Atoms in Intense Laser Fields

582 Pages·2011·6.517 MB·English

by  Joachain C.J., Kylstra N.J., Potvliege R.M.

ATOMS IN INTENSE LASER FIELDS
Thedevelopmentoflaserscapableofproducinghigh-intensitypulseshasopened
anewareainthestudyoflight–matterinteractions.Thecorrespondinglaserfields
arestrongenoughtocompetewiththeCoulombforcesincontrollingthedynamics
of atomic systems, and give rise to multiphoton processes. This book presents a
unifiedaccountofthisrapidlydevelopingfieldofphysics.
Thefirstpartdescribesthefundamentalphenomenaoccurringinintenselaser–
atom interactions and gives the basic theoretical framework to analyze them.
The second part contains a detailed discussion of Floquet theory, the numerical
integration of the wave equations and approximation methods for the low- and
high-frequencyregimes.Inthethirdpart,themainmultiphotonprocessesaredis-
cussed: multiphoton ionization, high harmonic and attosecond pulse generation
andlaser-assistedelectron–atomcollisions.Aimedatgraduatestudentsinatomic,
molecular and optical physics, the book will also interest researchers working on
laserinteractionswithmatter.
c. j. joachainisEmeritusProfessorofTheoreticalPhysicsattheUniversityof
Brussels.Hisresearchactivitiesconcernquantumcollisiontheoryandtheinterac-
tionofintenselaserfieldswithmatter.Hehasreceivedmanyscientificawardsand
distinctions,inparticulartheAlexandervonHumboldtPrize.
n. j. kylstra is currently employed in the financial services industry, and is a
researchfellowattheUniversityofBrussels.Hisresearchincludestheinteraction
ofatomswithhigh-intensitylaserfields.
r. m. potvliegeiscurrentlyReaderinPhysicsattheUniversityofDurham.His
researchinterestscoverthetheoreticalaspectsofmultiphotonprocessesinintense
laserfields.

ATOMS IN INTENSE
LASER FIELDS
C. J. JOACHAIN
UniversityofBrussels
N. J. KYLSTRA
UniversityofBrussels
R. M. POTVLIEGE
UniversityofDurham
cambridge university press
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©C.Joachain,N.KylstraandR.Potvliege2012
Thispublicationisincopyright.Subjecttostatutoryexception
andtotheprovisionsofrelevantcollectivelicensingagreements,
noreproductionofanypartmaytakeplacewithoutthewritten
permissionofCambridgeUniversityPress.
Firstpublished2012
PrintedintheUnitedKingdomattheUniversityPress,Cambridge
AcataloguerecordforthispublicationisavailablefromtheBritishLibrary
LibraryofCongresscataloguinginPublicationdata
Joachain,C.J.(CharlesJean)
Atomsinintenselaserfields/C.J.Joachain,N.J.Kylstra,andR.M.Potvliege.
p. cm.
Includesbibliographicalreferencesandindex.
ISBN978-0-521-79301-8(hardback)
1. Electron-atomcollisions. 2. Floquettheory. 3. Laserpulses,Ultrashort. 4. Multiphotonprocesses.
5. Multiphotonionization. I. Kylstra,N.J. II. Potvliege,R.M. III. Title.
QC793.5.E628J632011
(cid:1)
539.72–dc23 2011024273
ISBN978-0-521-79301-8Hardback
CambridgeUniversityPresshasnoresponsibilityforthepersistenceor
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Felixquipotuitrerumcognoscerecausas.
(Virgil,Georgics,II,490)

Contents
Preface page xi
PartI Basicconcepts 1
1 High-intensitylaser–atomphysics 3
1.1 Introduction 3
1.2 High-intensitylasers 5
1.3 Multiphotonionizationandabove-thresholdionization 10
1.4 Harmonicgenerationandattosecondpulses 21
1.5 Laser-assistedelectron–atomcollisions 29
2 Theoryoflaser–atominteractions 37
2.1 Classicaldescriptionofalaserfield 37
2.2 Classicalnon-relativisticelectrondynamicsinalaserfield 52
2.3 Time-dependentSchrödingerequation 57
2.4 Gaugetransformations 62
2.5 TheKramerstransformation 65
2.6 Theevolutionoperator 66
2.7 Gordon–Volkovwavefunctions 68
2.8 Non-dipoleeffects 71
2.9 Relativisticeffects 75
PartII Theoreticalmethods 91
3 Perturbationtheory 93
3.1 Time-dependentperturbationtheoryfortheevolution
operator 93
3.2 Methodofvariationoftheconstants 125
3.3 Semi-perturbativemethods 137
vii
viii Contents
4 Floquettheory 141
4.1 HermitianFloquettheory 142
4.2 Bound–boundFloquetdynamics 155
4.3 Floquetdressedcontinuumstates 170
4.4 Non-HermitianFloquettheory 179
4.5 FloquettheoryintheKramers–Hennebergerframe 191
4.6 Sturmian-Floquettheory 194
4.7 R-matrix–Floquettheory 196
5 Numericalintegrationofthewaveequations 218
5.1 Discrete-timepropagators,representationsofthewave
functionandchoiceofgauge 219
5.2 Calculationoftheobservables 232
5.3 One-andtwo-dimensionalstudiesofthetime-dependent
Schrödingerequation 236
5.4 Time-dependentSchrödingerequationforatomic
hydrogen 241
5.5 Time-dependentSchrödingerequationforcomplexatoms 247
5.6 Non-dipoleeffects 258
5.7 Relativisticeffects 260
6 Thelow-frequencyregime 267
6.1 Quasi-staticionization 268
6.2 Multiphotonprocessesinthestrong-fieldapproximation 281
6.3 Multiphotondirectionization 288
6.4 Highharmonicgeneration 305
6.5 Recollisionionization 320
6.6 Non-dipoleeffects 323
7 Thehigh-frequencyregime 334
7.1 High-frequencyFloquettheory 334
7.2 Structureofatomichydrogeninintense,high-frequency
laserfields 340
7.3 Atomicstabilization 350
PartIII Multiphotonatomicphysics 375
8 Multiphotonionization 377
8.1 Multiphotonsingleionization 377
8.2 Multiphotondoubleionization 398
9 Harmonicgenerationandattosecondpulses 418
9.1 Experiments 418