Table Of Content

This page intentionally left blank positron physics This book provides a comprehensive and up-to-date account of the field of low energy positrons and positronium within atomic and molecular physics. It begins with an introduction to the field, discussing the back- groundtolowenergypositronbeams, andthencoverstopicssuchastotal scattering cross sections, elastic scattering, positronium formation, excitation and ionization, annihilation and positronium interactions. Each chapter contains a blend of theory and experiment, giving a balanced treatment of all the topics. Thebookwillbeusefulforgraduatestudentsandresearchersinphysics and chemistry. It is ideal for those wishing to gain rapid, in-depth knowledge of this unique branch of atomic physics. Michael Charlton obtained his degree and Ph.D. from University College London. In 1983 he was awarded a Royal Society University Research Fellowship, held at UCL. From 1991 to 1999 he was a Reader in Physics at UCL and was appointed to the Chair in Experimental Physics at the University of Wales, Swansea in 1999. Professor Charlton has published over one hundred research articles and written several reviews, notably for Reports on Progress in Physics and Physics Reports. John Watkin Humberston was an undergraduate at Manchester UniversityandobtainedhisPh.D.fromUniversityCollegeLondon. From 1965to1966hetaughtatTrinityCollegeDublinandbecameaLecturerat UCL in 1966, where he subsequently became Senior Lecturer, Reader and Professor. DuringthistimehehadsabbaticalleaveattheGoddardSpace Flight Center, USA, and at York University, Toronto, Canada. Professor Humberston has written numerous research articles, published mainly in Journal of Physics B, as well as several review articles in Advances in Atomic and Molecular Physics and in Physics Reports. CAMBRIDGE MONOGRAPHS ON ATOMIC, MOLECULAR AND CHEMICAL PHYSICS: 11 General editors: A. Dalgarno, P. L. Knight, F. H. Read, R. N. Zare 1. R.Schinke: Photodissociation Dynamics 2. L.Frommhold: Collision-induced Absorption in Gases 3. T.F.Gallagher: Rydberg Atoms 4. M.AuzinshandR.Ferber: Optical Polarization of Molecules 5. I.E.McCarthyandE.Weigold: Electron–Atom Collisions 6. V.Schmidt: Electron Spectrometry of Atoms using Synchrotron Radiation 7. Z.Rudzikas: Theoretical Atomic Spectroscopy 8. J.H.McGuire: Electron Correlation Dynamics in Atomic Collisions 9. J.-P.Connerade: Highly Excited Atoms 10. R.Blu¨melandW.P.Reinhardt: Chaos in Atomic Physics 11. M.CharltonandJ.W.Humberston: Positron Physics For Lucy and Bettina Positron Physics M. Charlton University of Wales Swansea J. W. Humberston University College London    Cambridge, New York, Melbourne, Madrid, Cape Town, Singapore, São Paulo Cambridge University Press The Edinburgh Building, Cambridge  , United Kingdom Published in the United States by Cambridge University Press, New York www.cambridge.org Information on this title: www.cambridge.org/9780521415507 © Cambridge University Press 2001 This book is in copyright. Subject to statutory exception and to the provision of relevant collective licensing agreements, no reproduction of any part may take place without the written permission of Cambridge University Press. First published in print format 2000 ISBN-13 978-0-511-06753-2 eBook (EBL) ISBN-10 0-511-06753-4 eBook (EBL) ISBN-13 978-0-521-41550-7 hardback ISBN-10 0-521-41550-0 hardback Cambridge University Press has no responsibility for the persistence or accuracy of s for external or third-party internet websites referred to in this book, and does not guarantee that any content on such websites is, or will remain, accurate or appropriate. Contents Preface ix 1 Introduction 1 1.1 Historical remarks 1 1.2 Basic properties of the positron and other positronic systems 3 1.3 Basic experimental techniques 11 1.4 Slow positron beams 16 1.5 The production of positronium 27 1.6 The physical basis of the interactions of positrons and positronium with atoms and molecules 35 2 Total scattering cross sections 40 2.1 Introduction 40 2.2 Theory 42 2.3 Experimental techniques 48 2.4 General discussion of systematic errors 57 2.5 Results and discussion – atoms 63 2.6 Results and discussion – molecules 81 2.7 Partitioning of the total cross section 89 3 Elastic scattering 94 3.1 Introduction 94 3.2 Theory 95 3.3 Threshold effects 132 3.4 Angle-resolved elastic scattering 139 4 Positronium formation 150 4.1 Introduction 150 4.2 Theory 151 vii viii Contents 4.3 Experimental techniques 175 4.4 Results 185 4.5 Other processes involving positronium formation 195 4.6 Comparisons with protons 200 4.7 Differential cross sections 201 4.8 Dense gases 207 5 Excitation and ionization 214 5.1 Excitation 215 5.2 Ionization – theoretical considerations 227 5.3 Ionization – experimental techniques for integrated cross sections 234 5.4 Single ionization – results 239 5.5 Multiple ionization 248 5.6 Differential cross sections 252 5.7 Inner shell ionization 259 6 Positron annihilation 264 6.1 Introduction and theoretical considerations 264 6.2 Experimental details 274 6.3 Results – positron annihilation 281 6.4 Positron drift 301 7 Positronium and its interactions 307 7.1 Fundamental studies with the positronium atom 307 7.2 Theoretical aspects of annihilation and scattering in gases 326 7.3 Experimental studies of positronium annihilation in gases 336 7.4 Slowing down 342 7.5 Bound states involving positronium 348 7.6 Studies with positronium beams 353 8 Exotic species involving positrons 362 8.1 The positronium negative ion 362 8.2 Systems containing more than one positron 368 8.3 Antihydrogen 372 Appendix: Positron conference proceedings 389 References 393 Index 449