Dissociation Dynamics Of Diatomic Molecules In Intense Fields
DOWNLOAD
Download Dissociation Dynamics Of Diatomic Molecules In Intense Fields PDF/ePub or read online books in Mobi eBooks. Click Download or Read Online button to get Dissociation Dynamics Of Diatomic Molecules In Intense Fields book now. This website allows unlimited access to, at the time of writing, more than 1.5 million titles, including hundreds of thousands of titles in various foreign languages. If the content not found or just blank you must refresh this page
Dissociation Dynamics Of Diatomic Molecules In Intense Fields
DOWNLOAD
Author : Maia Magrakvelidze
language : en
Publisher:
Release Date : 2013
Dissociation Dynamics Of Diatomic Molecules In Intense Fields written by Maia Magrakvelidze and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013 with categories.
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.
Ionization And Dissociation Dynamics Of Molecules In Strong Laser Fields
DOWNLOAD
Author : Wei Lai
language : en
Publisher:
Release Date : 2016
Ionization And Dissociation Dynamics Of Molecules In Strong Laser Fields written by Wei Lai and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016 with categories.
"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.
Dissociation Dynamics Of Molecular Ions In Ultrafast Intense Laser Fields
DOWNLOAD
Author : Bethany Jochim
language : en
Publisher:
Release Date : 2019
Dissociation Dynamics Of Molecular Ions In Ultrafast Intense Laser Fields written by Bethany Jochim and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2019 with categories.
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.
Strong Field Dissociation Dynamics
DOWNLOAD
Author :
language : en
Publisher:
Release Date : 1993
Strong Field Dissociation Dynamics written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1993 with categories.
The strong-field dissociation behavior of diatomic molecules is examined under two distinctive physical scenarios. In the first scenario, the dissociation of the isolated hydrogen and deuterium molecular ions is discussed. The dynamics of above-threshold dissociation (ATD) are investigated over a wide range of green and infrared intensities and compared to a dressed-state model. The second situation arises when strong-field neutral dissociation is followed by ionization of the atomic fragments. The study results in a direct measure of the atomic fragment's ac-Stark shift by observing the intensity-dependent shifts in the electron or nuclear fragment kinetic energy. 8 figs., 14 refs.
Coherent Control Over Strong Field Dissociation Of Heteronuclear Diatomic Molecules
DOWNLOAD
Author : Brandon Rigsbee
language : en
Publisher:
Release Date : 2015
Coherent Control Over Strong Field Dissociation Of Heteronuclear Diatomic Molecules written by Brandon Rigsbee and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2015 with categories.
In the last 20 years, advancements in laser technology have allowed for the production of intense laser pulses with durations in the femtosecond (10−15 second) regime, giving scientists the ability to probe nuclear dynamics on their natural time scale. Study of the dissociated fragments created by these intense fields can be used to learn about the molecular structure and dynamics. The work presented in this thesis focuses on controlling this light-molecule interaction in such a way that we can preferentially dissociate the molecule to a desired final product. The hydrogen molecular ion, HD, as well as LiF serve as simple systems that can be studied theoretically for a broad range of laser parameters. Our goal in using these relatively simple systems is to capture the essential physics of the light-molecule interaction and develop general methods to describe these interactions in more complex systems.
The Spectra And Dynamics Of Diatomic Molecules
DOWNLOAD
Author : Helene Lefebvre-Brion
language : en
Publisher: Academic Press
Release Date : 2004-04-02
The Spectra And Dynamics Of Diatomic Molecules written by Helene Lefebvre-Brion and has been published by Academic Press this book supported file pdf, txt, epub, kindle and other format this book has been release on 2004-04-02 with Science categories.
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.-
Dynamics Of Diatomic Molecules In Intense Fields
DOWNLOAD
Author : Liang-You Peng
language : en
Publisher:
Release Date : 2005
Dynamics Of Diatomic Molecules In Intense Fields written by Liang-You Peng and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2005 with categories.
Asymmetries In Strong Field Dynamics Of Diatomic Molecules
DOWNLOAD
Author : Saurabh Mhatre
language : de
Publisher:
Release Date : 2023*
Asymmetries In Strong Field Dynamics Of Diatomic Molecules written by Saurabh Mhatre and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2023* with categories.
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.
Nuclear Dynamics And Ionization Of Diatomic Molecules In Intense Laser Fields
DOWNLOAD
Author : Maia Magrakvelidze
language : en
Publisher:
Release Date : 2009
Nuclear Dynamics And Ionization Of Diatomic Molecules In Intense Laser Fields written by Maia Magrakvelidze and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2009 with categories.
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.
Dynamics Of Dissociation Versus Ionization In Strong Laser Fields
DOWNLOAD
Author :
language : en
Publisher:
Release Date : 1993
Dynamics Of Dissociation Versus Ionization In Strong Laser Fields written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1993 with categories.
In this paper, experimental results are presented which clearly demonstrate the effectiveness that an external field has in altering the dissociation dynamics. The experiment examines the strong-field dissociation dynamics of molecular hydrogen ions and its deuterated isotopes. These studies involve multiphoton excitation in the intensity regime of 10[sup 11-14] W/cm[sup 2] with the fundamental and second harmonic of a ND:YAG or ND:YLF laser system. Measurements include energy resolved electron and mass spectroscopy which provide useful probes in elucidating the interaction dynamics predicted by existing models. The example this in this paper, examines the strong-field dissociation of H[sub 2][sup +], HD[sup +], and D[sub 2][sup +] at green (0.5 [mu]m) and (1[mu]m) frequencies. The diatomic ions are formed via multiphonon ionization of the neutral precursor which is physically separable from the dissociation process. This study provides the first observation of the dynamics associated with the above threshold dissociation (ATD) process and analogies will be made with the more familiar above threshold ionization (ATI) phenomenon.