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ANNOUNCEMENTS

SELECTINGANANALYTICALMETHOD

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TYPESOFERRORSINTHELABORATORY1.Randomerror•  Alwayspresent,alldirecHons•  OJenlimitsprecisionofmeasurements•  QuanHfy:standarddeviaHon2.Systema1c•  Affectsallmeasurementsinthesameway-DirecHonand

magnitude•  Assignablecause•  QuanHfy:bias

3.Gross•  Bigoops!•  Generallyclear•  Outliers?

ErrorFamilyTree

SOURCESOFEXPERIMENTALNOISEChemical•  Experimentsareaffectedbyuncontrollable

environmentalcondiHonsaffecHngsystem

Instrumentalnoise•  Affectsallcomponentsoftheinstrument

•  Observednoiseisacomplexcompositeofallnoise

sources

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SOURCESOFINSTRUMENTALNOISE

1.  Thermal/Johnson2.  Shotnoise3.  Flickernoise4.  Environmentalnoise

IMPROVINGS/NSTATISTICS

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LIGHT-MATTERINTERACTIONSCHEM314

•  ReviewelectromagneHcradiaHonandEMspectrum•  Wave-parHcleduality

•  Overviewofwayslightcaninteractwithmaaer•  ApplytheseinteracHonstothestudyofchemical

systems•  SummarizeexcitaHonandrelaxaHonwithinanatomor

moleculeusingaJablonskidiagram.

OBJECTIVES

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Spectroscopy?InteracHonbetweenlightandmaaer

ELECTROMAGNETICRADIATIONAamplitudepperiod(sec)νFrequency(sec-1;Hz)λWavelength(m-nm)vvelocityofpropagaHonwavenumber(1/λ;cm-1)Ppower(energys-1)Iintensity(Psolidangle-1)

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Whatisthefrequencyandenergyof500nmlight?

WAVELENGTH,FREQUENCY,ANDENERGY

WAVELENGTH,FREQUENCY,ANDENERGY

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ELECTROMAGNETICSPECTRUM

Wavenumber(cm-1)

Frequency(Hz)

Wavelength(m)

λ

ν

89.9x106HzPublicRadio Molecular

vibraHonsCoreelectronejected

NucleartransiHons

ElectronictransiHons

MolecularrotaHons

INTERACTIONSBETWEENLIGHTANDMATTER

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INTERACTIONSBETWEENLIGHTANDMATTER

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SUPERPOSITIONOFWAVES

INTERACTIONSBETWEENLIGHTANDMATTER

LIGHTASAWAVE•  DiffracHon

•  RefracHon

•  Transmission

•  ReflecHon

•  Scaaering

•  PolarizaHon

LIGHTASAPARTICLE•  Photoelectriceffect

•  AbsorpHon

•  Emission

•  Scaaering

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DIFFRACTION-BENDINGOFLIGHTASITPASSEDTHROUGHASLIT

Wavegenerator Wavegenerator

YOUNGEXPERIMENT(1800)-PROVEDLIGHTISAWAVE

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TRANSMISSION-TEMPORARYPOLARIZATIONOFMOLECULES

Atagivenfrequencyi:nirefracHveindexvivelocityofpropagaHoncspeedoflightinavacuum

RefracHveindex:

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DISPERSION-CHANGEINREFRACTIVEINDEXWITHFREQUENCY

Goodforlenses

Goodforprisms

REFRACTION-BENDINGOFLIGHTATINTERFACESOFMEDIA

Lessdense

Moredense

Lightbendstowardnormal

Snell’slaw

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REFLECTION-REFLECTIONOFLIGHTATANINTERFACE

hap://maxgrace.wordpress.com/2010/07/14/the-love-chapter-one-more-Hme/

SCATTERING-CHANGEINMOMENTUMOFEMRADIATIONRayleigh-elasHcscaaeringMie-largeparHclesRaman-inelasHcscaaering

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POLARIZATION-SELECTIONOFASPECIFICORIENTATIONOFEMRAD.

INTERACTIONSBETWEENLIGHTANDMATTER

LIGHTASAWAVE•  DiffracHon

•  RefracHon

•  Transmission

•  ReflecHon

•  Scaaering

•  PolarizaHon

LIGHTASAPARTICLE•  Photoelectriceffect

•  AbsorpHon

•  Emission

•  Scaaering

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PHOTOELECTRICEFFECT1.  Lightincidentonthe

photocathode2.  Electronsliberated3.  Voltageatanode

adjustedtostopcurrent4.  Stoppingvoltage

dependsoncathodesubstrateandradiaHonenergy

PHOTOELECTRICEFFECT

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ABSORPTION

ABSORPTION

CompareatomicandmolecularabsorpHon?WhydoesatomicabsorpHonoccuratdiscretewavelengthswhilemolecularabsorpHonoccurinbroadpeaks?

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EMISSION

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LUMINESCENCE

JABLONSKIDIAGRAM

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JABLONSKIDIAGRAMTRANSITIONSElectronicexcita1on-promo1onofanelectrontoanexcitedstate(electronic,vibra1onal,rota1onal).S0àS1

Nonradia1vedecay(vibra1onalrelaxa1on)-vibra1onalenergytransferredtoothermoleculesthroughcollisions.Veryfast.ExcitedstateàS1groundvibra1onalstate

Fluorescence-emissionofphotontoreturntoS0.S1àS0+hν

Internalconversion-radia1onlesstransi1ontoanextremelyvibra1onallyexcitedstateofS0withoutachangeinenergy.S1àS0

Intersystemcrossing-radia1onlesstransi1onfromS1toT1withnochangeinenergy.Changeofelectronspin.S1àT1

Phosphorescence-emissionofphotontoreturntoS0.T1àS0+hν

JABLONSKIDIAGRAM

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SCATTERING

Phenomena TimescaleTransmission 10-14-10-15sNonradiaHvedecay 10-15sElectronictransiHons 10-8sfluorescence 10-5sphosphorescence 10-5to100’ss

TIMESCALESOFTHEFOLLOWINGTRANSITIONS.

BASEDONTHESEOBSERVATIONS,CANYOUPREDICTWHICHTRANSITIONSMIGHTBEMORELIKELYTOOCCUR(ANDTHUSMORECOMMON)?

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LOOKINGAHEADTuesday(Jan26)-ProjectOverview(DueFeb15) LastdayforStandardAddi1on(DueFeb1)

Thursday(Jan28)-Beer’sLaw(Ch13,lookthroughderiva1ononwebsite)FirstdayofConsumerCharacteriza1onProjectExperiment1:MetalsAnalysisDue:Prelab1,Experiment1

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