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New Directions in Research with Third-Generation Soft X-Ray Synchrotron Radiation Sources 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 intemational board of publishers in conjunction with the NATO Scientific Affairs Division A Life Sciences Plenum Publishing Corporation B Physics London and New York C Mathematical Kluwer Academic Publishers and Physical Sciences Dordrecht, Boston and London D Behavioural and Social Sciences E Applied Sciences F Computer and Systems Sciences Springer-Verlag G Ecological Sciences Berlin, Heidelberg, New York, London, H Cell Biology Paris and Tokyo I Global Environmental Change NATO-PCO-DATA BASE The electronic index to the NATO ASI Series provides full bibliographical references (with keywords and/or abstracts) to more than 30000 contributions from international scientists published in all sections of the NATO ASI Series. Access to the NATO-PCO-DATA BASE is possible in two ways: - via online FILE 128 (NATO-PCO-DATA BASE) hosted by ESRIN, Via Galileo Galilei, 1-00044 Frascati, Italy. - via CD-ROM "NATO-PCO-DATA BASE" with user-friendly retrieval software in English, French and German (©WTV GmbH and DATAWARE Technologies Inc. 1989). The CD-ROM can be ordered through any member of the Board of Publishers or through NATO-PCO, Overijse, Belgium. Series E: Applied Sciences - Vol. 254 New Directions in Research with Third-Generation Soft X-Ray Synchrotron Radiation Sources edited by A. s. Schlachter Advanced Light Source, Lawrence Berkeley Laboratory, Berkeley, California, U.S.A. and F. J. Wuilleumier Laboratoire de Spectroscopie Atomique et lonique, Universite Paris Sud, Orsay, France Springer-Science+Business Media, B.V. Proceedings of the NATO Advanced Study Institute on New Directions in Research with Third-Generation Soft X-Ray Synchrotron Radiation Sources Maratea, Italy June 28-July 10, 1992 A C.I.P. Catalogue record for this book is available from the Library of Congress. ISBN 978-94-010-4375-5 ISBN 978-94-011-0868-3 (eBook) DOI 10.1007/978-94-011-0868-3 Printed on acid-free paper AII Rights Reserved © 1994 Springer Science+Business Media Dordrecht Originally published by Kluwer Academic Publishers in 1994 Softcover reprint of the hardcover 1 st edition No part of the material protected by this copyright notice may be reproduced or utilized in any form or by any means, electronic or mechanical, including photo- copying, recording or by any information storage and retrieval system, without written permission from the copyright owner. CONTENTS Third-Generation Synchrotron Light Sources ..................................................................... 1 A. S. Schlachter Investigation of Atomic Structure Using Synchrotron Radiation ..................................... 23 M. YaAmusia Photoionization of Atoms and Ions Using Synchrotron Radiation ................................... 47 Fran\(ois J. Wuilleumier Two-Color Experiments on Aligned Atoms ................................................................... 103 B. Sonntag and M. Pahler Two-Color Experiments in Molecules ............................................................................ 129 I. Nenner, P. Morin, M. Meyer, J. Lacoursiere, and L. Nahon Electron Correlation in Ionization and Related Coincidence Techniques ...................... 161 G. Stefani, L. Avaldi, and R. Carnilloni Soft X-Ray Emission Spectroscopy Using Synchrotron Radiation ................................ 189 Joseph Nordgren Spin Analysis and Circular Polarization ......................................................................... 203 N. V. Smith X-Ray Magnetic Circular Dichroism: Basic Concepts and Theory for 3d Transition Metal Atoms ............................................................................................. 221 J. Stohr and Y. Wu High-Resolution Soft X-Ray Absorption Spectroscopy and X-Ray Circular Dichroism ........................................................................................................................ 251 Francesco Sette Research Opportunities in Fluorescence with Third-Generation Synchrotron Radiation Sources ....................................................................................... 281 D.L. Ederer, K.E. Miyano, W.L. O'Brien, T.A. Callcott, Q.-Y. Dong, J.J. Jia, D.R. Mueller, J.-E. Rubensson, R.C.C. Perera, and R. Shuker Photoemission Spectromicroscopy ................................................................................. 299 Gelsomina DeStasio and G. Margaritondo The Properties of Undulator Radiation ........................................................................... 315 M. R. Howells and B. M. Kincaid Mirrors for Synchrotron-Radiation Beamlines ............................................................... 359 Malcolm R. Howells Index ................................................................................................................................ 387 PREFACE The NATO Advanced Study Institute (ASI) "New Directions in Research with Third-Generation Soft X-Ray Synchrotron Radiation Sources" was held on June 28-July 10, 1992, at Hotel Villa del Mare in Maratea, Italy. The Institute was sponsored by the Scientific Affairs Division of NATO, and additional support was provided by the Region of Basilicata, Italy. A total of 16 lecturers and guest lecturers and 66 participants attended. Selected from more than 120 applicants, the participants represented 18 nations of the world. Synchrotron radiation has been in use for 30 years to explore, among many other subjects, the interactions of photons with atoms. Since the pioneering experiments that demonstrated the autoionization profiles predicted by Fano in photoabsorption of the rare gases, first- and second- generation synchrotron radiation sources have been used-first in the parasitic mode and then in the dedicated mode-to systematically investigate photoionization and relaxation processes in many atomic and molecular systems. In 1975, almost twenty years ago, an early NATO Advanced Institute, "Photoionization and Other Probes of Many-Electron Interactions," was held in Carry-Ie-Rouet, France, to review the different fields in which the use of synchrotron radiation could yield some new information.1 At that time, the performance of synchrotron radiation was still rather poor: typically, 109 to 1010 photons were available in a 1% bandwidth. But progress in the field was continuous and spectacular. Many exciting discoveries were made during the following 15 years. Low-energy, third-generation synchrotron radiation sources are now being built allover the world. Two such facilities were operating by 1993-Super ACO in Orsay and the Advanced Light Source in Berkeley-and a third, ELETTRA in Trieste, is expected to open in 1994. These sources are based on storage rings with low-emittance electron or positron beams and long straight sections containing insertion devices (undulators or wigglers). As electrons pass through a linear array of permanent-magnet dipoles in an undulator, they emit photon beams characterized by extremely high brightness, partial coherence, narrow line width, and collimation in both the horizontal and vertical directions. Up to 1013 photons/s will be available in a 0.01 % bandwidth over a wide energy region, from 10 eV to about 2 keY for a 1.5-GeV storage ring. The considerable increase in brightness over radiation from other sources offers the opportunity for dramatic advances in many scientific disciplines. Thanks to the wealth of new and exciting experimental data, great progress has also been made over the last 15 years in the theoretical description of photoexcitation and photoionization processes in atoms and solids. In particular, the utility of many-body theories such as the Many- Body Perturbation Theory or Random Phase Approximation with Exchange was demonstrated. This Institute gave us the opportunity to bring together theoreticians and experimentalists to present in detail the state of the art in experiment as well as in theory, to promote discussions between experimentalists and theorists, and to suggest new directions in research using these low-energy, third-generation storage rings. An important theme of the Institute was the description of basic photoionization processes in atoms and molecules in the ground state, in excited states, and in some ionic states. Radiative and nonradiative relaxation processes following inner-shell ionization were also extensively treated. Special attention was paid to the 1 FJ. WuilIeumier, ed., Photo ionization and Other Probes of Many-electron Interactions (plenum Press, New York and London, 1976). vii viii use of circularly polarized light to study spin effects and magnetic dichroism in surfaces and interfaces. Several lecturers presented the latest developments in x-ray optics, monochromators, and undulators. They described how this advanced technology was incorporated in the design of new facilities such as the Advanced Light Source and the consequent advantages for researchers. We would like to thank the members of the Scientific Committee for contributing to the success of the Institute by proposing an excellent selection of lecturers. Special thanks are due to Professor J.P. Briand and to Ms. A. de Corte for their efficient help in managing the financial aspects of the Institute. We also thank the lecturers for preparing and delivering their presentations. Especially appreciated is the work of those who made themselves available for the two-week duration of the Institute, thus giving participants the opportunity for frequent informal and lively discussions with them. Likewise we wish to give ample credit to those lecturers who prepared manuscripts for this volume, which is, after all, the final product of the Institute. The tasks involved in organizing the Institute were extremely complex. Ms. Gloria Lawler must receive special thanks for keeping track of and communicating with applicants, participants, and lecturers prior to the Institute, and for tracking of grants. Ms. Lawler also deserves principal credit for editing, indexing, and coordinating the publication of this volume. We also wish to thank those at Lawrence Berkeley Laboratory who prepared the promotional materials for the Institute and the camera-ready manuscript for this volume: Ms. Connie Silva and Ms. Jean W olslegel for their diligent, skillful word processing of the text and Ms. Linda Geniesse for designing the ASI brochure and for her excellent enhancements of most figures herein. Ms. Geniesse with Ms. Marilee Bailey also designed the ASI poster. We would like also to acknowledge the valuable help given by Ms. Fran~oise Schont in the selection of the Institute participants. Finally, Ms. Valerie Giardini was responsible for all organizational tasks during the Institute. Everyone there appreciated her efficiency and kindness, and we are sure that all participants would join us in expressing our warmest gratitude. We wish to thank Dr. L. V. Da Cunha, Director of the NATO ASI Program, for his very helpful assistance. We also gratefully acknowledge the NATO Science Committee and the NATO Scientific Affairs Division. The financial support of NATO, as well as the help from the Region of Basilicata made it possible to invite a panel of outstanding lecturers and to provide a substantial number of grants for participants. To conclude, we wish to express our appreciation to Ms. Maria Armiento and the staff of the Hotel Villa del Mare, who contributed to making our stay highly agreeable and worthwhile, and to Ms. Barbara Kester of ITST for her assistance in arranging the Institute. Alfred S. Schlachter Fran~ois J. Wuilleumier Lawrence Berkeley Laboratory University of Paris LECTURERS Dr. M. Ya Amusia, loffe Institute, St. Petersburg, Russia Dr. G. De Stasio, CNR, Frascati, Italy Dr. M. Howells, Lawrence Berkeley Laboratory, Berkeley, California, U.S.A. Dr. B. M. Kincaid, Lawrence Berkeley Laboratory, Berkeley, California, U.S.A. Dr. G. Margaritondo, Ecole Polyt echnique Federale, Lausanne, Switzerland Dr. I. Nenner, CEN Saclay, Gif sur Yvette, France Dr. J. Nordgren, University of Uppsala, Sweden Professor Y. Petroff, University of Paris, Orsay, France Professor G. Sawatzky, University of Groningen, Groningen, The Netherlands Dr. A. S. Schlachter, Lawrence Berkeley Laboratory, Berkeley, California, U.S.A. Dr. F. Sette, European Synchrotron Radiation Facility, Grenoble, France Dr. N. Smith, AIT Bell Laboratories, Murray Hill, New Jersey, U.S.A. Professor B. Sonntag, University of Hamburg, Hamburg, Germany Dr. G. Stefani, University of Rome, Rome, Italy Dr. J. Stohr, IBM Almaden, San Jose, California, U.S.A. Professor F. Wuilleumier, University of Paris, Orsay, France SCIENTIFIC COMMITTEE Dr. A. S. Schlachter (Director), Lawrence Berkeley Laboratory, Berkeley, California, U.S.A. Professor F. Wuilleumier (Assistant Director), University of Paris, Orsay, France Professor Y. Petroff, University of Paris, Orsay, France Dr. Manfred Krause, Oak Ridge National Laboratory, Oak Ridge, Tennessee, U.S.A. Professor G. Sawatzky, University of Groningen, Groningen, The Netherlands Professor B. Sonntag, University of Hamburg, Hamburg, Germany Professor F. Yndurain, University of Madrid, Spain ix TIDRD-GENERATION SYNCHROTRON LIGHT SOURCES A.S. SCHLACHTER Lawrence Berkeley Laboratory University of California Berkeley, CA 94720 USA ABSTRACT. X rays are a powerful probe of matter because they interact with electrons in atoms, molecules, and solids. They are commonly produced by relativistic electrons or positrons stored in a synchrotron. Recent advances in technology are leading to the development of a new third generation of synchrotron radiation sources that produce vacuum-ultraviolet and x-ray beams of unprecedented brightness. These new sources are characterized by a very low electron-beam emittance and by long straight sections to accommodate permanent-magnet undulators and wigglers. Several new low-energy light sources, including the Advanced Light Source, presently under construction at the Lawrence Berkeley Laboratory, and ELETTRA, presently being constructed in Trieste, will deliver the world's brightest synchrotron radiation in the VUV and soft x-ray regions of the spectrum. Applications include atomic and molecular physics and chemistry, surface and materials science, microscopy, and life sciences. 1. Introduction Light is one of the most important tools of science. It is the key to viewing the universe-from distant galaxies to cells, molecules, and even atoms. Light has a dual nature, behaving both as a stream of massless particles (photons) and as electromagnetic waves moving through space. Visible light, which enables us to see the everyday objects around us, is easily generated and easy to detect. The sun, electric lamps, and fire produce it. We can see visible light with our eyes and detect it with photographic film; however, it constitutes only a tiny fraction of the full electromagnetic spectrum (see Fig. 1). The remainder of the spectrum consists of light with wavelengths longer or shorter than those of visible light. On the longer side are radio waves, microwaves, and infrared radiation. Shorter- wavelength light includes ultraviolet, x rays, and gamma rays. These regions of the spectrum are invisible to the eye and must be detected by special means. Each region has a characteristic range of wavelengths and photon energies that determine the degree to which the light will penetrate and interact with matter. Light sources relevant to this institute produce radiation in the vacuum- ultraviolet and soft x-ray regions of the spectrum. This light is useful for several reasons: • It can penetrate materials opaque to visible light (see Fig. 2). • It has the right wavelengths-from about 10-7 to 10-10 meter-for exploring the atomic structure of solids, molecules, and important biological structures. The sizes of atoms, molecules, and proteins as well as the lengths of chemical bonds and the minimum distances between atomic planes in crystals are in this range (see Fig. 3). High-resolution x-ray microscopy is one technique used for such exploration. The combination of wavelengths shorter than visible light and the possibility of obtaining contrast through the A.S. Schlachter and F.J. Wuilleumier (eds), New Directions in Research with Third-Generation Soft X-Ray Synchrotron Radiation Sources, 1-22. © 1994 All Rights Reserved. 2 RADIATION SOURCES RTAYDPIEA TOIOFN DEOTBEJCETCATBSL E 1O-9 t- - 103 / H+- / 10-7 ~ - 101 ~House RadIo antenna \ Q '. \ 10-5 - 13 ~ - 10-1 B~asebal l o }o K:lys=tro=n :~ 1. .-.. 10--3 ~ I 0w - 10--3 0;- ~Bee L~ameps aend laiS~ers ./ \ / ~ 10-1 -~C:JI ~IaE; 10-5 I.a<;: ~Cel ~\ E;j w Ii; f V0iru s ~ Synchrotron- ,I / ~8~ 101 r- ir:~n; : ~.:..>.. 10-7~ P,ro.te in rad . lton sources \ 1()3 1- '" 10-9 ~ Molecule P"\'- \ . ~ i ~ ~ X·ray lubes "~~ lOS r- 0x - 10-11 Atom WFigiluhrel m2. TCh. isR iomeangteg ewna, s wmhaod e dinis c1o8v9e6r beyd ~ Nu~cle us x rays and put them to practical use. (From RadIOa.c•ti.ve. so urces ~/ ~~/ .. ~~ 107 r- i - 10-13 PrO0 lon EOa. rGlyl aHssisetro, rWy oil/htehlem R Coeonntrgaedn RRoaeynst,g 1e9n3, 4T.)h e 8> ~ Panicle accelerators \\\ 109 nl - 10-15 Quarks (1) (f---0---O Figure 1. The electromagnetic spectrum covers a wide J 6---0---0': range of wavelengths and photon energies. (From ~O--.Q---0: I " 1S9y87n cbhyr oStcrioenn tRifiacd Aiamtioenri,c"a nb,y I nHc. WAliln riicgkh.t s rCeosepryvreidg.h) t © X I I 1I ,UI, v. 6I -0---0---6/: I " I t 10 Atom l: : :p' 0---0---0 Crystal 0---0 -./ x ~ x = a few angstroms Chemical bond Figure 3. Atoms, chemical bonds, and the distances between atomic planes in crystals all measure a few angstroms- corresponding to the wavelengths of light in the x-ray energy range.
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