Methods of Experimental Physics VOLUME 17 ATOMIC PHYSICS: ACCELERATORS METHODS OF EXPERIMENTAL PHYSICS: L. Marton and C. Marton, Editors-in-Chief Volume 17 ATOMIC PHYSICS Accelerators Edited by PATRICK RICHARD Department of Physics Kansas State University Manhattan, Kansas @ I980 ACADEMIC PRESS A Subsidiary of Horcourt Brace jovanovich, Publishers New York London Toronto Sydney San Francisco COPYRIGH@T 1 980, BY ACADEMICPR ESS,IN C. ALL RIGHTS RESERVED. NO PART OF THIS PUBLICATION MAY BE REPRODUCED OR TRANSMITTED IN ANY FORM OR BY ANY MEANS, ELECTRONIC OR MECHANICAL, INCLUDING PHOTOCOPY, RECORDING, OR ANY INFORMATION STORAGE AND RETRIEVAL SYSTEM, WITHOUT PERMISSION IN WRITING FROM THE PUBLISHER. ACADEMIC PRESS, INC. 11 1 Fifth Avenue, New York, New York 10003 United Kingdom Edition published by ACADEMIC PRESS, INC. (LONDON) LTD. 24/28 Oval Road, London NWl 7DX Library of Congress Cataloging in Publication Data Main entry under title: Atomic physics: Accelerators (Methods in experimental physics ; v. 17) Includes bibliographical references and index. 1. Collisions (Nuclear physics)--Addresses, essays, lectures. 2. Ion bombardment--Addresses, essays, lectures. I. Marton, Ladislaus Laszlo. 11. Marton, C. 111. Richard, Patrick, Date IV. Series. QC794.6 .C6 A25 539 .7’3 80- 15602 ISBN 0-12-475959-9 (v. 17) PRINTED IN THE UNITED STATES OF AMERICA 80 81 82 83 9 8 7 6 5 4 3 2 1 This work is dedicated to the memory of James R. Macdonald, whose career was devoted to the study ojatomic collisions. Jim made many valuable contributions through his diligent and uncompromising search for correct solutions to atomic problems. Probably his last written con- tribution to science is contained in this volume. He did not see a printed version of his contribution. This Page Intentionally Left Blank CONTENTS CONTRIBUTOR.S . . . . . . . . . . . . . . . . . . . . . . xvii FORWE ORD . . . . . . . . . . . . . . . . . . . . . . . . . xix PREFACE... . . . . . . . . . . . . . . . . . . . . . . . xxi VOLUMESIN SERIES.. . . . . . . . . . . . . . . , . . . . xxiii 1. Introduction by PATRICKR ICHARD 1.1. Atomic Collisions with Accelerated Ions . . . . . . . . 1 1.2. Accelerated Ions for Atomic Collisions . . . . . . . . 3 1.2.1. Impetus from Nuclear Physics for Accelerated Ions . . . . . . . . . . . . . . . . . . . 3 1.2.2. The Accelerated-Ion Method . . . . . . . . 4 1.2.3. Use of Accelerated Ions for Atomic Collisions . 20 2. Energy Loss of High-Velocity Ions in Matter by WEI-KANC HU 2.1. Introduction . . . . . . . . . . . . . . . . . . . . 25 2.2. General Concepts of Energy Loss . . . . . . . . . . 26 2: .3. Energy Loss Theories: General Background. . . . . . 30 2.3.1. Coulomb Scattering and Energy Loss . . . . . 3 1 2.3.2. Perturbation Method and Dielectric Description. 33 2.3.3. Bethe Formula . . . . . . . . . . . . . . . 34 2.3.4. Mean Excitation and Ionization Energy I. . . . 35 vii viii CONTENTS 2.3.5. Shell Correction . . . . . . . . . . . . . . . 36 2.3.6. Dependence of Energy Loss on Z1 . . . . . . 37 2.3.7. Low-Velocity Electronic Energy Loss . . . . . 39 2.3.8. Nuclear Energy Loss . . . . . . . . . . . . 41 2.3.9. Electronic Energy Loss in the Medium-Velocity Region . . . . . . . . . . . 45 2.4. Experimental Methods on Energy Loss . . . . . . . . 46 2.4.1. Transmission Measurements on Thin Foils . . . 47 2.4.2. Transmission Measurements on Gaseous Targets 51 2.4.3. Transmission Measurements on Supported Films 53 2.4.4. Transmission Measurements on a Thin Layer on a Solid-state Detector . . . . . . . . . . . . 54 2.4.5. Backscattering Energy Loss . . . . . . . . . 58 2.4.6. Backscattering Thick-Target Yield . . . . . . . 61 2.4.7. Measurement of Energy Loss by the Inverted Doppler Shift Attenuation (IDSA) Method . . . 65 2 .5 . Current Problems in Stopping Cross Sections . . . . . 68 2.5.1. Chemical Effect: Bragg’s Rule . . . . . . . . 69 . . . . . . . . . . . . . . 2.5.2. Solid-state Effect 69 2.5.3. Structure Effect . . . . . . . . . . . . . . . 70 2.5.4. Energy Straggling . . . . . . . . . . . . . . 70 2.5.5. Charge State of the Projectiles . . . . . . . . 71 2.5.6. The Barkas Effect . . . . . . . . . . . . . . 71 2.5.7. Ion Clusters Effect . . . . . . . . . . . . . 71 . . . . . . . . . . . . 2.5.8. Nuclear Energy Loss 72 3 . Charge Equilibration of High-Velocity Ions in Matter by HANSD . BETZ . . . . . . . . . . . . . . . . . . . 3.1. Introduction 73 3.1.1. Historic Background . . . . . . . . . . . . . 73 3.1.2. Present Situation . . . . . . . . . . . . . . 74 . . . . . 3.1.3. Review Articles and Data Collections 76 3.2. Fundamental Charge Exchange Processes . . . . . . . 78 3.2.1. Definitions and Basic Processes . . . . . . . . 78 3.2.2. Mathematical Description of Charge-State Fractions under Nonequilibrium and Equilibrium Conditions . . . . . . . . . . . . 80 CONTENTS ix 3.3. Experimental Techniques and Data Analysis . . . . . . 83 3.3.1. Measurement of Charge-State Fractions . . . . 83 3.3.2. Auxiliary Methods . . . . . . . . . . . . . . 87 3.4. Electron Capture . . . . . . . . . . . . . . . . . . 89 3.4.1. Theory of Electron Capture in Simple Collision Systems . . . . . . . . . . . . . . . . . . 89 3.4.2. Electron Capture in Complex Systems . . . . . 94 3.4.3. Experimental Results on Electron Capture Cross Sections . . . . . . . . . . . . . . . . . . 97 3.4.4. Multiple Electron Capture . . . . . . . . . . 104 . . . 3.4.5. Very Large Charge Exchange Probabilities 108 . . . . 3.4.6. Capture into Very High Quantum States 108 3.4.7. Capture into Continuum States . . . . . . . . 109 3.5. Electron Loss . . . . . . . . . . . . . . . . . . . 110 3.5.1. Target Ionization Due to Light Particles . . . . 110 3.5.2. Projectile Ionization . . . . . . . . . . . . . 113 3.5.3. Experimental Results on Electron Loss Cross Sections . . . . . . . . . . . . . . . . . . 114 3.5.4. Multiple-Electron Loss . . . . . . . . . . . . 116 3.5.5. Small-Impact-Parameter Collisions and Multiple- Electron Loss . . . . . . . . . . . . . . . . 117 3.6. Equilibrium Charge-State Distributions . . . . . . . . 118 3.6.1. Experimental Results . . . . . . . . . . . . 118 3.6.2. Semiempirical Descriptions of Equilibrium Charge-State Distributions . . . . . . . . . . 122 3.7. Average Equilibrium Charge States . . . . . . . . . . 125 3.7.1. On the Lamb-Bohr (LB) Criterion . . . . . . 125 3.7.2. Experimental Average Equilibrium Charge States 127 3.7.3. Semiempirical Relationships for the Average Equilibrium Charge . . . . . . . . . . . . . 129 3.8. Density Effects and Excited States . . . . . . . . . . 131 3.8.1. Density Effect in Gaseous Targets . . . . . . . 131 3.8.2. Density Effect in Solid Targets . . . . . . . . 134