Atoms, Molecules and Photons: An Introduction to Atomic-, Molecular- and Quantum Physics

608 Pages·2010·8.75 MB·English

by  Wolfgang Demtröder (auth.)

Demtröder
Atoms, Molecules and Photons
GRADUATE TEXTS IN PHYSICS
Graduate Texts in Physics publishes core learning/teaching material for graduate- and
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entering,orrequiringtimelyknowledgeof,aresearchfield.
SeriesEditors
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Wolfgang Demtröder
Atoms, Molecules
and Photons
An Introduction to Atomic-, Molecular-
and Quantum-Physics
With677Figuresand42Tables
123
ProfessorDr.WolfgangDemtröder
UniversitätKaiserslautern
FBPhysik
Erwin-Schrödinger-Str.46
67663Kaiserslautern
Germany
[email protected]
ISSN1868-4513 e-ISSN1868-4521
ISBN978-3-642-10297-4 e-ISBN978-3-642-10298-1
DOI10.1007/978-3-642-10298-1
SpringerHeidelbergDordrechtLondonNewYork
LibraryofCongressControlNumber:2010935944
(cid:4)c Springer-VerlagBerlinHeidelberg2006,2010
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Preface to the Second Edition
The first edition of this textbook had found a friendly acceptance. This second
edition does not change the concept of the representation which combines the ex-
perimentaltechniquesfortheinvestigationofatomsandmoleculesandtheirresults
that have lead to the development of quantum physics. Some new developments
in laser physics and quantum optics have been inserted in Chapter 12 in order to
givethereadersomeideasaboutthefrontiersinthesefieldsregardingexperimental
techniquesandphysicalinsight.
This second edition represents a thoroughly revised version of the first edition,
which,unfortunately,containedalotoferrorsandmisprints.Iamgratefultomany
readers who have informed me about such errors and who offered corrections and
improvementsoftherepresentationforabetterunderstanding.Iamparticularlyin-
debtedtoDr.NicoDam,RaboudUniversityNijmegen,NetherlandandProf.Zamik
Rosenwaks,BenGurionUniversity,Israel,whohavesentmeanextensivecorrection
list.
The author hopes, that this new edition will be well accepted and that critical
readerswillsendtheircommentsorideasaboutpossibleimprovements.
I thank Dr. Th. Schneider, Springer Verlag for his continuous interest and
encouragement.
Kaiserslautern,
October2010 WolfgangDemtröder

Preface to the First Edition
Thedetailedunderstandingofmatter,itsphasetransitionsanditsinteractionwithra-
diationcouldbeonlyreached,afteritsmicroscopicstructuredeterminedbythekind
of atoms or molecules as basic constituents of matter had been investigated. This
knowledge allowed the controlled optimization of characteristic properties of mat-
ter.Atomicphysicsthereforerepresentsnotonlyanareaofimportantfundamental
research,buthasfurthermoremanyapplicationswhichhaveessentiallyformedour
present technical world. The understanding of materials and their use in daily life,
hasmajorimpactofourcultureandourattitudetowardsnatureandourenvironment.
This textbook is aimed as an introduction to the microscopic world of atoms,
moleculesandphotons.Itillustrateshowourknowledgeaboutthemicroscopicstruc-
ture of matter and radiation came about and which crucial experiments forced an
extension andrefinement ofexistingclassical theories,culminating inthedevelop-
ment of quantum theory, which is now accepted as the basic theory of atomic and
molecularphysics.
The book therefore starts with a short historical review about the role of ex-
periments for correcting erroneous ideas and proving the existence of atoms and
molecules.Thecloseinteractionbetweenexperimentsandtheoryhasbeenoneofthe
reasonsfortherapiddevelopment ofatomicphysicsinthe19th and20th centuries.
Examplesarethekinetictheoryofgases,whichcouldbecompletelyunderstoodby
theassumptionofmovingatomsinthegas,orthepostulationofenergyquantainthe
radiation field, which could explain the discrepancy between measurements of the
spectralenergydistributionofthermalradiationfieldsandclassicalelectrodynamics.
The new ideas of quantum physics and their corroboration by experiments are
discussed in Chap. 3 while the fundamental equations of quantum mechanics and
theirapplicationstosomesimpleexamplesareexplainedinChap.4.
Atheorycanbebestunderstoodbyapplicationstoarealsituation.InChap.5the
quantumtheoryofthesimplestrealsystem,namelythehydrogenatom,ispresented.
Hereitisagainillustrated,thatexperimentsenforcedanextensionofquantumme-
chanicstoquantumelectrodynamicsinordertounderstandallexperimentalresults.
ThedescriptionoflargeratomswithmanyelectronsistreatedinChap.6,whichalso
reducesthechemicalpropertiesofchemicalelementstothestructureoftheelectron
shellsandexplainswhyallelementscanbearrangedinaperiodictable.
The important subject of interaction of matter with radiation is discussed in
Chap.7.Thispreparesthegroundfortheexplanationoflasers,treatedinChap.8.
Molecules,consistingoftwoormoreatoms,formthebasisforthegreatvariety
ofourworld.TheyarediscussedinChaps.9and10.Inparticularthequestion,why
and how atoms can form stable molecules, and which kind of interaction occurs,
VIII PrefacetotheFirstEdition
is treated in more detail. In Chap. 11 the different experimental techniques for the
investigationofatomsandmoleculesarepresented,inordertogivethereaderafeel-
ingfortheinventiveideasandthenecessaryexperimentalskillfortheirrealization.
The last chapter presents a short overview on recent developments in atomic and
molecular physics, which shall demonstrate that physics will be never a complete
andfinalizedfield.Thereisstillmuchtoexploreandnewideasandscientificenthu-
siasmisneeded,topushtheborderofourknowledgefurtherahead.Someexamples
in this chapter also illustrate possible important applications of new ideas such as
thequantumcomputerornewtechniquesoffrequencymetrologyusedintheworld
wideglobalpositioningsystemGPS.
Manypeoplehavehelpedtopublishthisbook.FirstofallIwouldliketothank
theteamofLE-TeX,whohavemadethelayout.InparticularUweMatrisch,whohas
lookedaftertheeditingprocessandwhohastakencareofmanyhandwrittenremarks
andcorrectionsoftheauthorwithgreatpatience.Dr.SchneiderfromSpringer-Verlag
hasalwayssupportedthisproject,althoughittooklongerasanticipated.
Manythanksgotoallcolleagueswhohavegiventheirpermissiontoreproduce
figuresortables.
Thisbookisanextended versionofvolume 3ofaGerman textbook consisting
of4volumes.Theauthorshopes,thatitwillfindacomparablegoodacceptanceas
theGermanversion.Hewillbegratefulforanyreplyofreaders,givingcorrections
of possible errors or hints to improvements. Any of such replies will be answered
assoonaspossible.Atextbooklivesfromtheactivecollaborationofitsreadersand
theauthorlooksforewardtoalivelycorrespondencewithhisreaders.Hehopesthat
thisbookcancontributetoabetterunderstandingofthisfascinatingfieldofatoms,
moleculesandphotons.
Kaiserslautern,
August2005 WolfgangDemtröder
Contents
1. Introduction
1.1 ContentsandImportanceofAtomicPhysics . . . . . . . . . . . 1
1.2 Molecules:BuildingBlocksofNature . . . . . . . . . . . . . . . 3
1.3 SurveyontheConceptofthisTextbook . . . . . . . . . . . . . . 4
2. TheConceptoftheAtom
2.1 HistoricalDevelopment . . . . . . . . . . . . . . . . . . . . . . 7
2.2 ExperimentalandTheoreticalProofsfortheExistence
ofAtoms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.2.1 Dalton’sLawofConstantProportions . . . . . . . . . 9
2.2.2 TheLawofGay-LussacandtheDefinition
oftheMole . . . . . . . . . . . . . . . . . . . . . . . 11
2.2.3 ExperimentalMethodsfortheDetermination
ofAvogadro’sConstant . . . . . . . . . . . . . . . . . 12
2.2.4 The Importance of Kinetic Gas Theory
fortheConceptofAtoms . . . . . . . . . . . . . . . . 17
2.3 CanOneSeeAtoms? . . . . . . . . . . . . . . . . . . . . . . . 20
2.3.1 BrownianMotion . . . . . . . . . . . . . . . . . . . . 20
2.3.2 CloudChamber . . . . . . . . . . . . . . . . . . . . . 24
2.3.3 MicroscopeswithAtomicResolution . . . . . . . . . . 24
2.4 TheSizeofAtoms . . . . . . . . . . . . . . . . . . . . . . . . . 29
2.4.1 The Size of Atoms in the Van der Waals
Equation . . . . . . . . . . . . . . . . . . . . . . . . . 29
2.4.2 Atomic Size Estimation from Transport
Coefficients . . . . . . . . . . . . . . . . . . . . . . . 29
2.4.3 AtomicVolumesfromX-RayDiffraction . . . . . . . . 31
2.4.4 ComparisonoftheDifferentMethods . . . . . . . . . . 32
2.5 TheElectricStructureofAtoms . . . . . . . . . . . . . . . . . . 33
2.5.1 CathodeRaysandKanalstrahlen . . . . . . . . . . . . 34
2.5.2 MeasurementoftheElementaryChargee . . . . . . . 35
2.5.3 HowtoProduceFreeElectrons . . . . . . . . . . . . . 37
2.5.4 GenerationofFreeIons . . . . . . . . . . . . . . . . . 39
2.5.5 TheMassoftheElectron . . . . . . . . . . . . . . . . 41
2.5.6 HowNeutralistheAtom? . . . . . . . . . . . . . . . . 44
2.6 ElectronandIonOptics . . . . . . . . . . . . . . . . . . . . . . 45
2.6.1 RefractionofElectronBeams . . . . . . . . . . . . . . 45
2.6.2 ElectronOpticsinAxiallySymmetricFields . . . . . . 47