Femtosecond Photoelectron Spectroscopy: a New Tool for the Study of Anion Dynamics

Femtosecond Photoelectron Spectroscopy: a New Tool for the Study of Anion Dynamics
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Publisher:
Total Pages:
Release: 2003
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A new experimental technique for the time-resolved study of anion reactions is presented. Using femtosecond laser pulses, which provide extremely fast ([approx] 100 fs) time resolution, in conjunction with photoelectron spectroscopy, which reveals differences between anion and neutral potential energy surfaces, a complex anion reaction can be followed from its inception through the formation of asymptotic products. Experimental data can be modeled quantitatively using established theoretical approaches, allowing for the refinement of potential energy surfaces as well as dynamical models. After a brief overview, a detailed account of the construction of the experimental apparatus is presented. Documentation of the data acquisition program is contained in the Appendix. The first experimental demonstration of the technique is then presented for I[sub 2][sup -] photodissociation, modeled using a simulation program which is also detailed in the Appendix. The investigation of I[sub 2][sup -] photodissociation in several size-selected I[sub 2][sup -](Ar)[sub n] (n= 6-20) and I[sub 2][sup -](CO[sub 2])[sub n] (n= 4-16) clusters forms the heart of the dissertation. In a series of chapters, the numerous effects of solvation on this fundamental bond-breaking reaction are explored, the most notable of which is the recombination of I[sub 2][sup -] on the ground[tilde X]([sup 2][Sigma][sub u][sup+]) state in sufficiently large clusters. Recombination and trapping of I[sub 2][sup -] on the excited[tilde A]([sup 2][Pi][sub 3/2,g]) state is also observed in both types of clusters. The studies have revealed electronic state transitions, the first step in recombination, on a[approx]500 fs to[approx]10 ps timescale. Accompanying the changes in electronic state is solvent reorganization, which occurs on a similar timescale. Over longer periods ([approx]1 ps to & gt;200 ps), energy is transferred from vibrationally excite d I[sub 2][sup -] to modes of the solvent, which in turn leads to solvent evaporation. These effects become more important as cluster size increases. In addition, differences in timescale and mechanism are observed between clusters of Ar, which binds to I[sup -] and I[sub 2][sup -] rather weakly, and CO[sub 2], whose large quadruple moment allows substantially stronger binding to these anions.

Advances in Chemical Reaction Dynamics

Advances in Chemical Reaction Dynamics
Author: Peter M. Rentzepis
Publisher: Springer Science & Business Media
Total Pages: 608
Release: 2012-12-06
Genre: Science
ISBN: 9400947348

This book contains the formal lectures and contributed papers presented at the NATO Advanced Study Institute on. the Advances in Chemical Reaction Dynamics. The meeting convened at the city of Iraklion, Crete, Greece on 25 August 1985 and continued to 7 September 1985. The material presented describes the fundamental and recent advances in experimental and theoretical aspects of, reaction dynamics. A large section is devoted to electronically excited states, ionic species, and free radicals, relevant to chemical sys tems. In addition recent advances in gas phase polymerization, formation of clusters, and energy release processes in energetic materials were presented. Selected papers deal with topics such as the dynamics of electric field effects in low polar solutions, high electric field perturbations and relaxation of dipole equilibria, correlation in picosecond/laser pulse scattering, and applications to fast reaction dynamics. Picosecond transient Raman spectroscopy which has been used for the elucidation of reaction dynamics and structural changes occurring during the course of ultrafast chemical reactions; propagation of turbulent flames and detonations in gaseousĀ· energetic systems are also discussed in some detail. In addition a large portion of the program was devoted to current experimental and theoretical studies of the structure of the transition state as inferred from product state distributions; translational energy release in the photodissociation of aromatic molecules; intramolecu lar and intraionic dynamic processes.

Conical Intersections

Conical Intersections
Author: Wolfgang Domcke
Publisher: World Scientific
Total Pages: 769
Release: 2011
Genre: Science
ISBN: 9814313440

The concept of adiabatic electronic potential-energy surfaces, defined by the Born?Oppenheimer approximation, is fundamental to our thinking about chemical processes. Recent computational as well as experimental studies have produced ample evidence that the so-called conical intersections of electronic energy surfaces, predicted by von Neumann and Wigner in 1929, are the rule rather than the exception in polyatomic molecules. It is nowadays increasingly recognized that conical intersections play a key mechanistic role in chemical reaction dynamics. This volume provides an up-to-date overview of the multi-faceted research on the role of conical intersections in photochemistry and photobiology, including basic theoretical concepts, novel computational strategies as well as innovative experiments. The contents and discussions will be of value to advanced students and researchers in photochemistry, molecular spectroscopy and related areas.

Modern Trends In Chemical Reaction Dynamics - Part Ii: Experiment And Theory

Modern Trends In Chemical Reaction Dynamics - Part Ii: Experiment And Theory
Author: Kopin Liu
Publisher: World Scientific
Total Pages: 539
Release: 2004-11-22
Genre: Science
ISBN: 9814482277

The field of chemical reaction dynamics has made tremendous progress during the last decade or so. This is due largely to the development of many new, state-of-the-art experimental and theoretical techniques during that period. It is beneficial to present these advances, both theoretical and experimental, in a review volume (Parts I and II). The primary purpose of this review volume is to provide graduate students and experts in the field with a rather detailed picture of the current status of advanced experimental and theoretical research in chemical reaction dynamics. All chapters in these two parts have been written by world-renowned experts active in such research.

Photoionization and Photodetachment

Photoionization and Photodetachment
Author: Cheuk-Yiu Ng
Publisher: World Scientific
Total Pages: 1415
Release: 2000
Genre: Science
ISBN: 9812813470

Owing to the advances of vacuum ultraviolet and ultrafast lasers and third generation synchrotron sources, the research on photoionization, photoelectrons, and photodetachment has gained much vitality in recent years. These new light sources, together with ingenious experimental techniques, such as the coincidence imaging, molecular beam, pulsed field ionization photoelectron, mass-analyzed threshold ion, and pulsed field ion pair schemes, have allowed spectroscopic, dynamic, and energetic studies of gaseous species to a new level of detail and accuracy. Profitable applications of these methods to liquids are emerging.This invaluable two-volume review consists of twenty-two chapters, focusing on recent developments in photoionization and photodetachment studies of atoms; molecules, transient species, clusters, and liquids.