Read by QxMD icon Read


Rundong Zhao, Yanoar Pribadi Sarwono, Rui-Qin Zhang
The tunneling lifetime of an electron escaping from an atom is calculated using a projected Green's function method, combining with the radial potential of the atom which is obtained from density functional theory. Results of the calculated electron tunneling lifetimes in model systems such as a quantum dot are shown to be comparable with other theoretical studies. For the first time, we have obtained the tunneling lifetimes of electrons escaping from a series of atoms (He, Ne, Ar, Kr, H, Li, Na, K) under a static electric field...
August 14, 2017: Journal of Chemical Physics
Jakob Petersen, Eli Pollak
Attosecond ionization experiments have not resolved the question: ``What is the tunneling time?''. Different definitions of tunneling time lead to different results.Secondly, a zero tunneling time for a material particle suggests that the non-relativistic theory includes speeds greater than the speed of light. Chemical reactions, occurring via tunneling, should then not be considered in terms of a non-relativistic quantum theory calling into question quantum dynamics computations on tunneling reactions. To answer these questions, we define a new experimentally measurable paradigm - the tunneling flight time - and show that it vanishes for scattering through an Eckart or a square barrier, irrespective of barrier length or height, generalizing the Hartman effect...
August 9, 2017: Journal of Physical Chemistry Letters
Ryoji Anzaki, Takeshi Sato, Kenichi L Ishikawa
We present a fully general time-dependent multiconfiguration self-consistent-field method to describe the dynamics of a system consisting of arbitrarily different kinds and numbers of interacting fermions and bosons. The total wave function is expressed as a superposition of different configurations constructed from time-dependent spin-orbitals prepared for each particle kind. We derive equations of motion followed by configuration-interaction (CI) coefficients and spin-orbitals for general, not restricted to full-CI, configuration spaces...
August 9, 2017: Physical Chemistry Chemical Physics: PCCP
Adam Bruner, Samuel Hernandez, Francois Mauger, Paul M Abanador, Daniel LaMaster, Mette B Gaarde, Kenneth J Schafer, Kenneth Lopata
We investigate the ability of time-dependent density functional theory (TDDFT) to capture attosecond valence electron dynamics resulting from sudden X-ray ionization of a core electron. In this special case, the initial state can be constructed unambiguously, and issues with resonant excitation can be bypassed, allowing for a simple test of the accuracy of the dynamics. The response following nitrogen K-edge ionization in nitrosobenzene shows excellent agreement with fourth-order algebraic diagrammatic construction (ADC(4)) results, suggesting that a properly chosen initial state allows TDDFT to adequately capture charge migration...
August 9, 2017: Journal of Physical Chemistry Letters
Pengfei Lan, Marc Ruhmann, Lixin He, Chunyang Zhai, Feng Wang, Xiaosong Zhu, Qingbin Zhang, Yueming Zhou, Min Li, Manfred Lein, Peixiang Lu
We report attosecond-scale probing of the laser-induced dynamics in molecules. We apply the method of high-harmonic spectroscopy, where laser-driven recolliding electrons on various trajectories record the motion of their parent ion. Based on the transient phase-matching mechanism of high-order harmonic generation, short and long trajectories contributing to the same harmonic order are distinguishable in both the spatial and frequency domains, giving rise to a one-to-one map between time and photon energy for each trajectory...
July 21, 2017: Physical Review Letters
Jie Li, Xiaoming Ren, Yanchun Yin, Kun Zhao, Andrew Chew, Yan Cheng, Eric Cunningham, Yang Wang, Shuyuan Hu, Yi Wu, Michael Chini, Zenghu Chang
The motion of electrons in the microcosm occurs on a time scale set by the atomic unit of time-24 attoseconds. Attosecond pulses at photon energies corresponding to the fundamental absorption edges of matter, which lie in the soft X-ray regime above 200 eV, permit the probing of electronic excitation, chemical state, and atomic structure. Here we demonstrate a soft X-ray pulse duration of 53 as and single pulse streaking reaching the carbon K-absorption edge (284 eV) by utilizing intense two-cycle driving pulses near 1...
August 4, 2017: Nature Communications
Oshrat Tchulov, Matteo Negro, Salvatore Stagira, Michele Devetta, Caterina Vozzi, Eugene Frumker
We introduce a novel in-situ strong field ionization tomography approach for characterizing the spatial density distribution of gas jets. We show that for typical intensities in high harmonic generation experiments, the strong field ionization mechanism used in our approach provides an improvement in the resolution close to factor of 2 (resolving about 8 times smaller voxel volume), when compared to linear/single-photon imaging modalities. We find, that while the depth of scan in linear tomography is limited by resolution loss due to the divergence of the driving laser beam, in the proposed approach the depth of focus is localized due to the inherent physical nature of strong-field interaction and discuss implications of these findings...
July 31, 2017: Scientific Reports
Nicolas Camus, Enderalp Yakaboylu, Lutz Fechner, Michael Klaiber, Martin Laux, Yonghao Mi, Karen Z Hatsagortsyan, Thomas Pfeifer, Christoph H Keitel, Robert Moshammer
The first hundred attoseconds of the electron dynamics during strong field tunneling ionization are investigated. We quantify theoretically how the electron's classical trajectories in the continuum emerge from the tunneling process and test the results with those achieved in parallel from attoclock measurements. An especially high sensitivity on the tunneling barrier is accomplished here by comparing the momentum distributions of two atomic species of slightly deviating atomic potentials (argon and krypton) being ionized under absolutely identical conditions with near-infrared laser pulses (1300 nm)...
July 14, 2017: Physical Review Letters
Tahir Shaaran, Rana Nicolas, Bianca Iwan, Milutin Kovacev, Hamed Merdji
Nano-structures excited by light can enhance locally the electric field when tuned to plasmonic resonances. This phenomenon can be used to boost non-linear processes such as harmonic generation in crystals or in gases, Raman excitation, and four wave mixing. Here we present a theoretical investigation of the near-field phase matching of attosecond pulses emitted by high-order harmonic generation (HHG) of an atom immersed in a multi-cycle femtosecond infrared laser field and a spatially inhomogeneous plasmonic field...
July 25, 2017: Scientific Reports
Xiaojing Wu, Jean-Marie Teuler, Fabien Cailliez, Carine Clavaguéra, Dennis R Salahub, Aurélien de la Lande
We propose a methodology for simulating attosecond electron dynamics in large molecular systems. Our approach is based on the combination of real time time-dependent-density-functional theory (RT-TDDFT) and polarizable Molecular Mechanics (MMpol) with the point-charge-dipole model of electrostatic induction. We implemented this methodology in the software deMon2k that relies heavily on auxiliary fitted densities. In the context of RT-TDDFT/MMpol simulations, fitted densities allow the cost of the calculations to be reduced drastically on three fronts: (i) the Kohn-Sham potential, (ii) the electric field created by the (fluctuating) electron cloud which is needed in the QM/MM interaction, and (iii) the analysis of the fluctuating electron density on-the-fly...
August 17, 2017: Journal of Chemical Theory and Computation
Murat Sivis, Marco Taucer, Giulio Vampa, Kyle Johnston, André Staudte, Andrei Yu Naumov, D M Villeneuve, Claus Ropers, P B Corkum
The advent of high-harmonic generation in gases 30 years ago set the foundation for attosecond science and facilitated ultrafast spectroscopy in atoms, molecules, and solids. We explore high-harmonic generation in the solid state by means of nanostructured and ion-implanted semiconductors. We use wavelength-selective microscopic imaging to map enhanced harmonic emission and show that the generation medium and the driving field can be locally tailored in solids by modifying the chemical composition and morphology...
July 21, 2017: Science
M A Fareed, V V Strelkov, N Thiré, S Mondal, B E Schmidt, F Légaré, T Ozaki
In high-order harmonic generation, resonant harmonics (RH) are sources of intense, coherent extreme-ultraviolet radiation. However, intensity enhancement of RH only occurs for a single harmonic order, making it challenging to generate short attosecond pulses. Moreover, the mechanism involved behind such RH was circumstantial, because of the lack of direct experimental proofs. Here, we demonstrate the exact quantum paths that electron follows for RH generation using tin, showing that it involves not only the autoionizing state, but also a harmonic generation from dressed-AIS that appears as two coherent satellite harmonics at frequencies ±2Ω from the RH (Ω represents laser frequency)...
July 17, 2017: Nature Communications
F X Kärtner, F Ahr, A-L Calendron, H Çankaya, S Carbajo, G Chang, G Cirmi, K Dörner, U Dorda, A Fallahi, A Hartin, M Hemmer, R Hobbs, Y Hua, W R Huang, R Letrun, N Matlis, V Mazalova, O D Mücke, E Nanni, W Putnam, K Ravi, F Reichert, I Sarrou, X Wu, A Yahaghi, H Ye, L Zapata, D Zhang, C Zhou, R J D Miller, K K Berggren, H Graafsma, A Meents, R W Assmann, H N Chapman, P Fromme
X-ray crystallography is one of the main methods to determine atomic-resolution 3D images of the whole spectrum of molecules ranging from small inorganic clusters to large protein complexes consisting of hundred-thousands of atoms that constitute the macromolecular machinery of life. Life is not static, and unravelling the structure and dynamics of the most important reactions in chemistry and biology is essential to uncover their mechanism. Many of these reactions, including photosynthesis which drives our biosphere, are light induced and occur on ultrafast timescales...
September 1, 2016: Nuclear Instruments & Methods in Physics Research. Section A, Accelerators, Spectrometers, Detectors and Associated Equipment
D E Rivas, A Borot, D E Cardenas, G Marcus, X Gu, D Herrmann, J Xu, J Tan, D Kormin, G Ma, W Dallari, G D Tsakiris, I B Földes, S-W Chou, M Weidman, B Bergues, T Wittmann, H Schröder, P Tzallas, D Charalambidis, O Razskazovskaya, V Pervak, F Krausz, L Veisz
The observation and manipulation of electron dynamics in matter call for attosecond light pulses, routinely available from high-order harmonic generation driven by few-femtosecond lasers. However, the energy limitation of these lasers supports only weak sources and correspondingly linear attosecond studies. Here we report on an optical parametric synthesizer designed for nonlinear attosecond optics and relativistic laser-plasma physics. This synthesizer uniquely combines ultra-relativistic focused intensities of about 10(20) W/cm(2) with a pulse duration of sub-two carrier-wave cycles...
July 12, 2017: Scientific Reports
E P Månsson, S De Camillis, M C Castrovilli, M Galli, M Nisoli, F Calegari, J B Greenwood
Understanding how energetic charged particles damage DNA is crucial for improving radiotherapy techniques such as hadron therapy and for the development of new radiosensitizer drugs. In the present study, the damage caused by energetic particles was simulated by measuring the action of extreme ultraviolet (XUV) attosecond pulses on the DNA building blocks thymine and thymidine. This allowed the ultrafast processes triggered by direct ionization to be probed with an optical pulse with a time resolution of a few femtoseconds...
June 28, 2017: Physical Chemistry Chemical Physics: PCCP
Samuel G Walt, Niraghatam Bhargava Ram, Marcos Atala, Nikolay I Shvetsov-Shilovski, Aaron von Conta, Denitsa Baykusheva, Manfred Lein, Hans Jakob Wörner
Strong-field photoelectron holography and laser-induced electron diffraction (LIED) are two powerful emerging methods for probing the ultrafast dynamics of molecules. However, both of them have remained restricted to static systems and to nuclear dynamics induced by strong-field ionization. Here we extend these promising methods to image purely electronic valence-shell dynamics in molecules using photoelectron holography. In the same experiment, we use LIED and photoelectron holography simultaneously, to observe coupled electronic-rotational dynamics taking place on similar timescales...
June 15, 2017: Nature Communications
C-Z Gao, P M Dinh, P-G Reinhard, E Suraud
We study from a theoretical perspective the ionization of molecules and clusters induced by irradiation of a combined two-color laser field consisting of a train of attosecond XUV pulses in the presence of an IR field. We use time-dependent density-functional theory (TDDFT) in real time and real space as a theoretical tool. The calculated results are compared to experimental data when available. We also compare TDDFT with results obtained using a time-dependent Schrödinger equation (TDSE), which is well suited to simple systems while TDDFT allows dealing with more complex molecules and clusters...
June 21, 2017: Physical Chemistry Chemical Physics: PCCP
David Ayuso, Alicia Palacios, Piero Decleva, Fernando Martín
The combination of attosecond pump-probe techniques with mass spectrometry methods has recently led to the first experimental demonstration of ultrafast charge dynamics in a biomolecule, the amino acid phenylalanine [Calegari et al., Science, 2014, 346, 336]. Using an extension of the static-exchange density functional theory (DFT) method, the observed dynamics was explained as resulting from the coherent superposition of ionic states produced by the broadband attosecond pulse. Here, we have used the static-exchange DFT method to investigate charge migration induced by attosecond pulses in the glycine molecule...
June 20, 2017: Physical Chemistry Chemical Physics: PCCP
Cong Chen, Zhensheng Tao, Adra Carr, Piotr Matyba, Tibor Szilvási, Sebastian Emmerich, Martin Piecuch, Mark Keller, Dmitriy Zusin, Steffen Eich, Markus Rollinger, Wenjing You, Stefan Mathias, Uwe Thumm, Manos Mavrikakis, Martin Aeschlimann, Peter M Oppeneer, Henry Kapteyn, Margaret Murnane
Electron-electron interactions are the fastest processes in materials, occurring on femtosecond to attosecond timescales, depending on the electronic band structure of the material and the excitation energy. Such interactions can play a dominant role in light-induced processes such as nano-enhanced plasmonics and catalysis, light harvesting, or phase transitions. However, to date it has not been possible to experimentally distinguish fundamental electron interactions such as scattering and screening. Here, we use sequences of attosecond pulses to directly measure electron-electron interactions in different bands of different materials with both simple and complex Fermi surfaces...
July 3, 2017: Proceedings of the National Academy of Sciences of the United States of America
D M Villeneuve, Paul Hockett, M J J Vrakking, Hiromichi Niikura
Electrons detached from atoms or molecules by photoionization carry information about the quantum state from which they originate, as well as the continuum states into which they are released. Generally, the photoelectron momentum distribution is composed of a coherent sum of angular momentum components, each with an amplitude and phase. Here we show, by using photoionization of neon, that a train of attosecond pulses synchronized with an infrared laser field can be used to disentangle these angular momentum components...
June 16, 2017: Science
Fetch more papers »
Fetching more papers... Fetching...
Read by QxMD. Sign in or create an account to discover new knowledge that matter to you.
Remove bar
Read by QxMD icon Read

Search Tips

Use Boolean operators: AND/OR

diabetic AND foot
diabetes OR diabetic

Exclude a word using the 'minus' sign

Virchow -triad

Use Parentheses

water AND (cup OR glass)

Add an asterisk (*) at end of a word to include word stems

Neuro* will search for Neurology, Neuroscientist, Neurological, and so on

Use quotes to search for an exact phrase

"primary prevention of cancer"
(heart or cardiac or cardio*) AND arrest -"American Heart Association"