Table Of ContentSpringerSerieson
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
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–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.
