Strong Field Dissociation Dynamics
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Strong Field Dissociation Dynamics
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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.
Dynamics Of Dissociation Versus Ionization In Strong Laser Fields
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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.
Strong Field Dissociation Dynamics
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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.
Strong Field Dynamics And Control Of Molecular Dissociation
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Author :
language : en
Publisher:
Release Date : 2009
Strong Field Dynamics And Control Of Molecular Dissociation written by 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.
Strong field dynamics and control of molecular dissociation.
Ionization And Dissociation Dynamics Of Molecules In Strong Laser Fields
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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.
Strong Field Dynamics And Control Of Molecular Dissociation
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Author : Sarah Roxanna Nichols
language : en
Publisher:
Release Date : 2008
Strong Field Dynamics And Control Of Molecular Dissociation written by Sarah Roxanna Nichols and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2008 with categories.
Resolving Strong Field Dynamics In Cation States Of Co 2 Via Optimised Molecular Alignment
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Author : Malte Oppermann
language : en
Publisher: Springer Science & Business Media
Release Date : 2014-04-01
Resolving Strong Field Dynamics In Cation States Of Co 2 Via Optimised Molecular Alignment written by Malte Oppermann and has been published by Springer Science & Business Media this book supported file pdf, txt, epub, kindle and other format this book has been release on 2014-04-01 with Science categories.
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.
Dissociation Dynamics Of Molecular Ions In Ultrafast Intense Laser Fields
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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 Molecular Ionization
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Author : Timothy Blaise Bohinski
language : en
Publisher:
Release Date : 2015
Strong Field Molecular Ionization written by Timothy Blaise Bohinski 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.
This dissertation investigates the electronic spectroscopy of a series of alkyl phenyl ketone radical cations and the dynamics of selective launch states in the strong field regime with tunable near infrared ultrashort laser pulses from 790 nm - 1550 nm coupled to mass spectrometric detection. Our method relies on tunable strong field laser pulses in the range from 1150 nm - 1550 nm to adiabatically ioinized gas phase molecules and prepare ions in the ground ionic state that serve as a launch state for future excitation and control. Adiabatic ionization is capable of transferring little energy to the molecule and producing a majority of a parent molecular ion in comparison to nonadiabatic ionization wherein multiple ionic states can be populated with an accompanying high degree of molecular fragmentation. We measure a dynamic resonance in the low lying electronic states of the acetopheone radical cation via preparation of a launch state with adiabatic ionization followed by a one photon transition within a single pulse duration which facilitates bond dissociation to produce the benzoyl ion. Experiments on acetophenone homologues and derivatives elucidate the structural dependence of the electronic resonance and supporting ab initio calculations identify the dynamic resonance along the molecular torsional coordinate between the ground ionic state, D0, and second excited state, D2. Post ionization excitation within the pulse duration transfers the ground state wavepacket to the D2 surface where the wavepacket encounters a three state conical intersection that facilitates the preferred bond dissociation. Time resolved photodissociation experiments measure the dynamics of the launch state, large amplitude oscillations and extended coherence times support the notion that adiabatic ionization populates a majority of the ground ionic surface. Control of the dissociation products is initiated from the launch state by varying the pump wavelength and probe intensity. Elimination of the D0 wavepacket with a 1370 nm reveals additional secondary dynamics that are attributed to wavepacket motion on the D2 surface. Finally, the effect of para substitution on the acetophenone radical cation is explored as a strategy to control the launch state wavepacket dynamics. Suppresion of the wavepacket dynamics are observed with the addition of alkoxy groups whereas extended coherence of the launch state dynamics approaching ~5 ps is observed upon trifluoromethyl substitution. A possible mechanism for the extended coherenece based on coupled torsional rotors is proposed.
Coherent Control Over Strong Field Dissociation Of Heteronuclear Diatomic Molecules
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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.