Readers intent on mastering the basics should start by reading the first few overview chapters and then delve into the descriptions of specific current applications to see how they actually work. Important future applications are also outlined, including information storage, materials for computer memories, quantum computers, isotopic fibers, isotopic optoelectronics, and quantum electronics.

The twenty-second Coral Gables conference "UNIFIED SYMMETRY: In the Small and In the Large" continued with the efforts to unify the small and the large. The information gathered with the Huble telescope has in part, in the absence of the SCC , provided a basis for the physicists to unify cosmology and elementary particle physics. The congressional cancellation of the biggest experimental project on the frontiers of physics should not be regarded as an insurmountable obstacle to progress in theoretical physics. The physicists' rise to prominence was mostly reached through their creation of the nuclear era. The post cold war era has somewhat reduced the political, military, and, in part, the social role of the physicist. Some in the administration and the Congress would like physicists to focus on the directly utilitarian aspects of science. Thus, some people do not realize that this regimentation of science would inhibit the creativity. The contributions of solid state physics research to the advancement of technology is the result of physics freely pursued independently of its applications. Modern Physics beginning with Newton's theory of gravity has enabled us to create the space age, to contribute to various technologies, and to impact on our technological modus vivendi.

The 1990 Cargese Summer Institute on ZO-Physics was organized by the Univer- site Pierre et Marie Curie, Paris (M. Levy and J.-L. Basdevant), CERN (M. Jacob), the Universite Catholique de Louvain (D. Speiser and J. Weyers), and the Katholieke Universiteit te Leuven (R. Gastmans), which, since 1975, have joined their efforts and worked in common. It was the ninth Summer Institute on High Energy Physics orga- nized jointly at Cargese by these three universities. Because of the start-up of LEP in the summer of 1989, we broke with our tradition of having our Summer Institutes in the odd years. Indeed, it seemed to us that the many new data from LEP had to be presented in detail as soon as possible in order to prepare the young researchers in particle physics better for the experimental results with which they will be confronted in the coming years. The main theme of the school was therefore ZO-physics, with particular emphasis on the way the experiments at LEP are analyzed. We had one lecturer from each LEP experiment: they agreed among each other to present different topics in e+e- physics. Nevertheless, they made sure that all the major topics were discussed and that the results could be critically compared.

A NATO Advanced Studies Institute was held June 12-23, 1978, at the University of Wisconsin in Madison, Wisconsin. It was a topical Institute in theoretical nuclear physics and had the some what novel feature of focussing not on a single topic but on two closely allied ones: pion-nucleus and heavy-ion physics. These two fields. both dedicated to the investigation of short-wave length properties of nuclei, have many techniques and concepts in cornmon, and essentially become one in the topic of relativistic heavy-ion physics. The purpose of including both in a single Institute was to encourage the practitioners in each of these fields to learn from those in the other; to judge from the liveli ness of the questioning which ensued, the purpose was well-served indeed. Because the Institute was viewed as one which served both educational and research ends, the lecturers took particular pains to develop their subjects in a careful, coherent sequence. The result is a compendium of advanced techniques and current results in these two rapidly-expanding fields of nuclear theory which should serve interested physicists as an ideal introduction to the fields. In addition to the support provided by the Scientific Affairs Division of NATO, substantial financial assistance was provided by the U. S. National Science Foundation and the Graduate School of the University of Wisconsin."

Cosmic electrodynamics is the specific branch of plasma physics which studies electromagnetic phenomena -- mostly the role of electromagnetic forces in dynamics of highly-conducting compressible medium in the solar interior and atmosphere, solar wind, in the Earth's magnetosphere and magnetospheres of other planets as well as pulsars and other astrophysical objects. This textbook is written to be used at several different levels. It is aimed primarily at beginning graduate students who are assumed to have a knowledge of basic physics. Starting from the language of plasma physics, from Maxwell's equations, the author guides the reader into the more specialized concepts of cosmic electrodynamics. The main attention in the book is paid to physics rather than maths. However, the clear mathematical image of physical processes in space plasma is presented and spelled out in the surrounding text. There is not another way to work in modern astrophysics at the quantitative level. The book will also be useful for professional astronomers and for specialists, who investigate cosmic plasmas from space, as well as for everybody who is interested in modern astrophysics.

Over the past five de-:: ades researchers have sought to develop a new framework that would resolve the anomalies attributable to a patchwork formulation of relativistic quantum mechanics. This book chronicles the development of a new paradigm for describing relativistic quantum phenomena. What makes the new paradigm unique is its inclusion of a physically measurable, invariant evolution parameter. The resulting theory has been sufficiently well developed in the refereed literature that it is now possible to present a synthesis of its ideas and techniques. My synthesis is intended to encourage and enhance future research, and is presented in six parts. The environment within which the conventional paradigm exists is described in the Introduction. Part I eases the mainstream reader into the ideas of the new paradigm by providing the reader with a discussion that should look very familiar, but contains subtle nuances. Indeed, I try to provide the mainstream reader with familiar "landmarks" throughout the text. This is possible because the new paradigm contains the conventional paradigm as a subset. The foundation of the new paradigm is presented in Part II, fol owed by numerous applications in the remaining three parts. The reader should notice that the new paradigm handles not only the broad class of problems typically dealt with in conventional relativistic quantum theory, but also contains fertile research areas for both experimentalists and theorists. To avoid developing a theoretical framework without physical validity, numerous comparisons between theory and experiment are provided, and several predictions are made.

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."

For 75 years the stopping of energetic ions in matter has been a subject of great theoretical and experimental interest. The theoretical treatment of the stopping of ions in matter is largely due to the work of Bohr, 1-3 Bethe,4-6 Bloch,7. s and Lindhard,9-12 and it has been reviewed by Bohr,3 Fano,13 17 20 Jackson,14 Sigmund,15 Ahlen,16 and Ziegler et al. - Soon after the discovery of energetic particle emission from radioactive materials, there was interest in how these corpuscles were slowed down in traversing matter. In 1900, Marie Curie stated 21 the hypothesis that Hies rayons alpha sont des projectiles materiels susceptibles de perdre de leur vitesse en travers ant la matiere. " Early attempts to evaluate this were incon- clusive for there was not yet an accurate proposed model of the atom. Enough experimental evidence was collected in the next decade to make stopping power theory one of the central concerns of those attempting to develop an atomic model. J. J. Thomson, director of the prestigious Cavendish Laboratory, and Niels Bohr, a fresh postdoctoral scientist at Rutherford's Manchester Laboratory, both published almost simultaneously22. 23 an analysis of the stopping of charged particles by matter, and each contained many of their divergent ideas on the model of an atom. Thomson ignored in his paper the Rutherford alpha-particle scattering 24 experiment of a year before. But the nuclear atom with a heavy positively 25 charged core was the basis of Bohr's ideas.

This volume focuses on the human exposures and medical effects studies in the SemipaiatinskJ Altai region of Siberia that were a consequence of the radioactive fallout from nuclear test explosions that took place at the Semipalatinsk Test Site of the former Soviet Union. It contains a detailed account of a NATO Advanced Research Workshop (ARW) devoted to the subject, and a selection of the papers presented. The title of the ARW was "Long-term Consequences of Nuclear Tests for the Environment and Population Health (SemipaiatinskJAltai Case Studies)." The estimated exposures to large numbers of people in the Altai lie in an important dose rate and dose domain. Hence the research reported herein provides new and unique information on the effects of radiation on humans. Also emphasized at the ARW were studies involving fallout from the Pacific Island tests of the U. S. A . . There have been over 2300 nuclear weapon test explosions to date. More than 500 took place in the atmosphere and outer space; the remainder were underground. The atmospheric tests comprise the largest source of anthropogenic radioactivity released into the earth's atmosphere to date. The vast majority, in number and yield, were carried out by the former Soviet Union (FSU) and the United States. Each superpower maintained two primary test sites, one continental primarily for small yield tests, and the other more remote for larger yield tests. For the U. S. A.

This book is based on contributions to the NATO Advanced Research Workshop on Recombination of Atomic Ions. This was held at the Slieve Donard Hotel in Newcastle, Northern Ireland, between 6 and 9 October 1991 and attracted 35 participants from 5 countries. The book is inter.~ed to serve as an in-depth review of work to this date on the subject of recombination of atomic ions both in collision with free electrons and with atoms. It contains contributions from almost all groups which have made significant contributions in this area during the last decade. In addition, a synopsis of the discussion session following each of the main subject areas is presented. The material is organized into several themes; an overview of the subject area, theoretical aspects of recombination, experimental measurements of electron-ion recombination and experimental measurement.s of recombination in ion-atom collisions. We would like to acknowledge the sponsorship of the NATO Scientific Affairs Division. We would like to thank the Northern Ireland Tourist Board and the Queen's University of Belfast for providing some additional funding. Finally we would like to thank all the contributors to these proceedings for their efforts in preparing the manuscripts and their assistance in the editing process.

The first presentation of the novel interdisciplinary optical remote sensing technique for various ionized diluted media, based on the collisional polarization of the spectoral emission. The book provides a methodology of the impact spectropolarimetic sensing of many solutions to many practical diagnostic problems.

Reviews of Plasma Physics Volume 22, contains two reviews. The first Cooperative Effects in Plasmas by the late B.B. Kadomtsev is based on the second edition of the author's book in Russian which originated from his written lectures for students of the Moscow Institute of Physics and Technology. Kadomtsev intended to publish the book in English and even initiated the translation himself. The book represents a review of the typical plasma cooperative phenomena that determine the behavior of laboratory and astrophysical plasmas. It is characterized by lively language. The first three sections of the review deal with linear and nonlinear phenomena in fluids without a magnetic field. An additional subsection 'Solitons' has been added to the third section. The next two sections address regular nonlinear phenomena in a plasma in a magnetic field. The second review by S.V. Bulanov et al is connected with the contents of the first. The physics of the laser-plasma interaction including such nonlinear processes as wave breaking, the acceleration of charged particles, electromagnetic wave self-focusing, the relativistic soliton and vortex generation, are considered analytically and illustrated using computer simulations.

The present volume contains the text of the invited talks delivered at the Eighth International Conference on Recent Progress in Many-Body Theories held at SchloB Seggau, Province of Styria, Austria, during the period August 22-26, 1994. The pro ceedings of the Fifth Conference (Oulu, Finland 1987), the Sixth Conference (Arad, Israel 1989) and the Seventh Conference (Minneapolis, USA 1991) have been published. by Plenum as the first three volumes of this series. Papers from the First Conference (Trieste, Italy 1978) comprise Nuclear Physics volume A328, Nos. 1 and 2, the Second Conference (Oaxtepec, Mexico 1979) was published by Springer-Verlag as volume 142 of "Lecture Notes in Physics," entitled "Recent Progress in Many Body Theories." Vol ume 198 of the same series contains the papers from the Third Conference (Altenberg, 1983). These volumes intend to cover a broad spectrum of current research topics in physics that benefit from the application of many-body theories for their elucidation. At the same time there is a focus on the development and refinement of many-body methods. One of the major aims of the conference series has been to foster the exchange of ideas among physicists working in such diverse areas as nuclear physics, quantum chemistry, complex systems, lattice Hamiltonians, quantum fluids and condensed matter physics. The present volume contains contributions from all these areas. th The conference was dedicated on the occasion of Ludwig Boltzmann's 150 birthday."

This volume contains the lectures and contributions presented at the NATO Advanced Study Institute (ASI) on "Frontier Topics in Nuclear Physics", held at Predeal in Romania from 24 August to 4 September 1993. The ASI stands in a row of 23 Predeal Summer Schools organized by the Institute of Atomic Physics (Bucharest) in Predeal or Poiana-Brasov during the last 25 years. The main topics of the ASI were cluster radioactivity, fission and fusion. the production of very heavy elements, nuclear structure described with microscopic and collective models, weak: interaction and double beta decay, nuclear astrophysics, and heavy ion reactions from low to ultrarelativistic energies. The content of this book is ordered according to these topics. The ASI started with a lecture by Professor Greiner on the "Present and future of nuclear physics", showing the most important new directions of research and the interdisciplinary relations of nuclear physics with other fields of physics. This lecture is printed in the first chapter of the book.

Not merely a discussion of small particles or clusters of atoms, molecules, but also the systems they constitute. The goal is to analyse the properties of such finite aggregates and their behaviour in gases and plasmas, and to investigate processes that involve such clusters, based on lectures and seminar problems for graduates. The main part of the book includes more than 200 problems, covering collisions, charge transfer, chemical reactions, condensed systems and their structures, kinetics of cluster growth, excited clusters, the transition from clusters to bulk particles, and small particles, dust, and aerosols in plasmas. Reference data for corresponding parameters of systems under consideration is given in the appendices. Of interest to physicists, astrophysicists, and chemists.

InMay1988,theFirstInternationalConferenceonDissociativeRecombination:Theory, ExperimentandApplicationswasheldatChateauLakeLouise,Alberta,Canada. Thismeeting gaveaconsiderableimpetustothissubject,whichisofparticularinterestforalargevarietyof fieldsincludinginterstellarclouds,planetaryatmospheres,gaslasers,plasmaprocessing,ion sourcesandthermonuclearplasmas. Sincethen,indeed,severalcollaborationswereinitiated betweenexperimentalistsworkingwithdifferenttechniques,betweentheoreticiansdealingwith molecularstructureononehandanddynamicsontheotherhandandalsobetween experimentalistsandtheoreticians. Duringthelastfouryears,therefore,alargenumberof studieswerecarriedoutandraisedanewsetofquestions. Moreparticularly,theresultsthat wereobtainedconcerningcontroversialspeciessuchasH!andHeir,castingsomedoubton theverymechanismsbywhichdissociativerecombinationproceeds. The Second International Conference on Dissociative Recombination: Theory, ExperimentandApplications heldat"I'AbbayedeSaintJacutdelaMer",Brittany,France, May3-8,1992,camethereforeattherighttimetosurveythecurrentstateofthesubject. The symposiumbroughttogetherleadinginvestigatorsinthefieldsofmolecularionrecombination research,atomicandmoleculartheoryandexperiment,plasmasphysics,astrochemistryand aeronomy. Speakerspresentedtalksreviewingtheirownworkandthesewerefollowedby livelydiscussionsessions. Freetimeperiodsallowedparticipantstodiscoveranenchanting peninsulaofNorthBrittanywhilepursuingstimulatingscientificdiscussions. Thepapersinthis volumearebasedonthesetalksandfurtherdiscussions,withtheexceptionofcontributions fromT. AmanoandB. M. McLaughlinwhowereunabletoattend. Alistofparticipantsas wellasasouvenirgroupphotoisgivenattheendofthebook. WeareindebtedtoNATOforitsfinancialsupportwhichcontributedtothegreat successofthissecondmeeting. TheUniversityofRennesIandtheBalzerscompanyarealso acknowledgedfortheiradditionalsupportManythankstothewholestaffoftheabbeyforits kindnessandeffortsinprovidinguswithapropitiousenvironmentforsuchaworkshop. We arealsogratefultoL. Caubetforhervaluableadministrativeassistanceduringthepreparation ofthemeeting. Finallyaspecialmentionmustbegiventoallthesessionchairpersonsfortheir skillinorchestratingthediscussions. Lookingforwardtoattendingthethirdmeeting. TheEditors Bertrand R. Rowe J. Bria/l A. Mitchell Andre Callosa DepartementdePhysique DepartmentofPhysics DepartementdePhysique AtomiqueetMoleculaire TheUniversityofWesternOntario AtomiqueetMoleculaire UniversitedeRennesI London,Canada,N6A3K7 UniversitedeRennesI CampusdeBeaulieu CampusdeBeaulieu 35042RennesCedex, 35042RennesCedex, France France v CONTENTS ORALCONTRIBUTIONS PolyatomicIonDissociativeRecombination . 1 D. R. Bates RecentDevelopmentsandPerspectivesintheTreatmentofDissociative RecombinationandRelatedProcesses...11 A. Giusti-Suzor, I. F Schneider, and 0. Dulieu CharacteristicsofSuperexcitedStatesofMoleculesandMQDTStudiesofNO+ DissociativeRecombination...25 H. Sun, K. Nakashima, and H. Nakamura CalculationsforAr +Xe*andArXe+ +e 35 A. P. Hickman, DL Huestis, and R. P. Saxon Electron-IonContinuum-ContinuumMixinginDissociativeRecombination 47 s. L. Guberman ATheoreticalStudyoftheHCO+andHCS+ElectronicDissociativeRecombinations. . 59 D. Talbi, and Y Ellinger DissociativeRecombinationofCH;:SomeBasicInformationfromElectronic 2 StructureCalculations. 67 WP. Kraemer TheoreticalProblemsintheDissociativeRecombinationofH~ +e...75 H. Takagi RecentMergedBeamsInvestigationsofHydrogenMolecularIonRecombination...87 J B. A. Mitchell, F B. Yousif, P. Van der Donk, and T. J Morgan vii FlowingAfterglowStudiesofElectron-IonRecombinationusingLangmuirProbesand OpticalSpectroscopy...99 NG. Adams RecentFlowingAfterglowMeasurements . 113 B. R. Rowe InfraredSpectroscopicStudiesoftheDissociativeRecombinationProcessesofH...127 3 T. Amano RecombinationofClusterIons . 135 R. Johnsen PredissociationofExcitedStatesofH . . 145 3 H. Helm AStudyofHe e,3I,;)BoundandContinuumStates...155 2 CJ Gillan, B. M McLaughlin. and P. G. Burke ElectronCollisionInducedExcitationsandDissociationofHeH+usingthe R-MatrixMethod . . 163 BK Sarpal, J Tennyson, and L. A. Morgan AssociativeIonisationofHydrogen:ExperimentswithFastMergedBeams...173 F Brouillard, andX Urbain TheoryoftheAsssociativeIonisationReactionbetweenTwoLaser-Excited . 187 SodiumAtoms 0. Du!ieu, A. Giusti-Suzor, andF Masnou-Seeuws ResonantTheoryofDissociativeAttachment...195 J. J. Fabrikant MicroscopicandMacroscopicTheoriesofTermolecularRecombinationbetween AtomicIons...205 MR. Flannery DissociativeRecombinationinPlanetaryIonospheres . . 219 JL. Fox ChemistryofSupernova1987a . 243 A. Dalgarno DissociativeRecombinationinInterstellarClouds . .

At extremely low temperatures, clouds of bosonic atoms form what is known as a Bose-Einstein condensate. Recently, it has become clear that many different types of condensates -- so called fragmented condensates -- exist. In order to tell whether fragmentation occurs or not, it is necessary to solve the full many-body Schrodinger equation, a task that remained elusive for experimentally relevant conditions for many years. In this thesis the first numerically exact solutions of the time-dependent many-body Schrodinger equation for a bosonic Josephson junction are provided and compared to the approximate Gross-Pitaevskii and Bose-Hubbard theories. It is thereby shown that the dynamics of Bose-Einstein condensates is far more intricate than one would anticipate based on these approximations. A special conceptual innovation in this thesis are optimal lattice models. It is shown how all quantum lattice models of condensed matter physics that are based on Wannier functions, e.g. the Bose/Fermi Hubbard model, can be optimized variationally. This leads to exciting new physics."

The reviews in this volume address advances in three important but diverse areas of nuc1ear physics. Within nuc1ear physics it would be hard to provide a wider range of subject matter, style, or treatment. The first artic1e, on quark bags, is a pedagogic artic1e intended to make accessible to the nuc1ear physics community important new ideas from partic1e physics. The second, on interacting boson models, reviews a very interesting and controversial new approach to some of the central problems of nuc1ear spectroscopy. The third, on relativistic heavy-ion physics, is a guide to the extensive literature on a new subject which has been fuH of great expectations, puz zling data, and speculative ideas. In the past decade, partic1e theorists' understanding of the structure of hadrons has undergone a revolution strikingly similar to that brought about in nuc1ear physics by the introduction of the Iluc1ear sheH model. Like the sheH model, the bag model of hadrons phenomenologically specifies an interior region in which constituents are confined and described by single-partic1e wave functions that are only weakly perturbed by residual interactions."

This book presents the latest advances in ultrafast science, including ultrafast laser and measurement technology, and studies of ultrafast phenomena. It summarizes the results presented at the 12th Ultrafast Phenomena Conference and reviews the state of the art of this important and rapidly advancing field.

The Editors have pleasure in presenting a further volume in the se ries to our international audience. Perhaps the most significant event of the passing year has been the publication by the IAEA of its study of the prob lem of continuing radiation protection in the lands surrounding Chernobyl. The major international project undertaken in 1990 and reported in 1991 is worth reading, not only for its assessment of how radiation protection intervention should be applied de facto in accident conditions, but equally for its account of the modern view of the philosophy of radiation protection. Some would, however, wish to argue that the acknowledgement by Iraq of its three-pronged development of nuclear weapons in conditions of secrecy and antagonism was equally significant and indeed as much a deter minant of the future of peaceful nuclear power as the Chernobyl accident. But it must be clear that the developments of weapons and electricity pro duction are not inescapably bound together; the Iraqi weapons program was not linked to any peaceful power development.

Numerous experiments and calculations have shown that isolated metal clusters possess many interesting features, quite different from those known from surface and solid- state physics or from atomic and molecular physics. The technological exploitation of these new properties, e.g. in miniature electronic or mechanical components, requires the cluster to be brought into an environment such as an encapsulating matrix or a surface. Due to the interaction with the contact medium, the properties of the clusters may change or even disappear. Thus the physics of cluster-on-surface systems -- the main subject of this book -- is of fundamental importance. The book addresses a wide audience, from the newcomer to the expert. Starting from fundamental concepts of adsorbate-surface interactions, the modification of electronic properties through electron confinement, and concepts of cluster production, it elucidates the distinct properties of the new metallic nanostructures.

Since the early days of modem physics spectroscopic techniques have been employed as a powerful tool to assess existing theoretical models and to uncover novel phenomena that promote the development of new concepts. Conventionally, the system to be probed is prepared in a well-defined state. Upon a controlled perturbation one measures then the spectrum of a single particle (electron, photon, etc.) emitted from the probe. The analysis of this single particle spectrum yields a wealth of important information on the properties of the system, such as optical and magnetic behaviour. Therefore, such analysis is nowadays a standard tool to investigate and characterize a variety of materials. However, it was clear at a very early stage that real physical compounds consist of many coupled particles that may be excited simultaneously in response to an external perturbation. Yet, the simultaneous (coincident) detection of two or more excited species proved to be a serious technical obstacle, in particular for extended electronic systems such as surfaces. In recent years, however, coincidence techniques have progressed so far as to image the multi-particle excitation spectrum in an impressive detail. Correspondingly, many-body theoretical concepts have been put forward to interpret the experimental findings and to direct future experimental research. This book gives a snapshot of the present status of multi-particle coincidence studies both from a theoretical and an experimental point of view. It also includes selected topical review articles that highlight the achievements and the power of coincident techniques.

The theoretical chemist is accustomed to judging the success of a theoretical prediction according to how well it agrees with an experimental measurement. Since the object of theory is the prediction of the results of experiment, that would appear to be an entirely satisfactory state ofaffairs. However, ifit is true that "the underlying physicallaws ...for the whole ofchemistryare ...completely known" (1), thenit shouldbepossible,atleastinprinciple, topredict theresults of experiment moreaccurately than they canbe measured. Ifthe theoreticalchemist could obtain exact solutions ofthe Schrodinger equation for many-body systems, then the experimental chemist would soon become accustomed to judging the success ofan experimental measurement by how well it agrees with a theoretical prediction. In fact, it is now possible to obtainexact solutions ofthe Schrodinger equation for systems ofa few electrons(2-8). These systems include the molecular ion Ht, the molecule H , the reaction intermediate H-H-H, the unstable pair H-He, the 2 stable dimer He2' and the trimer He3. The quantum Monte Carlo method used in solving the time-independent Schrodinger equation for these systems is exact in that it requires no physical or mathematical assumptions beyond those of the Schrodinger equation. As in most Monte Carlo methods there is a statistical or sampling error which is readily estimated.