Nanostructures and Interfaces written by G. G. Gurzadian and published by World Scientific Publishing Company Incorporated. This book was released on 2014 with total page 291 pages. Available in PDF, EPUB and Kindle. Book excerpt: Primary events in natural systems or devices occur on extremely short time scales, and yet determine in many cases the final performance or output. For this reason research in ultrafast science is of primary importance and impact in both fundamental research as well as its applications. This book reviews the advances in the field, addressing timely and open questions such as the role of quantum coherence in biology, the role of excess energy in electron injection at photovoltaic interfaces or the dynamics in quantum confined structures (e.g. multi carrier generation). The approach is that of a monograph, with a broad tutorial introduction and an overview of the recent results. This volume includes selected lectures presented at Symposium on Ultrafast Dynamics of the 7th International Conference on Materials for Advanced Technologies.
Download or read book Ultrafast Studies of Electron Dynamics at Metal dielectric Interfaces written by and published by . This book was released on 1998 with total page 184 pages. Available in PDF, EPUB and Kindle. Book excerpt: Femtosecond time- and angle-resolved two-photon photoemission spectroscopy has been used to study fundamental aspects of excited electron dynamics at metal-dielectric interfaces, including layer-by-layer evolution of electronic structure and two-dimensional electron localization. On bare Ag(111), the lifetimes of image states are dominated by their position with respect to the projected bulk band structure. The n = 2 state has a shorter lifetime than the n = 1 state due to degeneracy with the bulk conduction band. As the parallel momentum of the n = 1 image electron increases, the lifetime decreases. With decreasing temperatures, the n = 1 image electrons, with zero or nonzero parallel momentum, all become longer lived. Adsorption of one to three layers of n-heptane results in an approximately exponential increase in lifetime as a function of layer thickness. This results from the formation of a tunneling barrier through which the interfacial electrons must decay, consistent with the repulsive bulk electron affinity of n-alkanes. The lifetimes of the higher quantum states indicate that the presence of the monolayer significantly reduces coupling of the image states to the bulk band structure. These results are compared with predictions of a dielectric continuum model. The study of electron lateral motion shows that optical excitation creates interfacial electrons in quasifree states for motion parallel to the n-heptane/Ag(111) interface. These initially delocalized electrons decay into a localized state within a few hundred femtoseconds. The localized electrons then decay back to the metal by tunneling through the adlayer potential barrier. The localization time depends strongly on the electron's initial parallel momentum and exhibits a non-Arrhenius temperature dependence. The experimental findings are consistent with a 2-D self-trapping process in which electrons become localized by interacting with the topmost plane of the alkane layer. The energy dependence of the self-trapping rate has been modeled with an electron transfer theory. This analysis shows that self-trapping involves inter- and intramolecular vibrational modes of the overlayer and the non-Arrhenius temperature dependence is a result of a strong quantum contribution from the intramolecular modes. These results for a model interface contribute to the fundamental understanding of electron behavior at the interface between metals and molecular solids.
Download or read book Ultrafast Dynamics of Quantum Systems written by Baldassare di Bartolo and published by Springer Science & Business Media. This book was released on 2006-04-11 with total page 721 pages. Available in PDF, EPUB and Kindle. Book excerpt: Based on a NATO Advanced Summer Institute, this volume discusses physical models, mathematical formalisms, experimental techniques, and applications for ultrafast dynamics of quantum systems. These systems are used in laser optics, spectroscopy, and utilize monochromaticity, spectral brightness, coherence, power density, and tunability of laser sources.
Download or read book Ultrafast Spin dependent Electron Dynamics at the Cobalt Alq 3 Interface written by Sabine Steil and published by . This book was released on 2014 with total page 125 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Femtosecond Studies of Electron Dynamics and Structure at Metal molecular Interfaces written by André David Miller and published by . This book was released on 2002 with total page 238 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Ultrafast Phenomena XII written by T. Elsaesser and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 709 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents the latest advances in ultrafast science, including ultrafast laser and measurement technology, and studies of ultrafast phenomena. It summarizes the results presented at the 12th Ultrafast Phenomena Conference and reviews the state of the art of this important and rapidly advancing field.
Download or read book Ultrafast Dynamics of Electrons and Phonons in Graphitic Materials written by and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This work focuses on the ultrafast dynamics of electrons and phonons in graphitic materials. In particular, we experimentally investigated the factors which influence the transport properties of graphite and carbon nanotubes. In the first part of this dissertation, we used Time-resolved Two Photon photoemission (TR-TPP) spectroscopy to probe the dynamics of optically excited charge carriers above the Fermi energy of double-wall carbon nanotubes (DWNTs). In the second part of this study, time-resolved anti-Stokes Raman (ASR) spectroscopy is applied to investigating in real time the phonon-phonon interactions, and addressing the way the temperature affects the dynamics of single-wall carbon nanotubes (SWNTs) and graphite. With respect to the first part, we aim to deeply understand the dynamics of the charge carriers and electron-phonon interactions, in order to achieve an as complete as possible knowledge of DWNTs. We measured the energy transfer rate from the electronic system to the lattice, and we observed a strong non-linear increase with the temperature of the electrons. In addition, we determined the electron-phonon coupling parameter, and the mean-free path of the electrons. The TR-TPP technique enables us to measure the above quantities without any electrical contacts, with the advantage of reducing the errors introduced by the metallic electrodes. The second investigation uses time-resolved ASR spectroscopy to probe in real time the G-mode non-equilibrium phonon dynamics and the energy relaxation paths towards the lattice by variation of the temperature in SWNTs and graphite. The lifetime range of the optically excited phonons obtained is 1.23 ps to 0.70 ps in the lowest (cryogenic temperatures) and highest temperature limits, respectively. We have also observed an increase in the energy of the G-mode optical phonons in graphite with the transient temperature. The findings of this study are important since the non-equilibrium phonon population has been invoked to explain the negative differential conductance and current saturation in high biased transport phenomena.
Download or read book Ultrafast Electron Dynamics of Ultrathin Films of Electrochemical Solvents Adsorbed on an Ag 111 Substrate written by Matthew Lee Strader and published by . This book was released on 2008 with total page 250 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Dynamics at Solid State Surfaces and Interfaces Volume 1 written by Uwe Bovensiepen and published by John Wiley & Sons. This book was released on 2010-11-29 with total page 631 pages. Available in PDF, EPUB and Kindle. Book excerpt: This two-volume work covers ultrafast structural and electronic dynamics of elementary processes at solid surfaces and interfaces, presenting the current status of photoinduced processes. Providing valuable introductory information for newcomers to this booming field of research, it investigates concepts and experiments, femtosecond and attosecond time-resolved methods, as well as frequency domain techniques. The whole is rounded off by a look at future developments.
Download or read book Excited Electronic States and Ultrafast Dynamic Electron Trapping at Alkali Halide written by David Edward Stuart Suich and published by . This book was released on 2015 with total page 95 pages. Available in PDF, EPUB and Kindle. Book excerpt: Angle- and time-resolved two-photon photoemission is used to study the ultrafast electron dynamics at alkali halide-metal interfaces under ultrahigh vacuum conditions. The initial excited states and electron localization at trap states are characterized on the ultrafast timescales. For NaCl on Ag(100), the well characterized island growth of NaCl on low Miller indices noble metal substrates in the ultrathin coverage limit is studied. The initial excited states observed correspond to the n = 1, n = 2, and n = 3 image potential state (IPS) progression of the NaCl-metal interface. The delocalized n = 1 IPS electrons, evidenced by their light effective mass, m* = 0.7me, are found to localize via population transfer to two localized states on the hundreds of femtosecond timescale. The first localized state, indicated by its flat band dispersion, is located at the bottom of the free state band with a decay lifetime comparable to the free n = 1 electrons of 100 fs. The second, discrete, localized state observed leads to a binding energy gain of hundreds of meVs and results in a substantial lifetime increase of 0.5-1 ps versus the ca. 100 fs of the initial delocalized n = 1 IPS. The long-lived localized state's lifetime shows an exponential dependence with increasing coverage, indicating the NaCl film acts as a tunneling barrier and that the localized state is located at the surface-vacuum interface, versus inside the film. The long lived localized state is assigned to low coordinated defect sites on the NaCl surface such as step edges, corners, and NaCl pair vacancies. The binding energy and decay lifetime of electron trapping at low coordinated defects shows strong temperature dependence but qualitatively similar behavior for temperatures of 125-350 K. A new emerging trap state is observed at the NaCl/Ag(100) upon cooling to temperatures “ 125 K. This state is only observed after long time delays ( 500 fs) and at increased binding energies of 380 meV. Additionally, the emerging trap state shows an even further enhanced lifetime of a few picoseconds. A transition temperature for observing this state is identified as 81 K or 7 meV of thermal energy. Furthermore, the emerging state is shown to arise from electron population transfer from trapped electrons at low coordinated defect sites. In temperatures > 100 K, the lifetime of electrons trapped at low coordinated defect sites decreases as temperature increases due to thermally activated tunneling back to the metal. However, the reverse behavior is observed for the same state for temperatures
Download or read book Ultrafast Electronic and Structural Dynamics written by Kiyoshi Ueda and published by Springer. This book was released on 2024-08-12 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book illustrates advanced technologies for imaging electrons and atoms in action in various forms of matter, from atoms and diatoms to protein molecules and condensed matter. The technologies that are described employ ultrafast pulsed lasers, X-ray free electron lasers, and pulsed electron guns, with pulse durations from femtoseconds, suitable to visualize atoms in action, to attoseconds, needed to visualize ballistic electron motion. Advanced theories, indispensable for understanding such ultrafast imaging and spectroscopy data on electrons and atoms in action, are also described. The book consists of three parts. The first part describes probing methods of attosecond electron dynamics in atoms, molecules, liquids, and solids. The second part describes femtosecond structural dynamics and coupling of structural change and electron motion in molecules and solids The last part is dedicated to ultrafast photophysical processes and chemical reactions of protein molecules responsible for biological functions.
