The Liquid State and Its Electrical Properties

Transcription

1 The Liquid State and Its Electrical Properties

2 NATO ASI Series Advanced Science Institutes Series A series presenting the results of activities sponsored by the NA TO Science Committee, which aims at the dissemination of advanced scientific and technological knowledge, with a view to strengthening links between scientific communities. The series is published by an international board of publishers in conjunction with the NATO Scientific Affairs Division A B c o E F G H Life Sciences Physics Mathematical and Physical Sciences Behavioral and Social Sciences Applied Sciences Computer and Systems Sciences Ecological Sciences Cell Biology Plenum Publishing Corporation New York and London Kluwer Academic Publishers Dordrecht, Boston, and London Springer-Verlag Berlin, Heidelberg, New York, London, Paris, and Tokyo Recent Volumes in this Series Volume 186-Simple Molecular Systems at Very High Density edited by A. Pol ian, P. Loubeyre, and N. Boccara Volume 187-X-Ray Spectroscopy in Atomic and Solid State Physics edited by J. Gomes Ferreira and M. Teresa Ramos Volume 188-Reflection High-Energy Electron Diffraction and Reflection Electron Imaging of Surfaces edited by P. K. Larsen and P. J. Dobson Volume 189-Band Structure Engineering in Semiconductor Microstructures edited by R. A. Abram and M. Jaros Volume 190-Squeezed and Nonclassical Light edited by P. Tombesi and E. R. Pike Volume 191-Surface and Interface Characterization by Electron Optical Methods edited by A. Howie and U. Valdre Volume 192-Noise and Nonlinear Phenomena in Nuclear Systems edited by J. L. Munoz-Cobo and F. C. Difilippo Volume 193-The Liquid State and Its Electrical Properties edited by E. E. Kunhardt, L. G. Christophorou, and L. H. Luessen Series B: Physics

3 The Liquid State and Its Electrical Properties Edited by E. E. Ku n hardt Polytechnic University Weber Research Institute Farmingdale, New York L. G. Christophorou Oak Ridge National Laboratory Oak Ridge, Tennessee and L. H. Luessen Naval Surface Warfare Center Dahlgren, Virginia Plenum Press New York and London Published in cooperation with NATO Scientific Affairs Division

4 Proceedings of a NATO Advanced Study Institute International Advanced Course on The Liquid State and Its Electrical Properties, held July 5-17,1987, in Sintra, Portugal Library of Congress Cataloging in Publication Data NATO Advanced Study Institute International Advanced Course on the Liquid State and its Electrical Properties (1987: Sintra, Portugal) The liquid state and its electrical properties I edited by E. E. Kunhardt, L. G. Christophorou, and L. H. Luessen. p. cm.-(nato ASI series. Series B, Physics; v. 193) Bibliography: p. Includes index. ISBN-13: e-isbn-13: : / Liquids-Electric properties-congresses. 2. Fluids-Electric properties Congresses. I. Kunhardt, Erich E. II. Christophorou, L. G. III. Luessen, Lawrence H. IV. Title. V. Series. QC145.4.E45N '2-dc19 CIP 1988 Plenum Press, New York Softcover reprint of the hardcover 1 st edition 1988 A Division of Plenum Publishing Corporation 233 Spring Street, New York, N.Y All rights reserved No part of this book may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, microfilming, recording, or otherwise, without written permission from the Publisher

5 PREFACE As the various disciplines of science advance, they proliferate and tend to become more esoteric. Barriers of specialized terminologies form, which cause scientists to lose contact with their colleagues, and differences in points-of-view emerge which hinder the unification of knowledge among the various disciplines, and even within a given discipline. As a result, the scientist, and especially the student, is in many instances offered fragmented glimpses of subjects that are fundamentally synthetic and that should be treated in their own right. Such seems to be the case of the liquid state. Unlike the other states of matter -- gases, solids, and plasmas -- the liquid state has not yet received unified treatment, probably because it has been the least explored and remains the least understood state of matter. Occasionally, events occur which help remove some of the barriers that separate scientists and disciplines alike. Such an event was the ASI on The Liquid State held this past July at the lovely Hotel Tivoli Sintra, in the picturesque town of Sintra, Portugal, approximately 30 km northwest of Lisbon. Since this broad a subject could not be covered in one Institute, the focus of the ASI was on a theme that provided a common thread of understanding for all in attendance -- the Electrical Properties of the Liquid State. Advances in computational power and diagnostic techniques are increasingly leading to fascinating new results on the basic properties of liquids and the physio-chemical interactions occurring in the liquid phase. Such an understanding will undoubtedly open up new technological applications of the liquid state, and the Sintra ASI was just the right stimulation needed for the seventy-odd scientists and engineers in attendance. Rallying around this theme -- The Liquid State and Its Electrical Properties -- the Institute brought together a remarkable blend of scientists and engineers from the following fields: statistical mechanics, particle kinetics and dynamics, condensed-matter physics, physical chemistry, quantum chemistry, surface chemistry, electro-chemistry, highvoltage engineering, electro-technology, and pulse power. The exposure v

6 of each participant to the diverse concepts and research areas of the others made the Institute a stimulating experience for all. The Institute presented the subject of the liquid state and its electrical properties systematically. The treatment, both theoretical and experimental, started from the microscopic, quantum-statistical foundations of the liquid state and progressed to the macroscopic description of conduction in liquids, and the various applications that arise because of the electrical properties of liquids. Emphasis was placed on fundamental principles and physical points of view, and on achieving a microscopic-macroscopic connection in the description of the liquid state and its electrical properties. The subject matter was organized into four broad areas: (a) Theories of Liquid Structures, (b) Ionic and Electronic Processes, (c) Interfacial Phenomena, and (d) Breakdown and Conduction. These four areas covered the bulk of the Institute. In addition, results of current research were presented in two Poster Sessions, and Future Research Directions and technological innovations derived from liquid-phase studies were discussed in a special session. The session on Theories of Liquid Structures treated the equilibrium properties of simple liquids from a quantum-statistical and statisticalthermodynamics point-of-view. Pair-Correlation Function. The tenor in these presentations was the The various equations that have been proposed to describe its behavior, and techniques for obtaining their solutions (in special cases) were reviewed. with a discussion of electrolytic solutions. These concepts became more "concrete" The session on Ionic and Electronic Processes principally focused on the nature and dynamical behavior of ions and electrons in liquids. A significant amount of time was devoted to the discussion of electron dynamics in liquids. This was a subject of some controversy that gave rise to a number of special discussion sessions that continued to the end of the ASI. Two points of view were expressed: in one, the liquid was modeled as a fluctuating crystal; in the other, the liquid was viewed as a dense gas. The validity of these models obviously depends on the nature of the liquid, e.g., polar, non-polar, liquid rare gases, etc. The discussions focused on the nature of the localized and extended (free) electron states, and, in particular, on the lowest level of a free electron in the liquid, i.e., the "V "level. Accounts were given of the o free electron states, their contribution to the electrical behavior, the relaxation of a hot electron into either the Vo or the localized state, and of the electrical and optical diagnostic techniques which are used in the study to these phenomena. vi

7 These accounts carried the Institute over into the area of Interfacial Phenomena and the question of how electrons are injected from boundaries, as well as the question of the nature of the boundary layers. Experimental methods for investigating interface phenomena were discussed. As the concentration of charge carriers in the liquid increases, space-charge effects become important. Electro-optic techniques used to investigate these effects and other phenomena associated with charge injection were described. Further increases in charged-carrier concentration due to the presence of large applied electric fields eventually leads to the breakdown of the insulating properties of the liquid. This regime was the subject of the last session. In this session, on Breakdown and Conduction, a review was given of the various theories that have been proposed to explain this phenomena. In highly non-uniform fields, the breakdown channel is observed to progress in the form of a "tree" growing from the point of high field stress. Fractal analysis of this evolution has been attempted and this technique was presented. The concept of streamers in liquids -- the propagating "branches" of the breakdown "tree" -- was introduced and related to that in gases. It was suggested that the theories of liquid breakdown and the interpretation of the observed phenomena are phenomenological in nature, and connection to microscopic processes occurring in the liquid must be sought. Clearly, the difficulties encountered in the investigations of the liquid state, which lacks the order of the crystal and the large interparticle distances of the dilute gas, have played a role in slowing down the establishment of a knowledge base from which technological applica~ tions can grow. The development of new methods, both experimental and theoretical, for the study of the liquid state, and the narrowing of the gap between those who study liquids for their own sake and those who utilize the properties of liquids for applications, would greatly advance liquid state technologies. Areas where significant developments were projected include: (a) the quantum statistical description of electrons in liquids using path-integral methods; (b) the optical micro-probing of the liquid state, the dynamical behavior of charges carriers in liquids, the coupling of microscopic and macroscopic processes and properties, and breakdown; (c) the study of model structures and biological systems (structured liquids) and their interaction with radiation; and (d) liquid crystals and gels. vii

8 The comprehensive discussions on the Liquid State and Its Electrical Properties at the Sintra ASI demonstrated that the study of liquids will be a challenging, but rewarding, area for future research and applications. E. Kunhardt Polytechnic University Farmingdale, New York L. G. Christophorou Oak Ridge National Laboratory Oak Ridge, Tennessee L. H. Luessen Naval Surface Warfare Center Dahlgren, Virginia April 1988 viii

9 ACKNOYLEDGMENTS Ye are grateful to a number of organizations for providing the financial assistance that made the Institute possible. Foremost is the NATO Scientific Affairs Division, which provided the single-most financial contribution for the Institute. In addition, the following US sources made contributions: Naval Surface Yarfare Center, Office of Naval Research, Army Electronics Technology and Devices Laboratory, and Los Alamos National Laboratory. The Editors also wish to acknowledge the following individuals: Mrs. Ann Drury, Polytechnic University, and Mrs. Linda Johnson, Naval Surface Yarfare Center, the Institute's Administrative Coordinators for Lectures and Participants, respectively; Ms. Susie M. Anderson, Supervisor for Yord Processing at the EG&G Yashington Analytical Services Center Office at Dahlgren, Virginia, which had the task of centrally retyping every lecturer's manuscript and producing a camera-ready document for delivery to Plenum Corporation; Mrs. Barbara Kester of the Publications CoordiQation Office; and finally to the staff and management of the Hotel Tivoli Sintra -- their efforts, along with the natural beauty and charm of Sintra, and the wonderful accommodations and facilities of the Hotel, made this two-week ASI one we will all remember for years to come.

10 CONTENTS THEORIES OF LIQUID STRUCTURE Field Theoretic Models of Liquids D. Chandler The Structure of Simple Fluids D. A. McQuarrie Dynamic Processes in Liquids and Selected Topics Related to the Dynamics of Ions and Electrons in Liquids J. B. Hubbard IONIC AND ELECTRONIC PROCESSES Theories of Electrolyte Solutions J. C. Rasaiah Theoretical Studies of Electrons in Fluids N. R. Kestner Geometrical Perspectives of a Solvated Electron D. Chandler Electron Localization and Femtosecond Nonlinear Optical Responses in Liquids.. G. A. Kenney-Wallace Strong Field Effects and Molecular Dynamics Simulations M. Golombok and G. A. Kenney-Wallace Electron Kinetics in Nonpolar Liquids -- Energy and Pressure Effects.. R. Holroyd Photoconductivity, Conduction Electron Energies, and Excitons in Simple Fluids... I. T. Steinberger Electron Scattering and Mobility in Dielectric Liquids G. R. Freeman Hot Electron Mobility and Electron Attachment in Non-Polar Liquids.... Y. F. Schmidt xi

11 Gas/Liquid Transition: Interphase Physics L. G. Christophorou Calculations of Vo and the Energy Dispersion of Electrons in Rare Gas Liquids... G. Ascarelli INTERFACIAL PHENOMENA Electrical Aspects of Liquid/Vapor, Liquid/Liquid, and Liquid/Metal Interfaces..... B. E. Conway Space Charge Effects in Dielectric Liquids M. Zahn BREAKDOWN AND CONDUCTION An Overview of Electrical Processes Leading to Dielectric Breakdown of Liquids. T. J. Lewis Electron Scattering and Dielectric Breakdown in Liquid and Solid Dielectrics... H. R. Zeller and E. Cartier Streamers in Liquids R. E. Tobazeon Electric Conduction in Dielectric Liquids.. J. P. Gosse Measurement of Electrical Breakdown in Liquids R. E. Hebner Appendix A: Appendix B: Appendix C: Appendix D: APPENDICES Abstracts of Poster Papers Organizing Committee Lecturers Participants Index xii