Atomic fluorescence in a pulsed hollow cathode discharge with a copper vapor pumped dye laser

153 Pages·1991·4.6 MB·English

by  Womack, James Benjamin, 1964-

ATOMICFLUORESCENCEINAPULSEDHOLLOWCATHODEDISCHARGE
WITHACOPPERVAPORPUMPEDDYELASER
BY
JAMESBENJAMINWOMACK
ADISSERTATIONPRESENTEDTOTHEGRADUATESCHOOL
OFTHEUNIVERSITYOFFLORIDAINPARTIALFULFILLMENT
OFTHEREQUIREMENTSFORTHEDEGREEOF
DOCTOROFPHILOSOPHY
UNIVERSITYOFFLORIDA
1991
Dedicatedtomyparentsandgrandparents,whomadethe impossibleseem
possible,andtomyfriends,whomadetheimpossibleseemprobable.
ACKNOWLEDGEMENTS
The authorgratefully acknowledges the support ofCheryl Morgan, Edison
Becerra,and, especially,Dr.BenjaminSmith;theircontributiontothisworkwas
thoughtfullyappreciated.
IwouldliketothankthemembersofDr.Winefordner’sresearchgroup,past
andpresent. IwouldliketoespeciallymentionDr.JorgeVeraandDr.MarkGlick
forsharingtheirtechnicalknowledgeandDr.AnthonyMelloneforhisfriendship.
ManypersonalthanksgotoEricGessler,withoutwhoseenthusiasmforthe
project,technicalsupport,andpersonalfriendshipthiswouldnothavebeenpossible.
Personal thanks go to the division secretaries, Jeanne Karably and Susan
Ciccarone,fortheirpersonalfriendshipandtechnicalsupport;toRudyintheglass
shop;toChester,Vern,andtherestofthemachineshop;andtoSteveandMarkin
theelectronicsshop.
IwouldmostespeciallythankSharonStrainforherprofessionalandpersonal
contributiontothiswork. Herunendingpatience,moralsupport,andgoodhumor
wereinvaluable. Ithankyou,Shari.
Final acknowledgements go with my utmost thanks to Dr. James D.
Winefordner. Theopportunitytobeapartofthebestspectroscopygroupinthe
worldandtoworkwithsuchadistinguishedandfriendlyindividualwasthehighlight
ofmyacademiccareer.
iii
TABLEOFCONTENTS
page
ACKNOWLEDGEMENTS &
™
LISTOFTABLES
LISTOFFIGURES viii
ABSTRACT »
CHAPTERS
1 INTRODUCTION 1
NeedforUltratraceSensitivity 2
LaserExcitedAtomicFluoresenceforUltratrace
Sensitivity 3
TheGlowDischargeasanAtomizer 5
IntentofDissertation 8
2 HISTORICALDEVELOPMENTS 9
TheDevelopmentofAtomicFluorescenceSpectrometry 9
TheDevelopmentofAtomizerSystemTechnology 11
TheGlowDischarge 15
3 BASICTHEORYOFLASEREXCITEDATOMIC 22
FLUORESCENCE
TheoryofSingleStepAtomicFluorescence 22
BasicTheoryofLasers 31
Directionality 32
HighIrradiance 32
Monochromaticity 33
Coherence 33
TheCopperVaporLaser 34
IV
TheDyeLaser 37
NonlinearOptics 38
4 PRINCIPLESOFOPERATIONANDOTHERASPECTSOFTHE
GLOWDISCHARGE 42
BasicGlowDischarges 42
HollowCathodeDischarges 49
SampleSputteringintheHollowCathodeDischarge 51
5 EXPERIMENTAL 57
TheCopperVaporPumpedDyeLaserSystem 57
TheGlowDischargeAtomizer 61
HollowCathodeandVacuumChamber 61
ThePowerSupplyandPulsingSystem 64
TheFluorescenceCollection,SignalDetection
andProcessingSection 70
FluorescenceCollectionOptics 70
SignalDetectionandProcessing 70
SamplePreparationandAnalysisProcedure 71
SamplePreparation 71
AnalysisProcedure 72
PreparationofSolutionsandCleaningofGlassware 72
6 OPTIMIZATIONOFGLOWDISCHARGEPARAMETERS 74
SignalDependenceofVacuumChamberPressure 75
SignalDependenceonInjectedSampleVolume
andCathodeCupDiameter 80
SignalDependenceonDischargeVoltageand
Laser-GlowDischargePulseTiming 86
7 RESULTSANDDISCUSSION 102
ExperimentalDeterminationsofElements 102
TheDeterminationofLead 102
TheDeterminationofIridium 107
TheDeterminaitonofGallium 110
TheDeterminationofCobalt 113
TheDeterminationofIron 117
TheoreticalDetectionLimits 118
DeterminationoftheLimitingNoisesoftheSystem 124
v
8 CONCLUSIONSANDFINALCOMMENTS 126
REFERENCES 129
BIOGRAPHICALSKETCH 139
vi
LISTOFTABLES
7-
8-
4-1. PrimaryIonizationMechanisms 55
7-1. DefinitionsandParametersforEquation7.2 119
2. LimitingNoiseAnalysis 125
1. ComparisonofResults 127
vii
LISTOFFIGURES
2-
2-1. SchematicofOpticalLayoutofPierced
3- MirrorFluorescenceCollectionSystemwitha
3- GraphiteFurnaceAtomizer 14
4-2. SchematicDiagramofOpticalLayoutof
LEAFSinaHollowCathodeLampwiththeCuVapor
Laser 21
1. LasingDiagramforaCuVaporLaser 36
4-2. ConstructionofaHighPowerTunable
DyeLaser 40
5-1. DiagramRelatingDifferentTypesof
GaseousDischargesonTheirCurrentandVoltage
Characteristics. SectionAIsaTownsend
Discharge. SectionBIsaTransitionZone.
SectionCIsaGlowDischargewitha"Normal"
CathodeFall. SectionDIsaGlowDischarge
withan"Abnormal"CathodeFall. SectionE
IsanArcDischarge 44
2. DiagramShowingVariousLuminous
RegionsofaGlowDischargeBetweenTwoPlaner
ElectrodesandtheDistributionofVariousOther
PhysicalProperties 47
1. SchematicDiagramShowingthe
ExperimentalLayoutoftheLEAFSGlow
DischargeSystem 59
5-2. SchematicDiagramShowingthe
WaterCooledCathodeHolderandDisposable
GraphiteElectrode 63
Vlll
5-
5-3. SchematicShowingtheGlowDischarge
PulsingCircuit
6-
4. DiagramIllustratingtheLaserPulse
CausingaFluorescencePulse100pisAfterthe
GlowDischargePulse. TakenFromOscilloscope
MonitoringPMTDetector 69
1. PlotShowingDependenceofFluorescence
SignaltoVacuumChamberPressureforBothSolid
Leadand2ppmAqueousLeadDriedontheCathode 78
6-2. PlotShowingDependenceofFluorescence
SignalonSampleVolumeof2ppmLeadDriedin
theCathode 83
6-3. DiagramShowingIgnitionCharacteristics
fortheTwoDifferentSizeDisposableGraphite
ElectrodesUsed 85
6-4. PlotShowingDependenceofFluorescence
SignalontheAdditionof1000ppmAqueousSodium
toaSolidSampleofLead 89
6-5. PlotShowingtheDependenceofthe
FluorescenceSignalofaSolidLeadSampleon
DischargeVoltageforTwoDifferentLaser-Glow
DischargePulseSynchronizations. CurveA
RepresentstheLaserFiring35pisAfterthe
GlowDischargePulseandCurveBRepresents
theLaserFiring15pisAftertheGlowDischarge
Pulse 91
6-6. PlotShowingtheDependenceofthe
FluorescenceSignalonDischargeVoltagefor
a2ppmAqueousLeadSampleDriedontheCathode
withtheLaserFiring35pisAftertheGlow
DischargePulse 95
IX
6-7. PlotShowingtheDependenceofthe
FluorescenceSignalonDischargeVoltagefor
2ppmAqueousLeadDriedontheCathodewith
ThreeDifferentLaser-GlowDischargePulse
SynchronizationsataPressureof2Torr.
CurveARepresentstheLaserFiring16/is
AftertheGlowDischargePulse. CurveB
RepresentstheLaserFiring54/isAfterthe
GlowDischargePulse. CurveCRepresentsthe
LaserFiring75/isAftertheGlow
DischargePulse 97
6-8. PlotShowingtheDependenceofthe
FluorescenceSignalonDischargeVoltagefor
a2ppmAqueousLeadSampleDriedontheCathode
withThreeDifferentLaser-GlowDischargePulse
SynchronizationsataPressureof10Torr.
CurveARepresentstheLaserFiring16/isAfter
theGlowDischargePulse. CurveBRepresents
theLaserFiring54/isAftertheGlowDischarge
Pulse. CurveCRepresentstheLaserFiring
75/isAftertheDischargePulse 99
7-1. PartialGrotrianDiagramforLead 105
7-2. AnalyticalCalibrationCurveforLead 109
7-3. AnalyticalCalibrationCurveforIridium 112
7-4. AbsorptionSpectraforChlorobenzene
SolutionOpticalFilter 115
7-5. PlotshowingDependenceoftheFluorescence
SignalforSolidLeadontheLaserPulseEnergy.
ThisPlotIllustratesOpticalSaturationofthe
LeadFluorescence 122
x