Download or read book Dynamics of Diatomic Molecules in Intense Laser Fields written by Mathias Uhlmann and published by . This book was released on 2006 with total page 143 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Dynamics of Diatomic Molecules in Intense Laser Fields written by and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A realistic description of ionization in intense laser fields is implemented into the Non-Adiabatic Quantum Molecular Dynamics (NA-QMD) formalism. First, the error of a finite basis expansion is considered and a new measure is proposed for time-dependent calculations. This is used to investigate systematically the influence of the used basis set in calculations on the hydrogen atom in intense laser fields. Second, absorbing boundary conditions in basis expansion are introduced via an imaginary potential into the effective one-particle Hamiltonian. It is shown that the used form of the absorber potential is valid in many-electron time-dependent density functional theory calculations, i.e. that only ionized states are affected by the absorbing potential. The absorber is then tested on reference calculations that exist for H and aligned H+2 in intense laser fields. Excellent agreement is found. Additionally, an approximative treatment of the missing electron-nuclear correlations is proposed. It is found in calculations on H+2 that a qualitative improvement of the description of nuclear dynamics results. The extension of the NA-QMD formalism is then used to investigate the alignment behavior of diatomic molecules. Recent experiments on H+2 and H2 are reviewed and explained. It is found that dynamic alignment, i.e. the laser induced rotation of the molecule, plays a central role. The alignment behavior of H+2 and H2 and its intensity dependence is investigated after that. A drastic difference between H+2 and H2 is found in NA-QMD as well as model calculations. Then, the focus is on an astonishing new effect that has been found in N2 calculations. This effect which is called "rotational destabilization" is studied on the model system H+2. Yet, it might be observable only in heavy dimers and might have already been found in an experiment on I2.

Download or read book Dynamics of Diatomic Molecules in Intense Fields written by Liang-You Peng and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Spectra and Dynamics of Diatomic Molecules written by Helene Lefebvre-Brion and published by Academic Press. This book was released on 2004-04-02 with total page 797 pages. Available in PDF, EPUB and Kindle. Book excerpt: And concluding with some examples of polyatomic molecule dynamics. P Students will discover that there is a fascinating world of cause-and-effect localized dynamics concealed beyond the reduction of spectra to archival molecular constants and the exact ab initio computation of molecular properties.-

Download or read book Nuclear Dynamics and Ionization of Diatomic Molecules in Intense Laser Fields written by Maia Magrakvelidze and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In this work we studied the dynamics of deuterium molecules in intense laser fields both experimentally and theoretically. For studying the dynamics of the molecule on a time scale that is less than the period of the laser field (2.7 fs for 800 nm), an advanced experimental technique: COLTRIMS (cold target recoil ion momentum spectroscopy) was used. COLTRIMS allows studying the nuclear dynamics without using attosecond laser pulses. This thesis consists of two main parts. In the first part we deduced the angular dependence of the ionization probability of the molecule without aligning the molecules, by measuring the relative angle between a deuteron resulting from field dissociation and an emitted electron using electron-ion coincidence measurements with circularly polarized light in COLTRIMS. We found out that for 50 fs pulses (1850 nm wavelength and 2 x10[superscript]14 W/cm[superscript]2 intensity), D[subscript]2 molecules are 1.15 times more likely to be ionized when the laser field is parallel to the molecular axis than when the laser field is perpendicular. This result agreed perfectly with the result from our ab initio theoretical model and also with predictions of the molecular Ammosov-Delone-Krainov (mo-ADK) theory. In the second part of this work we calculated the time evolution of an initial nuclear wave packet in D[subscript]2[superscript]+ generated by the rapid ionization of D[subscript]2 by an ultra short laser pulse. We Fourier transformed the nuclear probability density with respect to the delay between the pump and probe pulses and obtained two-dimensional internuclear-distance-dependent power spectra which serve as a tool for visualizing and analyzing the nuclear dynamics in D[subscript]2[superscript]+ in an external laser field. We attempt to model realistic laser pulses, therefore in addition to the main spike of the pulse we include the Gaussian pedestal. The optimal laser parameters for observing field-induced bond softening and bond hardening in D[subscript]2[superscript]+ can be achieved by varying the intensity, wavelength, and duration of the probe-pulse pedestal. Despite the implicit "continuum wave" (infinite pulse length) assumption the validity of the "Floquet picture" is tested for the interpretation of short-pulse laser-molecule interactions.

Download or read book Dissociation Dynamics of Diatomic Molecules in Intense Fields written by Maia Magrakvelidze and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We study the dynamics of diatomic molecules (dimers) in intense IR and XUV laser fields theoretically and compare the results with measured data in collaboration with different experimental groups worldwide. The first three chapters of the thesis cover the introduction and the background on solving time-independent and time-dependent Schrödinger equation. The numerical results in this thesis are presented in four chapters, three of which are focused on diatomic molecules in IR fields. The last one concentrates on diatomic molecules in XUV pulses. The study of nuclear dynamics of H2 or D2 molecules in IR pulses is given in Chapter 4. First, we investigate the optimal laser parameters for observing field-induced bond softening and bond hardening in D2. Next, the nuclear dynamics of H2 molecular ions in intense laser fields are investigated by analyzing their fragment kinetic-energy release (KER) spectra as a function of the pump-probe delay [tau]. Lastly, the electron localization is studied for long circularly polarized laser pulses. Chapter 5 covers the dissociation dynamics of O2+ in an IR laser field. The fragment KER spectra are analyzed as a function of the pump-probe delay [tau]. Within the Born-Oppenheimer approximation, we calculate ab-initio adiabatic potential-energy curves and their electric dipole couplings, using the quantum chemistry code GAMESS. In Chapter 6, the dissociation dynamics of the noble gas dimer ions He2+, Ne2+, Ar2+, Kr2+, and Xe2+ is investigated in ultrashort pump and probe laser pulses of different wavelengths. We observe a striking "delay gap" in the pump-probe-delay-dependent KER spectrum only if the probe-pulse wavelength exceeds the pump-pulse wavelength. Comparing pump-probe-pulse-delay dependent KER spectra for different noble gas dimer cations, we quantitatively discuss quantum-mechanical versus classical aspects of the nuclear vibrational motion as a function of the nuclear mass. Chapter 7 focuses on diatomic molecules in XUV laser pulses. We trace the femtosecond nuclear-wave-packet dynamics in ionic states of oxygen and nitrogen diatomic molecules by comparing measured kinetic-energy-release spectra with classical and quantum-mechanical simulations. Experiments were done at the free-electron laser in Hamburg (FLASH) using 38-eV XUV-pump--XUV-probe. The summary and outlook of the work is discussed in Chapter 8.

Download or read book Ab Initio TDDFT Study of Multiphoton Dynamics of Diatomic Molecules in Intense Ultrashort Laser Fields and Quantum Optimal Control Theory written by 陳佑航 and published by . This book was released on 2009 with total page 100 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Asymmetries in Strong field Dynamics of Diatomic Molecules written by Saurabh Mhatre and published by . This book was released on 2023* with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The influence of intense laser fields can cause asymmetries in a target system, either by breaking its symmetry or by suppressing or amplifying its intrinsic asymmetries. These asymmetries allow for coherent control of molecular processes. In this work, we present the numerical investigations that explore the effects of such asymmetries on the fragmentation dynamics of diatomic molecules (specifically, H2+ and HeH+), with a particular focus on the mid-IR pulses. By time-resolved monitoring of the dissociation processes, we observe the mechanism of directional electron localization and tunnel ionization through the asymmetry induced by the phase-controlled two-color pulse in the "symmetric" H2+ system, and the mechanism of "ladder-climbing" pathways in the HeH+ system. We also propose a visualization method for molecular orbitals through the analysis of photoelectron spectra obtained through tunnel ionization investigations. Additionally, we have studied the scarcely researched mass-asymmetry dependent isotope effects in strong fields, which show significant dependence of the dissociation probabilities on the mass-asymmetry.

Download or read book Electronic and nuclear quantum dynamics of molecules in intense laser fields written by Yuichi Fujimura and published by Frontiers Media SA. This book was released on 2023-04-28 with total page 161 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Resolving Strong Field Dynamics in Cation States of CO 2 via Optimised Molecular Alignment written by Malte Oppermann and published by Springer Science & Business Media. This book was released on 2014-04-01 with total page 218 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis presents an experimental study of the ultrafast molecular dynamics of CO_2^+ that are induced by a strong, near-infrared, femtosecond laser pulse. In particular, typical strong field phenomena such as tunneling ionisation, nonsequential double ionisation and photo-induced dissociation are investigated and controlled by employing an experimental technique called impulsive molecular alignment. Here, a first laser pulse fixes the molecule in space, such that the molecular dynamics can be studied as a function of the molecular geometry with a second laser pulse. The experiments are placed within the context of the study and control of ultrafast molecular dynamics, where sub-femtosecond (10^-15 seconds) resolution in ever larger molecular systems represents the current frontier of research. The thesis presents the required background in strong field and molecular physics, femtosecond laser architecture and experimental techniques in a clear and accessible language that does not require any previous knowledge in these fields.

Download or read book Coherence Phenomena in Atoms and Molecules in Laser Fields written by Andre D Bandrauk and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 397 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume contains the lectures and communications presented at the NATO Advanced Research Workshop (NATO ARW 900857) which was held May 5-10, 1991 at McMaster University, Hamilton, Ontario, Canada. A scientific commitee made up of P.P. Lambropoulos (USC & Crete), P.8. Corkum (NRC, Ottawa), and H. B. vL. van den Heuvell (FOM, Amsterdam) guided the organizers, A.D. Bandrauk (Sherbrooke) and S.C. Wallace (Toronto) in preparing a programme which would cover the latest advances in the field of atom and molecule laser interactions. Since the last meeting held in July 1987 on "Atomic and Molecular Processes with Short Intense Laser Pulses", NATO ASI vol 1718 (Plenum Press 1988), considerable progress has been made in understanding high intensity effects on atoms and the concomitant coherence effects. After four years, the emphasis is now shifting more to molecules. The present volume represents therefore this trend with four sections covering the main interests of research endeavours in this area: i) Atoms in Intense Laser-Fields ii) Molecules in Intense Laser Fields iii) Atomic Coherences iv) Molecular Coherences The experience developed over the years in multiphoton atomic processes has been very useful and is the main source of our understanding of similar processes in molecules. Thus ATI (above threshold ionization) has been found to occur in molecules as well as a new phenomenon, ATD (above-threshold dissociation). Laser-induced avoided crossings of molecular electronic surfaces is also now entering the current language of high intensity molecular processes.

Download or read book Molecular Dynamics in Diatomic Molecules with One and Two color Ultrafast Laser Pulses written by Vincent Tagliamonti and published by . This book was released on 2014 with total page 182 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Strong Field Laser Physics written by Thomas Brabec and published by Springer. This book was released on 2008-08-17 with total page 590 pages. Available in PDF, EPUB and Kindle. Book excerpt: Due to the rapid progress in laser technology a wealth of novel fundamental and applied applications of lasers in atomic and plasma physics have become possible. This book focuses on the interaction of high intensity lasers with matter. It reviews the state of the art of high power laser sources, intensity laser-atom and laser-plasma interactions, laser matter interaction at relativistic intensities, and QED with intense lasers.

Download or read book Ionization and Dissociation Dynamics of Molecules in Strong Laser Fields written by Wei Lai and published by . This book was released on 2016 with total page 147 pages. Available in PDF, EPUB and Kindle. Book excerpt: "The fast advancement of ultrashort-pulsed high-intensity laser technology allows for generating an electric field equivalent to the Coulomb field inside an atom or a molecule (e.g., Ec=5.14x109 V/cm at the 1s orbit radius a0=0.0529 nm of the hydrogen atom, which corresponds to an intensity of 3.54x1016 W/cm2). Atoms and molecules exposed in such a field will easily be ionized, as the external field is strong enough to remove the electrons from the core. This is usually referred to "strong field". Strong fields provide a new tool for studying the interaction of atoms and molecules with light in the nonlinear nonperturbative regime. During the past three decades, significant progress has been made in the strong field science. Today, most phenomena involving atoms in strong fields have been relatively well understood by the single-active-electron (SAE) approximation. However, the interpretation of these responses in molecules has encountered great difficulties. Not like atoms that only undergo excitation and ionization, various dissociation channels accompanying excitation and ionization can occur in molecules during the laser pulse interaction, which imparts further complexity to the study of molecules in strong fields. Previous studies have shown that molecules can behave significantly different from rare gas atoms in phenomena as simple as single and double ionization. Molecular dissociation following ionization also presents challenges in strong fields compared to what we have learned in the weak-field regime. This dissertation focuses on experimental studies on ionization and dissociation of some commonly-seen small molecules in strong laser fields. Previous work of molecules in strong fields will be briefly reviewed, particularly on some open questions about multiple dissociation channels, nonsequential double ionization, enhanced ionization and molecular alignment. The identification of various molecular dissociation channels by recent experimental technical upgrades will be shown. The study of enhanced ionization in small molecules by time-resolved pump-probe experiments and varying-pulse duration experiments will be discussed, followed by an investigation of molecular alignment effect in sequential and nonsequential dynamics. At last, selective charge separation in charge asymmetric dissociation of heteronuclear diatomic molecules will be shown and conclusion and future work will be discussed."--Pages vii-viii.

Download or read book Dissociation Dynamics of Molecular Ions in Ultrafast Intense Laser Fields written by Bethany Jochim and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Out of the many tools for probing molecular dynamics, intense, ultrafast laser pulses are particularly well suited for this purpose. First, these pulses have temporal durations shorter than the typical rotational and vibrational periods of molecules and therefore allow the observation of molecular dynamics on their native timescales. Further, the broad bandwidth and high peak intensities of these laser pulses can result in the excitation of many transition pathways that may interfere and enable control of dynamics. The primary focus of this work is the ultrafast laser-induced dissociation of molecular ions. We generate these ions as "fast" beam targets and study their fragmentation using a coincidence three-dimensional (3D) momentum imaging technique, which allows the measurement of all nuclear fragments, including neutrals. This approach is employed to study laser-induced processes in a variety of molecules. The goal of these efforts is not to study specific molecules but rather to use them as testing grounds to deepen our knowledge of laser-induced molecular dynamics in general. For example, we find that permanent-dipole transitions, which are commonly overlooked in the interpretation of strong-field experiments, play a key role in laser-induced dissociation of metastable NO2+ ions. General consideration of these transitions in heteronuclear molecules is important in building our understanding towards more complex molecules. Speaking of more complex systems, we have also begun investigating the laser-induced dynamics of simple hydrocarbons. Our use of molecular ion beam targets gives us the unique ability to exercise control over the initial "configuration," i.e., geometry of these molecules. Utilizing C2H2^q ion beam targets (where q is the molecular ion charge state) prepared in various initial configurations, including acetylene (HCCH), vinylidene (H2CC), and cis/trans, we have determined that this property has an immense impact on the isomerization dynamics, a finding that we anticipate will lead to future work towards deeper understanding. More broadly, this approach of probing molecules in different initial configurations offers a unique perspective that could be complementary to mainstream methods-not just in the case of C2H2 but other chemical systems as well. We also describe some improvements to the 3D momentum imaging methods that facilitate the study of molecular dynamics. One of these developments is a method to distinguish and evaluate the momenta of neutral-neutral channels resulting from the fragmentation of negative ion beams. The second is a technique for imaging the breakup of long-lived metastable molecules decaying in flight to the detector and retrieving the lifetime(s) of the populated states. Our collaborative efforts in adaptive closed-loop control are also discussed. Here, an evolutionary learning algorithm supplied with experimental feedback obtains optimally-shaped ultrashort laser pulses for driving targeted molecular dynamics. While the complexity of the shaped pulses can make interpretation challenging, the combination of these efforts with basic experiments like those we perform using ion beams can help. In closing, the work presented in this thesis extends from diatomic to polyatomic molecules, following the natural progression of building from simpler to more complex systems. We believe that the results of these efforts aid in the advancement of understanding strong-field molecular dynamics and will stimulate future research endeavors along these directions.

Download or read book Atoms Solids and Plasmas in Super Intense Laser Fields written by Dimitri Batani and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 409 pages. Available in PDF, EPUB and Kindle. Book excerpt: The recent developement of high power lasers, delivering femtosecond pulses of 20 2 intensities up to 10 W/cm , has led to the discovery of new phenomena in laser interactions with matter. At these enormous laser intensities, atoms, and molecules are exposed to extreme conditions and new phenomena occur, such as the very rapid multi photon ionization of atomic systems, the emission by these systems of very high order harmonics of the exciting laser light, the Coulomb explosion of molecules, and the acceleration of electrons close to the velocity of light. These phenomena generate new behaviour of bulk matter in intense laser fields, with great potential for wide ranging applications which include the study of ultra-fast processes, the development of high-frequency lasers, and the investigation of the properties of plasmas and condensed matter under extreme conditions of temperature and pressure. In particular, the concept of the "fast ignitor" approach to inertial confinement fusion (ICF) has been proposed, which is based on the separation of the compression and the ignition phases in laser-driven ICF. The aim of this course on "Atom, Solids and Plasmas in Super-Intense Laser fields" was to bring together senior researchers and students in atomic and molecular physics, laser physics, condensed matter and plasma physics, in order to review recent developments in high-intensity laser-matter interactions. The course was held at the Ettore Majorana International Centre for Scientific Culture in Erice from July 8 to July 14,2000.

Download or read book A Framework for Understanding Molecular Dynamics in Strong Laser Fields written by Saipriya V. Menon and published by . This book was released on 2002 with total page 230 pages. Available in PDF, EPUB and Kindle. Book excerpt: