CoulombExplosionImagingofMolecularFragmentationinFemtosecondPump-ProbeExperimentLOGANRINEY

MENTORS: DR. DANIEL ROLLES,

DR. ARTEM RUDENKO, ANDFARZANEH ZIAEE

AUGUST4, 2017

BriefOverviewØMotivationØExperimentalSetupØCoulombExplosionSimulationØResultsØConclusion

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MotivationØGoal:UseCoulombExplosionSimulationtomodeltherepulsionofionizedfragmentsofamolecule.

ØWouldliketoseeifCoulombExplosionImagingcandistinguishmolecularisomers.

ØThemoleculeofinterestiscis-,trans-dichloroethene

ØThismodelisusedtofindthekineticenergiesoftheionicfragmentsforagivenchannel

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cis-C2H2Cl2

trans-C2H2Cl2

ExperimentandSetupØSupersonicJetofC2H2Cl2 moleculesisdirectedintothebeampathtobephoto-ionized.

ØThemoleculesarephoto-ionizedby790nm,25fsnear-infraredlaserpulses

ØTheresultingfragmentsarethendirectedbytheE-fieldtotheiondetectortomeasuredbycoincidentionmomentumimaging.

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Intensity:4.25x1014 W/cm2

ExperimentandSetupØThedetectorcanmeasuretheTimeofFlight(TOF)ofeachion.

Ø𝑇𝑂𝐹 ∝ %&''()&*+,

�

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TimeofFlight(ns)

Coun

ts

ExperimentandSetupØThedetectoralsomeasuresphoto-ionsthatareincoincidence(PIPICO).

Ø ThediagonalstripesinPIPICOspectrumisduetoconversationofpzmomentaofcorrespondingcoincidentions.

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TOF1st ion(ns)

TOF2n

dion(ns)

CoulombExplosionSimulationØThefragmentpathsarecalculatedusingthe8th orderRunge-Kuttanumericalmethod.ØTheinitialconditionsforthemoleculeiscalculatedbyusingAvogadrotofindtheequilibriumgeometryforthedifferentbreakupchannels.

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D=3.251AD=2.171A D=2.171A

Angle=180°

CoulombExplosionSimulationØFortheC2H2

+ +Cl+ +Cl+channelthefollowingsystemwassolved:

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𝐹(./.0 𝑟2 ∝ 1𝑅266

+1𝑅286

𝐹(90 𝑟6 ∝ 1𝑅626

+1𝑅866

𝐹(90 𝑟8 ∝ 1𝑅826

+1𝑅866

Ø8th OrderRunge-Kutta giveshigherprecisionthanothercommonlyusedmethodslikethe4th OrderRunge-Kutta method.ØAsimilar,moresimplesetofequationsisusedtocalculate2BodyBreakups.

CoulombExplosionSimulationØAftersolvingasimilarsystem

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ResultsØTheCoulombExplosionsimulationworkswellforboththecis- andtrans- parentmolecule.

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Results:2Body- C2H2Cl+ +Cl+ØForcis-C2H2Cl2

ØTheinitialgeometrycalculatedbyAvogadro

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D=3.251A

Results:2Body- C2H2Cl+ +Cl+ØForcis-C2H2Cl2

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C2H2Cl+ Cl+ TotalKER

ExperimentalEnergy

2.3618eV 1.4028eV 3.7185eV

SimulatedEnergy

2.7979eV 1.6053eV 4.4032eV

Results:2Body- C2H2Cl+ +Cl+ØFortrans-C2H2Cl2

ØTheinitialgeometrycalculatedbyAvogadro

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D=3.251AD=3.466A

Results:2Body- C2H2Cl+ +Cl+ØFortrans-C2H2Cl2

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C2H2Cl+ Cl+ TotalKER

ExperimentalEnergy

2.2613eV 1.3026eV 3.5678eV

SimulatedEnergy

2.6198eV 1.5032eV 4.1230eV

Results:3Body- C2H2+ +Cl+ +Cl+

ØForcis-C2H2Cl2

ØTheinitialgeometrycalculatedbyAvogadro

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1.56A

3.22A

2.242A

Results:3Body- C2H2+ +Cl+ +Cl+

ØForcis-C2H2Cl2

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C2H2+ Cl+ Cl+ TotalKER

ExperimentalEnergy

7.012eV 5.113eV 5.063eV 15.000eV

SimulatedEnergy

7.147eV 5.154eV 5.154eV 17.455eV

Results:3Body- C2H2+ +Cl+ +Cl+

ØFortrans-C2H2Cl2

ØTheinitialgeometrycalculatedbyAvogadro

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D=2.171A D=2.171A

Angle=180°

Results:3Body- C2H2+ +Cl+ +Cl+

ØFortrans-C2H2Cl2

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C2H2+ Cl+ Cl+ TotalKER

ExperimentalEnergy

0.301eV 7.368eV 6.967eV 14.899eV

Simulated*Energy

0eV 8.312eV 8.312eV 16.624eV

*Thisisassumingthebondangleisexactly180°

ConclusionØCoulombExplosionImagingisausefultechniquetodistinguishmolecularisomers.

ØNumericalCoulombExplosionsimulationsagreewellwiththemeasuredkineticenergies.

ØBecausethesimulationusesaninstantaneouspulse,itgivesanupperboundtotheenergyreleasedfromtheCoulombExplosion

ØThereisacleardifferenceintheenergiesforcis- andtrans-dichloroethene andthismethodcaneasilydifferentiatebetweenthem.

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What’sNextØUsethissimulationtoinvestigateotherbreakupchannels.

ØImproveapproximationmethodforinitialconditionofthemolecules.

ØIntegratepulsewidthintothesimulation.

ØExpandCoulombExplosionsimulationtoworkfor4BodyBreakups.

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AcknowledgmentsØThankyouto:ØNSF

ØKansasStateUniversity

ØArtem, Daniel,Farzaneh,Kurtis,Utuq,andBalram

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Thankyou!QUESTIONS?

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References[1]Vager,Z.,Naaman,R.&Kanter,E.P.Coulombexplosionimagingofsmallmolecules.Science244,426–431(1989).[2] I.A.Bocharova etal., "Time-resolvedCoulomb-explosionimagingofnuclearwave-packetdynamicsinducedindiatomicmoleculesbyintensefew-cyclelaserpulses", Phys.Rev.A 83,013417(2011).[3]Ablikim etal.Identificationofabsolutegeometriesof cisand transmolecularisomersbyCoulombExplosionImaging. ScientificReports 6,Article number: 38202(2016).

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BackupSlides

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ExperimentandSetupØThischanneldenotesthatthereisdissociationoftheparentmolecule.ØCoincidentpairswillonlyoccurafteraCoulombExplosionevent.

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Dissociationchannel

Boundchannel