Physics of Atoms and Molecules – serie

The papers collected in this volume have been presented during a workshop on "Electron-Atom and Molecule Collisions" held at the Centre for Interdisciplinary Studies of the University of Bielefeld in May 1980. This workshop, part of a larger program concerned with the "Properties and Reactions of Isolated Molecules and Atoms," focused on the theory and computational techniques for the quanti­ tative description of electron scattering phenomena. With the advances which have been made in the accurate quantum mechanical characterisation of bound states of atoms and molecules, the more complicated description of the unbound systems and resonances important in electron collision processes has matured too. As expli­ cated in detail in the articles of this volume, the theory for the quantitative explanation of elastic and inelastic electron molecule collisions, of photo- and multiple photon ionization and even for electron impact ionization is well developed in a form which lends itself to a complete quantitative ab initio interpretation and pre­ diction of the observable effects. Many of the experiences gained and the techniques which have evolved over the years in the com­ putational characterization of bound states have become an essential basis for this development. To be sure, much needs to be done before we have a complete and detailed theoretical understanding of the known collisional processes and of the phenomena and effects, which may still be un­ covered with the continuing refinement of the experimental tech­ niques.

Scattering phenomena play an important role in modern physics. Many significant discoveries have been made through collision experiments. Amongst diverse kinds of collision systems, this book sheds light on the collision of an electron with a molecule. The electron-molecule collision provides a basic scattering problem. It is scattering by a nonspherical, multicentered composite particle with its centers having degrees of freedom of motion. The molecule can even disintegrate, Le., dissociate or ionize into fragments, some or all of which may also be molecules. Although it is a difficult problem, the recent theoretical, experimental, and computational progress has been so significant as to warrant publication of a book that specializes in this field. The progress owes partly to technical develop­ ments in measurements and computations. No less important has been the great and continuing stimulus from such fields of application as astrophysics, the physics of the earth's upper atmosphere, laser physics, radiation physics, the physics of gas discharges, magnetohydrodynamic power generation, and so on. This book aims at introducing the reader to the problem of electron­ molecule collisions, elucidating the physics behind the phenomena, and review­ ing, to some extent, up-to-date important results. This book should be appropri­ ate for graduate reading in physics and chemistry. We also believe that investi­ gators in atomic and molecular physics will benefit much from this book.

Atomic and nuclear physics are two flourishing but distinct branches of physics; the subject of isotope shifts in atomic spectra is one of the few that links these two branches. It is a subject that has been studied for well over fifty years, but interest in the subject, far from flagging, has been stimulated in recent years. Fast computers have enabled theoreticians to evaluate the properties of many-electron atoms, and laser spectroscopy has made it possible to measure isotope shifts in the previously unmeasurable areas of very rare isotopes, short-lived radioactive isotopes, weak transitions, and transitions involving high-lying atomic levels. Isotope shifts can now be measured with greater accuracy than before in both optical transitions and x-ray transitions of muonic atoms; this improved accuracy is revealing new facets of the subject. I am very grateful to Dr. H. G. Kuhn, F. R. S. , for having introduced me to the subject in the 1950s, and for supervising my efforts to measure isotope shifts in the spectrum of ruthenium. I thus approach the subject as an experimental atomic spectroscopist. This bias is obviously apparent in my use of the spectroscopist's notation of lower-upper for a transition, rather than the nuclear physicist's upper-lower. My reasons are given in Section 1. 3 and I hope that nuclear physicists will forgive me for using this notation even for muonic x-ray transitions.

My aim in this book has been to give an account of the theoretical methods of analysis of multiphoton processes in atomic physics. In this account I have emphasized systematic methods as opposed to ad hoc approaches. Both perturbative and nonperturbative methods are presented with il- lustrative results of concrete applications. The perturbation theory is the primary tool of analysis of nonresonant multiphoton processes. It is developed here in conjunction with a diagrammatic language and is also renormalized to free it from the unwanted divergences which accompany the ordinary treatment when higher-order corrections are considered. The nonperturbative methods (i.e., methods other than that of power series ex- pansion in the field strength) become particularly important for consistent treatments of problems involving, for example, intermediate resonances, high field strengths, and finite pulse duration. The specifically nonpertur- bative methods for multiphoton transitions are presented in Chapters 6-11. The methods of resolvent equations and of effective Hamiltonians are developed for both the stationary and the time-dependent fields.The densi- ty matrix method is presented in conjunction with the problems of relaxa- tion and of fluctuating fields. The Floquet theory is presented both in the energy domain and in the time domain. Also treated are the methods of continued fractions, recursive iterative equations, and chain Hamiltonians.

This book is devoted to the investigation of a rather prevalent process in nature: interaction of atoms with electromagnetic radiation. Primary attention is given to the low and intermediate photon energy region, from tens to hundreds of electron-volts. It is in this region that the probability of photon absorption and photoionization is largest. Data in this energy region are very interesting and useful in astrophysics and plasma physics, solid-state physics and quantum electronics, and in a number of other branches of science and technical applications. Formulae for hydrogen atom photoionization are given in almost all textbooks on quantum mechanics. Together with the limited amounts of experimental data available up to the beginning of the sixties, the formulae gave an impression of the completeness of the study of photoionization, of the absolute clarity of the mechanism of the process, and of the possibility of calculating rather easily its probability using the formulae.

Covering both theory and applications, this important work provides a comprehensive introduction to the modern theory of X-ray and electronic spectra of free atoms. Romas Karazija discusses methods of angular momenta, irreducible tensorial operators, and coefficients of fractional parentage and their use in determining cross sections and probabilities of elementary processes. In addition, Karazija addresses the structure of electronic shells with inner vacancies and many-body effects.

In response to the explosion of theories and experiments since the appearance of the first edition, the author has revised and expanded his basic text. New sections include up-to-date discussions of multiphoton ionization, and electron-atom and atom-atom scattering in laser fields, reaffirming the work's position as the standard introduction to the field.

The authors aim to hone the theory of electron-atom and electron-ion collisions by developing mathematical equations and comparing their results to the wealth of recent experimental data. This first of three parts focuses on potential scattering, and will serve as an introduction to many of the concepts covered in Parts II and III. As these processes occur in so many of the physical sciences, researchers in astrophysics, atmospheric physics, plasma physics, and laser physics will all benefit from the monograph.

This volume contains the invited papers and selected contributed papers presented at the biennial International Symposium on ELECTRON COLLISIONS WITH MOLECULES, CLUSTERS AND SURF ACES held at Royal Holloway, University of London from 29th to 30th July, 1993. This Symposium was a Satellite Meeting of the XVIII International Conference on the Physics of Electronic and Atomic Collisions (ICPEAC) and follows a 16 year tradition of Satellite Conferences in related areas of collisions held in association with previous ICPEAC's. In the past each of these electron -molecule symposia covered the broad field of electron-molecule scattering at rather low energies, but also included hot topics. This time as well as covering the whole field, well defined electron collisions with clusters and with particles in the complex potential of a surface were emphasized. Not many details are known about such collisions, although they become more and more important in surface characterisation, plasma-wall interactions, electron induced desorption and reorganisation of adsorbed particles. Recently, much work, theoretical and experimental, has been devoted to electron collisions with rather large carbon, silicon and halogen containing molecules. These problems are of relevance in plasma assisted thin film formation and etching of surfaces and can now be approached with advanced theoretical methods and experimental equipment.

The EPSRC (Engineering and Physical Science Research Committee of the U. K. ) suggested two Workshops (York University, 22-23 September, 1993 and 15-16 April, 1994) for possible development of polarized electron/photon physics as targeted areas of research. The remit of these meetings included identifying research groups and their activities in polarized electron/polarized photon physics, listing relevant existing facilities (particularly electron spin sources and polarimeters), possible joint projects between research groups in the U. K. , recognizing future needs of projects for research of the highest scientific merit and referring to international comparisons of these research activities. Although very diverse but interconnected, the areas of research presented at the Workshops embrace atomic, molecular, surface, and solid state physics. In more detail these areas covered: electron spin correlations and photon polarization correlations in atomic and molecular collisions and photoionization, electron spin effects in scanning tunneling microscopy, surface and interface magnetism from X-ray scattering and polarized Auger electrons (including analysis of domain structures in solids and surfaces), polarized electrons from multiphoton ionization, quasi-atomic effects in solid state physics, dichroism in molecular and surface processes, Faraday rotation and high-field magneto-optics and polarization effects in simultaneous higher order electron-photon excitations. It is obvious from the spectrum of research fields presented at the Workshops that physicists of primarily two communities, namely those studying electron and photon spin interactions with gaseous atomic and molecular targets and those using condensed matter targets for their studies, interacted very closely witheach other.

A uniquely practical book, this monograph is the first to describe basic and applied spectroscopic techniques for the study of physical processes in high frequency, electrodeless discharge lamps. Special attention is given to the construction and optimization of these lamps, a popular source of line spectra and an important tool in ultraprecise optical engineering. Highlights include discussions of: high precision measurements of gas pressures spectral source lifespan and more.

The great advantage of coincidence measurements is that by suitable choice of the kinematical and geometrical arrangement one may probe delicate physical effects which would be swamped in less differential experiments. The measurement of the triple dif­ ferential and higher-order cross sections presents enormous technical difficulties, but refined experiments of this type provide an insight into the subtleties of the scattering process and offer a welcome, if severe, test of the available theoretical models. The last few years have been an exciting time to work in the field and much has been learned. Profound insights have been gleaned into the basic Coulomb few body problem in atomic physics: the experimental study of the fundamental (e,2e) processes on hydrogen and helium targets continues to add to our knowledge and indeed to challenge the best of our theoretical models; significant advances have been made in the understanding of the "double excitation problem," that is the study of ionization processes with two active target electrons: important measurements of (e,3e), (,),,2e), excitation-ionization and excitation autoionization have been reported and strides have been made in their theoretical description; the longstanding discrepancies between theory and experiment for relativistic (e,2e) processes were resolved, spin dependent effects predicted and ob­ served and the first successful coincidence experiments on surfaces and thin films were announced. Theory and experiment have advanced in close consort. The papers pre­ sented here cover the whole gambit of research in the field. Much has been achieved but much remains to be done.

Research on photon and electron collisions with atomic and molecular targets and their ions has seen a rapid increase in interest, both experimentally and theoretically, in recent years. This is partly because these processes provide an ideal means of investigating the dynamics of many particle systems at a fundamental level and partly because their detailed understanding is required in many other fields, particularly astrophysics, plasma physics and controlled thermonuclear fusion, laser physics, atmospheric processes, isotope separation, radiation physics and chemistry and surface science. In recent years a number of important advances have been made, both on the experimental side and on the theoretical side. On the experimental side these include absolute measurements of cross sections, experiments using coincidence techniques, the use of polarised beams and targets, the development of very high energy resolution electron beams, the use of synchrotron radiation sources and ion storage rings, the study of laser assisted atomic collisions, the interaction of super-intense lasers with atoms and molecules and the increasing number of studies using positron beams.

This book arises from the significant quantity of original results in the field of impact spectropolarimetry, mainly for solar flare studies, and the evident potential applications of this technique to environmental physics, astrophysics, and hot plasma. This is a practically oriented book, describing theoretical fundamentals and implementation of this new interdisciplinary remote sensing technique. A basic phenomenon for impact spectropolarimetric sensing is the polarization ofthe electron shells of an ensemble of free atomic particles (atoms, ions, molecules) due to collisional interaction. Slow collisions in the presence of internal anisotropies in the relative velocity space inside any ionized medium, as well as bombardment of a diluted gas by fast precipitating light projectiles, are analyzed in detail as principal impact polarization mechanisms. Impact spectro­ polarimetric sensing incorporates state-of-the-art theoretical methods of colli­ sional physics in combination with reliable polarimetric measurements. This technique is illustrated by the new quantitative sensing of energy transport to the upper region of the chromosphere during solar flares, making use of ground­ based solar spectropolarimetric observations. Apart from general astrophysical and solar-terrestrial significance, a solar flare, the brightest nonthermal phenomenon, is a good candidate for the demonstration of new opportunities of impact spectropolarimetry. New astrophysical achievements of quantitative spectropolarimetry are particularly considered in this book. The theoretical part presents a quantum mechanical description of impact polarization and the spectropolarimetric manifestations for different energies of the colliding partners.

Electron Momentum Spectroscopy measures the energy-momentum density of the electrons in atoms, molecules and solids by means of a kinematically-complete ionization reaction initiated by an electron beam. The construction of spectrometers and the acquisition and reduction of cross-section data are described in detail. The quantum theory of the reaction is explained and the experimental verification is given. It is shown how to extract quasiparticle orbitals, and coefficients describing electron correlations of the data. These quantities are derived from the many-body theory of the electronic structure of atoms, molecules and solids. The relationship to less complete methods of investigating electronic structure is discussed. Examples are given of the determination of atomic and molecular orbitals and quantities relating them to the observed states of the residual ion. For amorphous, polycrystalline and crystalline solids and surfaces, examples show the energy-momentum density of valence electron bands, and effects due to electron diffraction and plasmon excitation. The book aims to give a complete account of electron momentum spectroscopy to date. Its significance is that it is a sensitive and experimentally-verifiable test of essentially every aspect of calculations of electronic structure. It is the only such probe available.

The last few years have seen some remarkable advances in the understanding of atomic phenomena. It is now possible to isolate atomic systems in traps, measure in coincidence the fragments of collision processes, routinely produce, and study multicharged ions. One can look at bulk matter in such a way that the fundamental atomic character is clearly evident and work has begun to tease out the properties of anti­ matter. The papers in this book reflect many aspects of modem Atomic Physics. They correspond to the invited talks at a conference dedicated to the study of "New Directions in Atomic Physics," which took place in Magdalene College, Cambridge in July of 1998. The meeting was designed as a way of taking stock of what has been achieved and, it was hoped, as a means of stimulating new research in new areas, along new lines. Consequently, an effort was made to touch on as many directions as we could in the four days of the meeting. We included some talks which overviewed whole subfields, as well as quite a large number of research contributions. There is a unity to Physics and we tried to avoid any artificial division between theory and experiment. We had roughly the same number of talks from those who are primarily concerned with making measurements, and from those who spend their lives trying to develop the theory to describe the experiments.

This collection of 18 scientific papers sets out developments in the scientific disciplines and endeavours to which Professor P.G. Burke has contributed over the last 40 years, prior to his formal retirement in September 1998. The aim of the volume is to provide a survey of the developments in many areas of atomic and molecular collision physics and applications and also a number of scientific disciplines where supercomputers play a central role. It will be of use to researchers in various scientific areas and especially to those entering new areas of atomic, molecular and optical physics. The book will form a permanent record celebrating the many contributions by Professor P.G. Burke CBE FRS to the advancement of scientific knowledge.

Polarization and Correlation Phenomena in Atomic Collisions: A Practical Theory Course bridges the gap between traditional courses in quantum mechanics and practical investigations. The authors' goal is to guide students in training their ability to perform theoretical calculations of polarization and correlation characteristics of various processes in atomic collisions. The book provides a concise description of the density matrix and statistical tensor formalism and presents a general approach to the description of angular correlation and polarization phenomena. It illustrates an application of the angular momentum technique to a broad variety of atomic processes. The book contains derivations of the most important expressions for observable quantities in electron-atom and ion-atom scattering, including that for polarized beams and/or polarized targets, in photo-induced processes, autoionization and cascades of atomic transitions. Spin-polarization and angular distributions of the reaction products are described, including the angular correlations in different types of coincidence measurements. The considered processes exemplify the general approach and the number of examples can be easily extended by a reader. The book supplies researchers, both theoreticians and experimentalists with a collection of helpful formulae and tables, and can serve as a reference book. Based on a highly regarded course at Moscow State University and elsewhere, the book provides real guidance on theoretical calculations of practical use.

The Hans Kleinpoppen Symposium on "Complete Scattering Experiments" th was held in honor of Hans Kleinpoppen’s 70 birthday. It took place in Il Ciocco, Italy. The symposium had two purposes: to present the work that Hans Kleinpoppen has done or initiated during his remarkable scientific career, and to bring people from various fields together who perform complete scattering experiments. Hans Kleinpoppen’s work included electron and photon impact experiments which were accompanied by studies of entangled states - a field of high current interest. Representatives from each of these fields gave excellent lectures on their particular subjects, and many discussions that started during the sessions were continued later in the relaxed atmosphere of the Il Ciocco resort. The breathtaking view of the beautiful landscape will be an unforg- table memory to all who participated in this extraordinary scientific event. The coherent and ideal combination of subject, people and location reflected the coherence of Hans Kleinpoppen’s aims and activities in science and life. We offer our grateful thanks to all contributers who made this volume such a worthy tribute to Hans Kleinpoppen. We also like to thank Rainer Hentges for the painstaking work to prepare this volume in its complete ready to print version. We are also grateful to the Royal Society of London and the Max– Planck–Gesellschaft who generous support of the Hans Kleinpoppen sym- sium made this marvelous meeting and this proceedings possible.

An understanding of the collisions between micro-particles is of great importance for the number of fields belonging to physics, chemistry, astrophysics, biophysics and so forth. In this work a theory for electron-atom and molecule collisions is developed using non-relativistic quantum mechanics in a systematic manner. The scattering theory is an essential part of the quantum mechanics course of all universities. During the last 30 years, the author has lectured on the topics presented in this book (collisions physics, photon-atom collisions, electron-atom and electron-molecule collisions, "electron-photon delayed coincidence technique"etc.)

This volume deals with the basic knowledge and understanding of fundamental interactions of low energy electrons with molecules. It pro­ vides an up-to-date and comprehensive account of the fundamental in­ teractions of low-energy electrons with molecules of current interest in modern technology, especially the semiconductor industry. The primary electron-molecule interaction processes of elastic and in­ elastic electron scattering, electron-impact ionization, electron-impact dissociation, and electron attachment are discussed, and state-of-the­ art authoritative data on the cross sections of these processes as well as on rate and transport coefficients are provided. This fundamental knowledge has been obtained by us over the last eight years through a critical review and comprehensive assessment of "all" available data on low-energy electron collisions with plasma processing gases which we conducted at the National Institute of Standards and Technology (NIST). Data from this work were originally published in the Journal of Physical and Chemical Reference Data, and have been updated and expanded here. The fundamental electron-molecule interaction processes are discussed in Chapter 1. The cross sections and rate coefficients most often used to describe these interactions are defined in Chapter 2, where some recent advances in the methods employed for their measurement or calculation are outlined. The methodology we adopted for the critical evaluation, synthesis, and assessment of the existing data is described in Chapter 3. The critically assessed data and recommended or suggested cross sections and rate and transport coefficients for ten plasma etching gases are presented and discussed in Chapters 4, 5, and 6.

There is a unity to physics; it is a discipline which provides the most fundamental understanding of the dynamics of matter and energy. To understand anything about a physical system you have to interact with it and one of the best ways to learn something is to use electrons as probes. This book is the result of a meeting, which took place in Magdalene College Cambridge in December 2001. Atomic, nuclear, cluster, soHd state, chemical and even bio- physicists got together to consider scattering electrons to explore matter in all its forms. Theory and experiment were represented in about equal measure. It was meeting marked by the most lively of discussions and the free exchange of ideas. We all learnt a lot. The Editors are grateful to EPSRC through its Collaborative Computational Project program (CCP2), lOPP, the Division of Atomic, Molecular, Optical and Plasma Physics (DAMOPP) and the Atomic Molecular Interactions group (AMIG) of the Institute of Physics for financial support. The smooth running of the meeting was enormously facilitated by the efficiency and helpfulness of the staff of Magdalene College, for which we are extremely grateful. This meeting marked the end for one of us (CTW) of a ten-year period as a fellow of the College and he would like to take this opportunity to thank the fellows and staff for the privilege of working with them.

Quantum mechanics has been mostly concerned with those states of systems that are represented by state vectors. In many cases, however, the system of interest is incompletely determined; for example, it may have no more than a certain probability of being in the precisely defined dynamical state characterized by a state vector. Because of this incomplete knowledge, a need for statistical averaging arises in the same sense as in classical physics. The density matrix was introduced by J. von Neumann in 1927 to describe statistical concepts in quantum mechanics. The main virtue of the density matrix is its analytical power in the construction of general formulas and in the proof of general theorems. The evaluation of averages and probabilities of the physical quantities characterizing a given system is extremely cumbersome without the use of density matrix techniques. The representation of quantum mechanical states by density matrices enables the maximum information available on the system to be expressed in a compact manner and hence avoids the introduction of unnecessary variables. The use of density matrix methods also has the advan­ tage of providing a uniform treatment of all quantum mechanical states, whether they are completely or incompletely known. Until recently the use of the density matrix method has been mainly restricted to statistical physics. In recent years, however, the application of the density matrix has been gaining more and more importance in many other fields of physics.

A uniquely practical book, this monograph is the first to describe basic and applied spectroscopic techniques for the study of physical processes in high frequency, electrodeless discharge lamps. Special attention is given to the construction and optimization of these lamps, a popular source of line spectra and an important tool in ultraprecise optical engineering. Highlights include discussions of: high precision measurements of gas pressures spectral source lifespan and more.

Polarization and Correlation Phenomena in Atomic Collisions: A Practical Theory Course bridges the gap between traditional courses in quantum mechanics and practical investigations. The authors' goal is to guide students in training their ability to perform theoretical calculations of polarization and correlation characteristics of various processes in atomic collisions. The book provides a concise description of the density matrix and statistical tensor formalism and presents a general approach to the description of angular correlation and polarization phenomena. It illustrates an application of the angular momentum technique to a broad variety of atomic processes. The book contains derivations of the most important expressions for observable quantities in electron-atom and ion-atom scattering, including that for polarized beams and/or polarized targets, in photo-induced processes, autoionization and cascades of atomic transitions. Spin-polarization and angular distributions of the reaction products are described, including the angular correlations in different types of coincidence measurements. The considered processes exemplify the general approach and the number of examples can be easily extended by a reader. The book supplies researchers, both theoreticians and experimentalists with a collection of helpful formulae and tables, and can serve as a reference book. Based on a highly regarded course at Moscow State University and elsewhere, the book provides real guidance on theoretical calculations of practical use.

The Hans Kleinpoppen Symposium on "Complete Scattering Experiments" th was held in honor of Hans Kleinpoppen’s 70 birthday. It took place in Il Ciocco, Italy. The symposium had two purposes: to present the work that Hans Kleinpoppen has done or initiated during his remarkable scientific career, and to bring people from various fields together who perform complete scattering experiments. Hans Kleinpoppen’s work included electron and photon impact experiments which were accompanied by studies of entangled states - a field of high current interest. Representatives from each of these fields gave excellent lectures on their particular subjects, and many discussions that started during the sessions were continued later in the relaxed atmosphere of the Il Ciocco resort. The breathtaking view of the beautiful landscape will be an unforg- table memory to all who participated in this extraordinary scientific event. The coherent and ideal combination of subject, people and location reflected the coherence of Hans Kleinpoppen’s aims and activities in science and life. We offer our grateful thanks to all contributers who made this volume such a worthy tribute to Hans Kleinpoppen. We also like to thank Rainer Hentges for the painstaking work to prepare this volume in its complete ready to print version. We are also grateful to the Royal Society of London and the Max– Planck–Gesellschaft who generous support of the Hans Kleinpoppen sym- sium made this marvelous meeting and this proceedings possible.

There is a unity to physics; it is a discipline which provides the most fundamental understanding of the dynamics of matter and energy. To understand anything about a physical system you have to interact with it and one of the best ways to learn something is to use electrons as probes. This book is the result of a meeting, which took place in Magdalene College Cambridge in December 2001. Atomic, nuclear, cluster, soHd state, chemical and even bio- physicists got together to consider scattering electrons to explore matter in all its forms. Theory and experiment were represented in about equal measure. It was meeting marked by the most lively of discussions and the free exchange of ideas. We all learnt a lot. The Editors are grateful to EPSRC through its Collaborative Computational Project program (CCP2), lOPP, the Division of Atomic, Molecular, Optical and Plasma Physics (DAMOPP) and the Atomic Molecular Interactions group (AMIG) of the Institute of Physics for financial support. The smooth running of the meeting was enormously facilitated by the efficiency and helpfulness of the staff of Magdalene College, for which we are extremely grateful. This meeting marked the end for one of us (CTW) of a ten-year period as a fellow of the College and he would like to take this opportunity to thank the fellows and staff for the privilege of working with them.

Like a river, the progress of science has a tendency to run tast or slow. Once the water meets a dam, it may stop for a while, but eventually it will flow over the top and run fast again. In scientific research, a breakthrough to overcome a simile>r barrier is often made by a small number of scientists, or perhaps by a single person of special creativity, extraordinary talent and unusual perseverance. Through such individuals science can proceed in great strides. No one can deny that Professor Kazuo Takayanagi is one of these special individuals who have played a leading role in the field of atomic and molecular physics, as well as space physics. This book is dedicated to Professor Takayanagi on the occasion of his retirement from the Institute of Space and Astronautical Science. Professor Takayanagi was born in 1926 and grew up in Tomakomai in Hokkaido, the northern island of Japan. In his boyhood, he was interested in natural sciences, particularly astronomy. On 5th February, 1943, when he was attending secondary school, a solar eclipse was seen in his town. He organized a group of students from his school to observe the eclipse. He still remembers the scene: it grew so dark during the eclipse that two stars, Vega and Arcturus, could be seen. After graduation from the University of Tokyo in 1948, he entered the graduate school there.