Relaxation Processes in Electronically Excited Polyatomic Molecules PDF Download

Author: Graham Richard Fleming
Publisher:
ISBN:
Category :
Languages : en
Pages : 398

View

Book Description

Author: J. Fünfschilling
Publisher: Springer Science & Business Media
ISBN: 9400908636
Category : Science
Languages : en
Pages : 282

View

Book Description
Relaxation phenomena of excited molecular states are abundant in all nature. They mediate such key processes as photochemical reactions or even the pathways of ordinary chemical reactions. However, for a long time the main research in electronic relaxation processes was concerned with anorganic solids, in part because of their great technological importance (photography, semiconductors ... ) in part also because these compounds were the "workhorses" of the solid state physicists. In the last 30 years, there was a steadily increasing interest in organic molecular systems, first in molecular crystals and later in all forms of molecular solids (glasses, polymers, membranes, ... ). The present volume combines papers on quite different types of relaxation phenomena: the type of solid studied, the electronic states involved, the physical processes responsible for the relaxations are all different. Nevertheless, after reading this book, a more clear and complete picture of the phenomenon "relaxa tion" emerges that proves that this volume is more than just a collection of individual articles. The volume starts with the paper "Spin-lattice and spin-spin relaxation in photo-excited triplet states in molecular crystals" by Jan Schmidt. Even in these seemingly simple systems of isolated guest molecules in a single crystal host, the relaxation phenomena are quite involved and a very thorough investigation is necessary to find the key relaxation processes. The end of the article provides a bridge to the following paper: it treats interactions of two molecules (dimers), where resonant interactions become important and lead to new, characteristic relaxation processes.

Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :

View

Book Description
Excitation energy dependence of radiationless decay rate under collision-free conditions was utilized as a probe of intramolecular vibrational relaxation in tetracene and pentacene. The results give evidence of vibrational relaxation which competes with electronic relaxation. The substitution dependence of T/sub 1/(n.pi.*) .-->. S/sub 0/ radiationless transition in monocyclic diazines and the temperature dependence of S/sub 1/ non-radiative decay rate in alcoholic solutions of polycyclic monoazines indicate that the vibronic interaction between the lowest energy n.pi.* and .pi pi.* states leads to a rapid radiationless deactivation of the lower of the two electronic states. Finally, a photon-counting spectrofluorometer of very high sensitivity was constructed, and it was used to record T/sub 2/ .-->. T/sub 1/ fluorescence in bromoanthracenes and S/sub 2/ .-->. S/sub 1/ fluorescence in azulene. These spectra represent the first bona-fide, or the most convincing, observation of fluorescence between excited electronic states.

Author: Sheng Lin
Publisher: Elsevier
ISBN: 0323150276
Category : Science
Languages : en
Pages : 440

View

Book Description
Radiationless Transitions is a critical discussion of research studies on the theory and experiments in radiationless transitions. This book is composed of nine chapters, and begins with discussions on the theory and experiment of photophysical processes of single vibronic levels and/or single rovibronic levels. The subsequent chapters deal with the spectroscopic investigations of intramolecular vibrational relaxation; the dynamics of molecular excitation by light; and the photophysical processes of small molecules in condensed phase. The discussions then shift to the high pressure effects on molecular luminescence and the internal conversion involving localized excitations, presenting one qualitative and one quantitative example, as well as the intersystem crossing with localized excitations. A chapter explores the energy transfer processes that occur after a molecule in solution is excited by light, with an emphasis on solid solutions in which the large amplitude molecular motion is largely quenched. This chapter also looks into the liquid solutions in which the molecules can translate and rotate under the influence of fluctuating forces from the liquid. The concluding chapter focuses on ultrafast processes. Researchers in the fields of physics, chemistry, and biology will benefit from this book.

Author: Ėmilʹ Samuilovich Medvedev
Publisher: Springer
ISBN:
Category : Science
Languages : en
Pages : 396

View

Book Description
Radiationless Transitions in Polyatomic Molecules treats the dynamics of electronically excited states and the transition probabilities of electronic relaxation processes. Based on a simple and transparent, yet rigorous presentation of the basic physical concepts, the mathematical methods required are developed in detail from first principles and new light shed on the treatment of traditional issues.

Author: Alexander Fridman
Publisher: CRC Press
ISBN: 9781560328483
Category : Science
Languages : en
Pages : 888

View

Book Description
Plasma engineering is a rapidly expanding area of science and technology with increasing numbers of engineers using plasma processes over a wide range of applications. An essential tool for understanding this dynamic field, Plasma Physics and Engineering provides a clear, fundamental introduction to virtually all aspects of modern plasma science and technology, including plasma chemistry and engineering, combustion, chemical physics, lasers, electronics, methods of material treatment, fuel conversion, and environmental control. The book contains an extensive database on plasma kinetics and thermodynamics, many helpful numerical formulas for practical calculations, and an array of problems and concept questions.

Author: Robert Steiner
Publisher: Springer Science & Business Media
ISBN: 1461593344
Category : Science
Languages : en
Pages : 268

View

Book Description
During the past decade, fluorescence techniques have come to occupy a position of central importance in biochemistry. Such areas as laser techniques, radiation less energy transfer, and nanosecond fluorometry have evolved from esoteric research specialties into standard procedures that are applied routinely to bio chemical problems. Indeed, discussion of the above three areas occupies the greater part of this book. Its level and approach are appropriate for the bio logical or physical scientist who is interested in applying fluorescence techniques, but is not necessarily an expert in this area. The coverage of the literature has, in general, been selective rather than exhaustive. It is likely that what is summarized here will prove resistant to the erosion of time and provide a basis for the future evolution of this rapidly developing area of science. Robert F. Steiner Catonsville, Maryland vii Contents Chapter 1 Some Principles Governing the Luminescence of Organic Molecules R. M Hochstrasser 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 2. Spontaneous Emission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 2. 1. General Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 2. 2. Luminescence from Nearby States . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. 3. Multiple State Decay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Molecular Luminescence Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . 5 3. 1. The Transition Dipole Moment . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 3. 2. Determination of Transition-Moment Directions from Fluorescence . . . 8 3. 3. Polarization of Fluorescence from Crystals. . . . . . . . . . . . . . . . . . . . 9 4. Principles of Luminescence Experiments Carried Out with Lasers. . . . . . . 12 4. 1. Nonlinear Processes and Optical Pumping . . . . . . . . . . . . . . . . . . . 12 5. Coherent Interactions of Molecules and Light . . . . . . . . . . . . . . . . . . . . 16 5. 1. The Distinctions between Fluorescence and Resonance Raman Effects 17 6. Ultrafast Fluorescence Decay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Author: Vladilen Stepanovich Letokhov
Publisher: CRC Press
ISBN: 1000447855
Category : Science
Languages : en
Pages : 358

View

Book Description
Laser spectroscopy has been perfected over the last fifteen years to become a precise tool for the investigation of highly vibrationally excited molecules. Intense infrared laser radiation permits both the multiple-photon resonant excitation and the dissociation of polyatomic molecules. In this book, the latest results of some of the foremost Soviet researchers are published for the first time in the West. Laser Spectroscopy of Highly Vibrationally Excited Molecules contains a comprehensive study of both the experimental and theoretical aspects of the basic photophysical interactions that occur in these processes. The book first focuses on the nonlinear interaction between the resonant vibrational mode and the intense infrared field and then examines the nonlinear interaction between the vibrational modes themselves due to anharmonicity. These interrelated processes determine all the characteristics of polyatomic molecules in an infrared field. The book also discusses related phenomena such as spectra broadening, optical resonance, photon echoes, and dynamical chaos. It includes examples of multiple-photon resonant excitation such as the excitation of OsO4 by CO^O2 laser radiation, which is detected by the visible luminescence that results. This book will be of great interest to researchers and postgraduate students in infrared laser spectroscopy and the laser chemistry of molecules and applications of isotope separation.

Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 17

View

Book Description
The transfer of energy in isolated or colliding molecules is a fundamental process with practical consequences for complex phenomena occurring in atmospheric chemistry, combustion, molecular lasers, plasmas, and a host of other environments containing energetic species. We have developed a technique that combines vibrational overtone excitation, to prepare highly vibrationally excited initial states, and time-resolved spectroscopic detection, to probe the evolution of the prepared state, for studying energy transfer in vibrationally energized molecules. We have used this approach to determine directly, for the first time, the frequencies of the three ungerade vibrations in the first electronically excited state of acetylene. Using this information we have characterized highly vibrationally excited states of acetylene and directly the frequencies and rotational constants of the perturbing vibrational states at these energies. Combining these spectroscopic insights on the vibrationally and electronically excited states of acetylene has allowed us to determine the energy transfer rates and pathways in the collisional relaxation of a polyatomic molecule containing 10,000 cm-1 of vibrational energy, Rotational energy transfer is very rapid, occurring on about every other collision, but is essentially unaffected by the identity of the vibrational state in which the rotational relaxation occurs.

Author: Alexander Fridman
Publisher: John Wiley & Sons
ISBN: 3527349545
Category : Technology & Engineering
Languages : en
Pages : 805

View

Book Description
Plasma Science and Technology An accessible introduction to the fundamentals of plasma science and its applications In Plasma Science and Technology: Lectures in Physics, Chemistry, Biology, and Engineering, distinguished researcher Dr. Alexander Fridman delivers a comprehensive introduction to plasma technology, including fulsome descriptions of the fundamentals of plasmas and discharges. The author discusses a wide variety of practical applications of the technology to medicine, energy, catalysis, coatings, and more, emphasizing engineering and science fundamentals. Offering readers illuminating problems and concept questions to support understanding and self-study, the book also details organic and inorganic applications of plasma technologies, demonstrating its use in nature, in the lab, and in both novel and well-known applications. Readers will also find: A thorough introduction to the kinetics of excited atoms and molecules Comprehensive explorations of non-equilibrium atmospheric pressure cold discharges Practical discussions of plasma processing in microelectronics and other micro-technologies Expert treatments of plasma in environmental control technologies, including the cleaning of air, exhaust gases, water, and soil Perfect for students of chemical engineering, physics, and chemistry, Plasma Science and Technology will also benefit professionals working in these fields who seek a contemporary refresher in the fundamentals of plasma science and its applications.