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Author: Katrin Reininger
Publisher:
ISBN:
Category : Molecular dynamics
Languages : en
Pages :
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Author: Katrin Reininger
Publisher:
ISBN:
Category : Molecular dynamics
Languages : en
Pages :
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Author: Malte Oppermann
Publisher: Springer Science & Business Media
ISBN: 3319053388
Category : Science
Languages : en
Pages : 218
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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.
Author: Craig S. Slater
Publisher: Springer
ISBN: 3319245171
Category : Science
Languages : en
Pages : 194
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The work presented in this thesis involves a number of sophisticated experiments highlighting novel applications of the Pixel Imaging Mass Spectrometry (PImMS) camera in the field of photoinduced molecular dynamics. This approach represents the union of a new enabling technology (a multiple memory register, CMOS-based pixel detector) with several modern chemical physics approaches and represents a significant leap forward in capabilities. Applications demonstrated include three-dimensional imaging of photofragment Newton spheres, simultaneous electron-ion detection using a single sensor, and ion-ion velocity correlation measurements that open the door to novel covariance imaging experiments. When combined with Coulomb explosion imaging, such an approach is demonstrated to allow the measurement of molecular structure and motion on a femtosecond timescale. This is illustrated through the controlled photoexcitation of torsional motion in biphenyl molecules and the subsequent real-time measurement of the torsional angle.
Author: C. D. Lin
Publisher: Cambridge University Press
ISBN: 1107197767
Category : Science
Languages : en
Pages : 419
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Book Description
An introductory textbook on attosecond and strong field physics, covering fundamental theory and modeling techniques, as well as future opportunities and challenges.
Author: Weifeng Yang
Publisher: Frontiers Media SA
ISBN: 2832522750
Category : Science
Languages : en
Pages : 88
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Author: James Michael Glownia
Publisher:
ISBN:
Category :
Languages : en
Pages :
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In this thesis I will describe some of the techniques we have developed to extract coherent vibrational and rotational wavepacket motion from stochastic ultrafast free electron x-ray light sources such as the Linac Coherent Light Source. In the initial experiments we performed, the ultrafast x-rays themselves created vibrational wavepackets that were probed by an ultrafast optical laser, and to the best of our knowledge this is the first example of ultrafast coherent preparation of a wavepacket using x-rays. The x-rays were also utilized to probe rotational wavepackets formed by the optical laser. These findings led to a second series of experiments where we sought to use the x-rays as a probe of non Born-Oppenheimer dynamics. The first time-resolved x-ray/optical pump-probe experiments at the SLAC Linac Coherent Light Source (LCLS) used a combination of feedback methods and post-analysis binning techniques to synchronize an ultrafast optical laser to the linac-based x-ray laser. Transient molecular nitrogen alignment revival features produced by coherent rotational wavepackets were resolved in time-dependent x-ray-induced fragmentation spectra. These alignment features were used to find the temporal overlap of the pump and probe pulses. The strong-field dissociation of x-ray generated quasi-bound molecular dications was used to establish the residual timing jitter. This analysis shows that the relative arrival time of the Ti:Sapphire laser and the x-ray pulses had a distribution with a standard deviation of approximately 120 fs. To overcome this limitation we analyzed the ion time of flight traces using a manifold embedding and nonlinear singular value decomposition techniques in collaboration with Abbas Ourmazd and Russell Fung at the University of Wisconsin Milwaukee. This analysis automatically separated the alignment and dication dissociation dynamics from the data, and it revealed fast dynamics that we can attribute to coherent vibrational wavepackets that were created by the ultrafast x-rays and probed by the optical laser. A second study we performed looked at the feasibility of using the LCLS as a fast Coulomb explosion probe of systems undergoing fast laser induced dynamics beyond molecular alignment. As the primary mechanism of energy transfer in natural chemical systems, developing a fundamental understanding of non-radiative excited-state transfer via conical-intersections is of utmost importance for many fields such as biochemistry, alternative energy research, and quantum control. In general, the relevant chemical systems are complex and the exact energy transfer pathways are hard to discriminate from other dynamics. We conducted an experiment to use ultrafast optical and x-ray lasers to induce and observe time resolved molecular dynamics of an optically induced conical-intersection in a prototype system of molecular iodine. Few-femtosecond x-ray pulses from the LCLS then rapidly ionized the molecules without additional strong-field dressing of the potential energy surfaces under investigation. We used optically-dressed molecular iodine as a well controllable analog of a natural conical-intersections. Additionally, we implemented a molecular alignment technique that should prove generally applicable to numerous future LCLS experiments and may compliment condensed-phase x-ray imaging studies of molecular dynamics.
Author: Benjamin J. Whitaker
Publisher: Cambridge University Press
ISBN: 1139437909
Category : Science
Languages : en
Pages : 269
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Book Description
Charged particle imaging has revolutionized experimental studies of photodissociation and bimolecular collisions over the past couple of decades. Written in a tutorial style by some of the key practitioners in the field, this book gives a comprehensive account of the technique and describes many of its applications.
Author: Bretislav Friedrich
Publisher: Springer Nature
ISBN: 3030639630
Category : Science
Languages : en
Pages : 639
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Book Description
This Open Access book gives a comprehensive account of both the history and current achievements of molecular beam research. In 1919, Otto Stern launched the revolutionary molecular beam technique. This technique made it possible to send atoms and molecules with well-defined momentum through vacuum and to measure with high accuracy the deflections they underwent when acted upon by transversal forces. These measurements revealed unforeseen quantum properties of nuclei, atoms, and molecules that became the basis for our current understanding of quantum matter. This volume shows that many key areas of modern physics and chemistry owe their beginnings to the seminal molecular beam work of Otto Stern and his school. Written by internationally recognized experts, the contributions in this volume will help experienced researchers and incoming graduate students alike to keep abreast of current developments in molecular beam research as well as to appreciate the history and evolution of this powerful method and the knowledge it reveals.
Author: Takayoshi Kobayashi
Publisher: Springer Science & Business Media
ISBN: 9783540241102
Category : Science
Languages : en
Pages : 954
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Book Description
Ultrafast Phenomena XIV presents the latest advances in ultrafast science, including ultrafast laser and measurement technology as well as studies of ultrafast phenomena. Pico-, femto-, and atosecond processes relevant in physics, chemistry, biology and engineering are presented. Ultrafast technology is now having a profound impact within a wide range of applications, among them imaging, material diagnostics, and transformation and high-speed optoelectronics. This book summarizes results presented at the 14th Ultrafast Phenomena Conference and reviews the state of the art in this important and rapidly advancing field.
Author: Travis Severt
Publisher:
ISBN:
Category :
Languages : en
Pages :
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When a molecule absorbs energy from its surrounding environment, the molecule's structure begins to evolve. Understanding this evolution at a fundamental level can help researchers, for example, steer chemical reactions to more favorable outcomes. The research reported in this thesis aims to further knowledge about molecular fragmentation dynamics using coincidence three-dimensional momentum imaging. To achieve this goal, we use a combination of ultrafast, intense laser pulses and vacuum-ultraviolet single-photon absorption to initiate and probe molecular dynamics. Specifically, ultrafast lasers allow researchers to follow and control molecular dynamics on their natural time scales. To complement such studies, we also use vacuum-ultraviolet single-photon absorption, in conjunction with the coincidence momentum imaging of all ejected fragments including electrons, to pinpoint state-selective dynamics occurring in various molecular targets. Throughout the thesis, we are interested in several different classes of molecular dynamics. First is the sequential fragmentation of molecules, where two or more bonds break in a step-wise manner. Specifically, we developed the native-frames analysis method, which is used to systematically reduce the dimensionality of multi-body fragmentation using the conjugate momenta of Jacobi coordinates. Applying this framework, we identify the signature of sequential fragmentation and separate its distribution from other competing processes. Moreover, we highlight the method's strengths by following fragmentation dynamics step-by-step and state-selectively using the single-photon double-ionization of D2O as an example. In addition, we explore how the signature of sequential fragmentation within the native-frames method may change under different initial conditions and demonstrate the first steps toward expanding the method to four-body breakup using formic acid as an example. In the future, we hope to identify exotic sequential fragmentation pathways where two or more metastable intermediates are formed together. We also explore molecular isomerization and roaming dynamics leading to bond rearrangement. Specifically, we demonstrate that bond-rearrangement branching ratios in several triatomic molecules are approximately the same order of magnitude. Furthermore, we highlight that the formation of H3 in various alcohol molecules can occur via roaming of H2 molecules. In addition, we study the coherent control of several molecular ions, demonstrating that the CS2+ molecule fragments via a pump-dump mechanism that occurs in a single laser pulse. We also explore the two-color control of D2+ dissociation. Specifically, we observe phase shifts between pathways originating from different initial vibrational levels corresponding to "time-delays" of 10's of attoseconds, showing that such time-scales are not just accessible via electron dynamics. Since single vacuum-ultraviolet photon absorption experiments have proven to be powerful in studying molecular fragmentation dynamics, we investigate the enhancement of lab-based high-order harmonic generation photon sources driven by two-color laser fields. Specifically, we show that two-color 800-400-nm and 800-266-nm driving fields outperform the single-color 800-nm driver by more than an order of magnitude for the plateau harmonics. Furthermore, we demonstrate that the 800-266-nm bichromatic field can control the excursion time of an electron's trajectory by as much as a factor of 2. This result is important for techniques that use the rescattering electron wavepacket as a probe for molecular dynamics, such as in laser-induced electron diffraction (LIED) and high-harmonic spectroscopy (HHS) techniques. Finally, we highlight an upgrade of our coincidence three-dimensional momentum imaging method to measure breakup channels of molecular ions where the fragments have large mass-to-charge ratio differences. Specifically, we detect the light ions, such as H+ and H2+, by adding a second movable offset detector closer to the interaction region. Meanwhile, the heavy ions and neutral fragments fly underneath the new detector and are measured using the original downstream detector, as demonstrated with preliminary CD2+ measurements. In closing, this thesis covers a variety of topics with the common theme of better understanding molecular fragmentation dynamics, ranging from multi-body fragmentation dynamics to isomerization, roaming, and coherent control. In addition, we discuss enhancing high-harmonic-generation-based photon sources to help assist in such studies in the future. Overall, we believe the results presented throughout this thesis contribute to the advancement of molecular dynamics research
