SpringerSerieson ATOMIC, OPTICAL, AND PLASMA PHYSICS 46 SpringerSeries on ATOMIC, OPTICAL, AND PLASMA PHYSICS TheSpringerSeriesonAtomic,Optical,andPlasmaPhysicscoversinacompre- hensivemannertheoryandexperimentintheentirefieldofatomsandmolecules and their interaction with electromagnetic radiation. Books in the series provide a rich source of new ideas and techniques with wide applications in fields such aschemistry,materialsscience,astrophysics,surfacescience,plasmatechnology, advanced optics, aeronomy, and engineering. Laser physics is a particular con- nectingthemethathasprovidedmuchofthecontinuingimpetusfornewdevelop- mentsinthefield.Thepurposeoftheseriesistocoverthegapbetweenstandard undergraduatetextbooksand the research literaturewith emphasis on the funda- mentalideas,methods,techniques,andresultsinthefield. 47 SemiclassicalDynamicsandRelaxation ByD.S.F.Crothers 48 TheoreticalFemtosecondPhysics AtomsandMoleculesinStrongLaserFields ByF.Großmann 49 RelativisticCollisionsofStructuredAtomicParticles ByA.VoitkivandJ.Ullrich 50 CathodicArcs FromFractalSpotstoEnergeticCondensation ByA.Anders 51 ReferenceDataonAtomicPhysicsandAtomicProcesses ByB.M.Smirnov Vols.20–46oftheformerSpringerSeriesonAtomsandPlasmasarelistedattheendofthebook Bernd Lohmann Angle and Spin Resolved Auger Emission Theory and Applications to Atoms and Molecules With45 Figures Dr.BerndLohmann UniversitätMünster,InstitutfürTheoretischePhysik Wilhelm-Klemm-Str.9,48149Münster,Germany E-mail:[email protected] TheWombat,poembyClaudiaLehmann,©ClaudiaLehmann,1994 SpringerSeriesonAtomic,Optical,andPlasmaPhysics ISSN1615-5653 ISBN978-3-540-74629-4 e-ISBN978-3-540-74630-0 LibraryofCongressControlNumber:2008929557 ©Springer-VerlagBerlinHeidelberg2009 Thisworkissubjecttocopyright.Allrightsarereserved,whetherthewholeorpartofthematerialis concerned,specificallytherightsoftranslation,reprinting,reuseofillustrations,recitation,broadcasting, reproductiononmicrofilmorinanyotherway,andstorageindatabanks.Duplicationofthispublication orpartsthereofispermittedonlyundertheprovisionsoftheGermanCopyrightLawofSeptember9, 1965,initscurrentversion,andpermissionforusemustalwaysbeobtainedfromSpringer-Verlag.Vio- lationsareliabletoprosecutionundertheGermanCopyrightLaw. Theuseofgeneraldescriptivenames,registerednames,trademarks,etc.inthispublicationdoesnot imply,evenintheabsenceofaspecificstatement,thatsuchnamesareexemptfromtherelevantprotective lawsandregulationsandthereforefreeforgeneraluse. Typesettingandproduction:VTEX Coverconcept:eStudioCalmarSteinen Coverdesign:WMXDesignGmbH,Heidelberg SPIN11673309 57/3180/VTEX Printedonacid-freepaper 987654321 springer.com –TomywifeandtoTanya,ourlittleMausebär. – –AndtoalltheWombatsofAustralia.– TheWombat Cutestlittlething onEarth Imethere– whichreallymakes itworth tocarefor !! ClaudiaLehmann, Melbourne,1994 Foreword It is widely recognised by the international scientific community that in the early decadesofthetwentiethcenturyremarkableadvancesweremadeinlayingthefoun- dationsforunderstandingthefundamentalpropertiesofatomsandmolecules.There wasarichinteractionbetweenexperimentalandtheoreticaldevelopmentsleadingto somefundamentaldiscoveries.Scientiststhataresynonymouswiththaterainclude Einstein, Bohr, Planck, Schrödinger and Dirac. The photoionization of an atom, molecule or solid ejecting an electron was explained on the basis of the Einstein Photoelectric Effect, discovered in 1905, and the subsequent de-excitation of the speciesfollowinginnershellionisationbyaradiativeX-rayemissionprocess.Itwas not until the pioneering work of Pierre Auger in the 1920s that the importance of analternativecompetitivepathwaytoX-rayradiativede-excitationwasrecognised. Thisalternativepathway,nowknownastheAugerEffect,involvestheejectionofa second electron via a non-radiative emission process resulting in the de-excitation ofthespecies. Many decades later following the refinement of quantum theory and the avail- abilityofpowerfulcomputersandtuneablesynchrotronlightsources,therichness to the electronic structure information imbedded in the correlated emission of the photoelectron and the Auger electron from an atom or molecule was able to be recognisedandunderstood.TheearliestAugerelectronspectralstudieswerelargely confinedtotheinvestigationofAugerenergiesanddecayrates;however,sincethe 1980smanyontheinvestigationshavefocusedonangularandspinresolvedeffects. In this book Bernd Lohmann provides a detailed account of theoretical develop- mentsinthestudyofangularandspinresolvedAugerprocesses,principallyassoci- atedwithfreeatoms,withonechapterdevotedtodiatomicmolecules.Mostofthis work hasbeenreported inthe internationalliteratureoverthepast 30years and is directlylinkedtotheunderstandingofexperimentaldata. Theprincipalemphasisofthepresentwork,therefore,isthegatheringtogether forthecurrentstatusofourknowledgeoftheAugereffectthrougharigorouspre- sentation of theoretical approaches coupled with numerical methods to calculate Augerenergies,decayrates,angulardistributionsandspinpolarisationproperties. Thisworkwillbeinvaluabletoexperiencedtheoreticiansandexperimentalistsseek- ingtogainadeeperunderstandingofsomepropertiesofatomsandmoleculesasso- ciatedwithmultipleelectronemission. viii Foreword Theraregasatomsaretheprincipalreferencepointsformanyofthetheoretical andexperimentalstudiesreported.Theyareusedinthisworktoillustratethetheo- reticalmethodsprincipallydevelopedorrefinedbyLohmannandhiscollaborators. Whatonehaslearnedistheimportanceofaccountingforrelativisticandcorrelation effectswhenaccuratelymodelingthebehaviourofelectronsinatomicsystems.Ex- tensionstoopenshellsystems,whilegenerallymorecomplex,canbetreatedwithin the same framework. The elucidation of molecular Auger spectra is considerably morecomplex.Aninsightintothisfieldisprovidedmainlythroughanaccountof Augerprocessesindiatomicmolecules. Manyadvanceshavebeenmadeinunderstandingthefundamentalinformation contained in the two electron emission process since the original experiments of PierreAugerin1923.BerndLohmannhasproducedacomprehensive,wellwritten text that will be viewed as a significant contribution to the field of Auger electron spectroscopy.Thisbookwillbeamostusefulreferenceforthoseresearcherswish- ingtofurtheradvancethefield. Melbourne,May2008 FrankP.Larkins Preface TheAugeremissionhasbeendetectedbyPierreAugermorethaneightyyearsago; shortafter thebeginningof quantummechanics.Theobservationof radiationfree transitionsperfectlycomplementedthecaseofelectronemissionduetophotonim- pact.Theemissionofanelectronafterphotoionizationhadbeenalreadyunderstood andexplainedbytheworkofEinstein(1905,Nobelprize1921forthephotoelectric effect).Wentzel(1927)wasfirstbytheoreticallyinterpretingtheAugeremissionas a process caused by a two-particle interaction. Since photoionization had been al- ready explained as a single-particle interaction effect, and due to the fact that first experimentsmainlyconcentratedonthedetectionofthevalenceshellelectrons,the investigation of radiation free transitions, i.e. the Auger effect, showed only little developmentduringtheearlydecadesofthelastcentury.Onlystartingintheearly 1980s,scientificinterestcameback.Thishasbeencausedduetotheavailabilityof improvedandmoredevelopeddetectionmethodsand,onthetheoreticalside,bythe applicationofadvancedmethodsofdensitymatrixtheorywhichallowedformore precisepredictions,likeangulardistributionandspinpolarization,oftheobserved particles, i.e. the Auger electrons. It is worth pointing out that both, theoretical as well as experimental progress, benefited from efforts which had been made in the fieldofnuclearphysics.InparticulartheworkbyFano(1957)andco-workersneed to be mentioned who first adapted the nuclear physics methods and successfully appliedthemtoelectronemissionproblemsinatomicphysics.Adoptingtheexper- imental techniques of nuclear physics, like angle and spin resolved observation of particles,therehasalwaysbeen,andstillis,needforatheoreticalinterpretationand prediction of angle and spin resolved data. This need is even more urgent due to the fact that, after starting investigations of angle and spin resolved Auger emis- sionintheearly1980s,thescientificcommunityistoday,duetotheavailabilityof thirdgenerationsynchrotronradiationsourcesandmorerefineddetectionmethods, abletoproduceandobtainreliabledatawhichcanbecomparedwiththetheoretical predictions.This bookis intendedto focus on these still importantareas of Auger emission theory. Our aim is to derive the theoretical framework and to provide a numberofdataandusefulrelationsnecessaryfortheinterpretationofpresentand forthcomingexperiments. Themainaimofthisbookistwofold.Ontheonehand,thisbookmightbeseen as a theoretical introduction into the broad field of angle and spin resolved elec- tronemissionprocesses,givingacomprehensivesurveyofnowadaysAugeremis- x Preface sionphysicsfortheadvancedpre-andpost-graduatestudent.Strictlyapplyingthe methodsofdensitymatrixyieldsageneralbasisfortheinterpretationandanalysis andleadstomoreadvancedapplications. On the other hand, this book provides a comprehensive compendium for the active researcher on performed, current, and outlined foreseen research, related to the Auger decay, which might be useful for the planning and performing of even more exciting and sophisticated studies in a field of physics which concerns areas of not only atomic and molecular physics, but also emerging fields like chemo- or biophysical applications, or even quantum information. In addition, the kind of obtained data is important for the knowledge and interpretation of different types of radiation spectra observed from NASA, ESA and the Hubble Space Telescope which will provide a database on cross sections for electron impact excitation, of highlychargedions,electron-ionrecombination,photoionization,chargetransfers, andX-rayemission. AnintroductionintothefieldofangleandspinresolvedAugeremissionwillbe giveninthefirstchapterofthebookandtheparticularfocusofthesubsequentchap- terswillbediscussed.ThegeneraltheoryofangleandspinresolvedAugeremission andtherelevantequationswillbederivedinChap.2.Numericalmethodsandrelated programpackageswillbeintroducedinChap.3.Chapter4coversthebroadfieldof examplesandapplicationsandthecomparisonofexperimentalandnumericaldata andtheirinterpretation.Eventually,Chap.5dealswiththefieldofmolecularAuger processes,whilethelastchaptergivesanoutlookofcurrent,plannedandforeseen researchrelatedtoAugeremission.Anumberofusefulequationsandrelationswill begivenorderivedinthesubsequentAppendix. Fortunately, research is still ongoing and never ends, thus, I am delighted to receivetheoutcomesofnewresearchers. AtthispointIwouldliketosaythankstothenumerousandhelpfulpeopleover alltheseyearswhocontributedwiththeirefforts,expertise,andvaluablediscussions inrealizingthisbook.Themanydiscussionswithmyco-workersandcollaborators oftenstimulatedthebeginningofanewresearchprojector,ontheotherhand,led investigationsintotherightdirection. First of all I would like to express my sincere thanks to Prof. Dr. K. Blum of the University of Münster. I have been a member of his group since many years and we often had inspiring discussions which have been most helpful in the for- mulationandclarificationofthegeneraltheory.Besides,healwaystriedtosupport me financially. I am also thankful to the former members of his group, Prof. Dr. K. Bartschat, and Drs. S. and K. Bonhoff, A. Busalla, A. Dellen, R. Fandreyer, U.Kleiman,J.Lehmann,M.Musigmann,R.P.Nordbeck,A.Raeker,E.Taute,and G.Wösteformanyhelpfuldiscussionsandtheniceatmosphere. During my years in Münster, there has been always a close collaboration with the experimental groups and I am thankful to Prof. Dr. J. Kessler and Prof. Dr. G.F.Hannefortheirongoinginterestinmyresearch.Inparticular,Iwouldliketo thank Prof. Dr. H. Merz. In his group the first experiments on spin polarized Au- Preface xi ger emission have been performed, and our common discussions have been often stimulatingforthefurtherdevelopmentofboth,experimentandtheory. IamalsothankfultoProf.Dr.W.MehlhornoftheUniversityofFreiburgforhis ongoinginterestinmywork,and,forinvitingmetoFreiburgwhereIfirstmetProf. Dr.N.M.KabachnikofMoscowStateUniversitywithwhomIstartedafruitfuland longcollaborationinthefieldofAugeremission.Thiscollaborationhasbeenlater extended by including Prof. Dr. A. Grum-Grzhmailo of Moscow State University andstillyieldsafruitfuloutput. I am particularly indebted to Prof. Dr. U. Becker and also to Priv.-Doz. Dr. U. Hergenhahn of the Fritz-Haber Institut (FHI) of the Max-Planck-Gesellschaft (MPG)withwhomIhaveafruitfulandstillongoingcollaboration.Duringmyvar- ious stays at the FHI in Berlin the theory of resonant Auger transitions has been furtherdeveloped.IamverygratefultoProf.Dr.U.Beckerformanyinspiringdis- cussionsandformanytimesprovidingfinancialsupportwhicheventuallyenabled forthepreparationofthisbook.Iamalsothankfultohiscurrentandformergroup membersDrs.B.Langer,J.ViefhausandM.Braunefordiscussionsandhelpwith partofthefiguresandforprovidingmostofthenecessarysoftwarewhichhascome intoeffectduringthepreparationofthemanuscript. I am most thankful to Prof. Dr. F.P. Larkins who invited me to Australia and Dr. T.E. Meehan with whom I worked in School of Chemistry during my stay at the University of Melbourne, Australia. Working interdisciplinary, as a physicist in theoretical chemistry, has been proofed to be most fruitful for both sides. First ideasinthefieldofmolecularAugeremissionhavebeeninventedduringmytime in Melbourne, and parts of the results presented in this book have been obtained. I very much appreciate the hospitality which has been extended to me during my stay,andalsotheniceintroductiontotheAustralianlife-style. ThereisanongoingcollaborationwithApl.Prof.Dr.S.FritzscheoftheUniver- sityofKasselwithwhomIstartedtheworkonopenshellatomsandIamthankful fortheongoingandinspiringdiscussions. Further,IwouldliketothankProf.Dr.A.K.EdwardsoftheUniversityofGeor- giaforstimulatingdiscussionsinthefieldofmolecularAugeremission. I am also thankful to Drs. B. Nestmann and B. Schimmelpfennig of the Uni- versityofBonnforvaluablediscussionsandsupportwiththenumericalresultsob- tainedformolecularAugerprocesses. Eventually,IamindebtedtoProf.Dr.H.KleinpoppenoftheUniversityofStir- ling for his support and for inviting me to Stirling. Besides our common research interestshehasbeenalwaysinterestedinmyworkandwehadlongandmosthelp- fuldiscussions.Ioftenappreciatedhistalentofbringingallthingsbacktonormal irrespectiveofphysicsornon-physicsproblems. I am most thankful to Prof. Dr. K. Blum and to Dr. U. Kleiman for carefully proof-readingthemanuscriptandforgivingvaluablesuggestionsandremarks.Iam dearlythankfultomywife,Dipl.Bio.C.Lehmann,forthetaskofdouble-checking theindex.