Molecular spectroscopy, an enrichment diagnostic.

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Molecular spectroscopy, an enrichment diagnostic.

Laurent Bruel, Pascal Lemaire, A. Pailloux

To cite this version:

Laurent Bruel, Pascal Lemaire, A. Pailloux. Molecular spectroscopy, an enrichment diagnostic.. 15th

International Workshop on Separation Phenomena in Liquids and Gases (SPLG 2019), May 2019,

Wuxi, China. �cea-03255371�

第15届“液体和气体中的分离现象”

国际会议论文集

Proceedings of

the 15th International Workshop on

Separation Phenomena in

Liquids and Gases

曾实 周明胜 主编

Edited by Shi Zeng and Mingsheng Zhou

第15届“液体和气体中的分离现象”

国际会议论文集

Proceedings of

the 15th International Workshop on

Separation Phenomena in

Liquids and Gases

曾实 周明胜 主编

内 容 简 介 “液体和气体中的分离现象”国际会议每两年召开一次,为同位素分离领域的高水平学术会议之一。本书为第15届 “液体和气体中的分离现象”国际会议的科技报告文集。本书主题针对同位素分离的基础理论和技术,重点在同位素分离 的离心法和激光法,也包括其他分离方法和技术、同位素的应用等,反映了同位素分离领域中的理论研究和应用研究的新 思想、新进展。 本书可供从事同位素分离的科研技术人员和高等院校相关专业的教师以及研究生阅读参考。 版权所有,侵权必究。举报:010_-62782989,[email protected]。 图书在版编目(CIP)数据

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Proceedings

The15thInternationalWorkshopon

SeparationPhenomenainLiquidsandGases

May13-17,2019

Wuxi,China

EditedbyShiZengandMingshengZhou

Professor

DepartmentofEngineeringPhysics

TsinghuaUniversity

Beijing100084

China

Publisher:TsinghuaUniversityPress

PrintedinChina

􀅹 Copyright:

Allrightsarereservedbytheauthors.Nopartofthepapersintheproceedingsmaybereproducedin

anyformwithoutpermissionofthecorrespondingauthor(s).

Publ

isher’

s

Statement:

Theproceedingsarejustacollectionofthepaperspresentedonthe15thInternationalWorkshopon

SeparationPhenomenainLiquidsandGases(SPLG2019)andaremeantforacademicinformation

exchangeandstudy.Thatapaperispublishedintheproceedingsbynomeansimpliesthateitherthe

publisherortheeditorisfororagainstthepointofviewsoftheauthor(s),oranythingthatmaybe

inferredfromthepaper.Allpapers,forwhichthefullresponsibilityistakenbytheauthor(s),are

FOREWORD

AnotherSPLGWorkshop(the15thInternationalWorkshoponSeparationPhenomenainLiquids

andGases,SPLG2019)washeldinChinaduringMay13-17,2019,13yearsafterthe9thworkshop

(SPLG2006)and25yearsafterthe4thworkshop(SPLG1994).SPLG2019wasjointlyorganizedby

DepartmentofEngineeringPhysicsandWuxiResearchInstituteofAppliedTechnologies,Tsinghua

University.

TheSPLGworkshopisabiannualeventandhasahistoryof44years,iftakingthehistoryofits

predecessorintoaccount.ThepredecessorofSPLGisGSR_(WorkshoponGasesinStrongRotation),

whichwasorganizedsixtimes,respectively,inStockholm,Sweden(1975),Cadarache,France

(1977),Rome,Italy(1979),Oxford,UK(1981),Charlottesville,USA(1983),andTokyo,Japan

(1985).Then,ThenameofGSRwaschangedtoSPLGafterthe6thGSR.Sofar,fifteenSPLG

workshopshavebeensuccessfullyheldinDarmstadt,Germany(1987),Versailles,France(1989),

Charlottesville,USA(1992),Beijing,China(1994),Iguaçu,Brazil(1996),Nagoya,Japan(1998),

Moscow,Russia(2000),OakRidge,USA(2003),Beijing,China(2006),AngradosReis,Brazil

(2008),St.Petersburg,Russia(2010),Paris,France(2012),SanCarlosdeBariloche,Argentina

(2015),Stresa,Italy(2017),andnowWuxi,China(2019).Thetraditionaltopicsoftheworkshop

hadbeenisotopeseparation,butweregraduallyextendedtoawiderrangeoffieldstoincludeother

subjectsofresearchesconcerningvariousseparationphenomena,separationmethodsandtechniques,

providingaplatformofexchangingscientificideasandinformationforthepeopleoftheseparation

society.AverygoodreviewoftheSPLGhistorywasgivenbyProfessorWoodinhistalk“Historyofthe

SPLGWorkshops”inSPLG2017.ThepreviousGSRsandSPLGsaresummarizedinthefollowingtable:

Year Sites Participants Host Countries Papers Sessions

1975 Stockholm 37 20 9 22 5 1977 Cadarache 44 16 9 20 4 1979 Rome 70 22 10 28 6 1981 Oxford 70 15 10 26 6 1983 Charlottesville 67 40 10 24 6 1985 Tokyo 90 66 8 22 5 1987 Darmstadt 65 24 13 26 7 1989 Versailles 72 27 15 32 6 1992 Charlottesville 38 13 8 22 6 1994 Beijing 39 20 8 22 6 1996 Iguaçu 38 18 7 30 6 1998 Nagoya 90 62 9 48 6+3(para) 2000 Moscow 95 61 13 44 6+1(post) 2003 OakRidge 41 22 9 21 6

2006 Beijing 52 20 8 29(Oral)17(post) 8+1(post)

2008 AngradosReis 60 34 11 26 7

2010 St.Petersburg 102 66 16 53 5+1(post)

2012 Paris 107 40 16 37 9

2015 Bariloche 145 92 12 36 8+2(post)

Thecurrentworkshopintendedtocoverseventopics:

1.IsotopeSeparationbyCentrifugation;

2.LaserIsotopeSeparation;

3.OtherMethodsandTechnologiesofIsotopeSeparation;

4.NewMethodsandApplicationsofIsotopesandTheirAcquisition;

5.ProspectsandEconomicIssuesofSeparationMethodsandTechnologies;

6.NuclearNonproliferationandSafeguards;

7.PurificationMethodsandTechnologies.

Itattracted103participantsfromninecountries.Weweregladtoseethatthereweremanyyoung

researcherspresentingtheirresults,inadditiontotheolderexperiencedparticipantswithoutstanding

achievements.Therewere30oralpresentationsand14posterpresentations,includingsevenplenary

(special)talksgivenby,respectively,J.S.Tian,Z.H.Qiu,R.Snyder,V.D.Borisevich,

T.Mashimo,A.Lamagna,andJ.JakutisNeto.Someexcellentpresentationsgivenattheworkshop

areunabletobecollectedintheproceedings,unfortunately,becausetheauthorswereverystrict

abouttheirresults.WehopethattheywillbringtheirsatisfactoryresultsinthenextSPLGworkshop.

OnbehalfoftheInternationalOrganizingCommitteeandtheLocalOrganizingCommittee,we

wouldliketothankthestrongsupportfromAtomicEnergyIndustryCorporation,CNNC.Wewould

alsoliketothankallparticipantforattendingthisworkshopduringtheirbusytime.Wearevery

gratefultoProf.N.N.Chen,academicianofChineseAcademyofEngineering,Mr.J.S.Tian,

deputychiefengineerandtechniqueofficerofCNNC,andMr.Z.H.Qiu,chieftechnicalofficerof

AtomicEnergyIndustryCorporationofCNNC,whosparedtheirbusytimetoattendtheworkshop.

Prof.ShiZeng Prof.MingshengZhou

Chairman Co-Chairman

DepartmentofEngineeringPhysics

TsinghuaUniversity Beijing China September30,2019 · Ⅱ

INTERNATIONAL

ORGANIZING

COMMITTEE

Prof.SergeyBogovalov,NationalResearchNuclear

University(MEPhI),Moscow,Russia

Dr.DianeFischer,IAEA,Vienna,

Austria

Dr.AlbertoLamagna,ArgentinaNationalCommission

ofAtomicEnergy,BuenosAires,Argentina

Dr.PascalLemaire,CEA,BagnolssurCeze,

France

Dr.GiovanniMercurio,JointResearchCenter,

EuropeanCommission,Ispra,Italy

Dr.SylvanaPrestiMigliavacca,IPEN/CNEN-SP

andCTMSP,SaoPaulo,Brazil

Dr.AgnesPailloux,CEA/DIF/DASE,Arpajon,

France

Dr.Michael Whitaker,Oak Ridge National

Laboratory,OakRidge,USA

Prof.Houston Wood,UniversityofVirginia,

Charlottesville,USA

Prof.ShiZeng,TsinghuaUniversity,Beijing,China

LOCAL

ORGANIZING

COMMITTEE

Prof.DongjunJiang,DepartmentofEngineering

Physics,TsinghuaUniversity,Beijing,China

Prof.YongbinJiang,WuxiResearchInstituteof

AppliedTechnologies,Tsinghua University,

Wuxi,China

Ms.YunyanWang,WuxiResearchInstituteof

AppliedTechnologies,Tsinghua University,

Wuxi,China

Prof.ShiZeng,DepartmentofEngineeringPhysics,

TsinghuaUniversity,Beijing,China

Ms.RuiZhao,WuxiResearchInstituteofApplied

Technologies,Tsinghua University, Wuxi,

China

Prof.MingshengZhou,DepartmentofEngineering

Physics,TsinghuaUniversity,Beijing,China

CONFERENCE

CHAIR

Prof.ShiZeng,DepartmentofEngineeringPhysics,TsinghuaUniversity,Beijing,China

ORGANIZERS

DepartmentofEngineeringPhysics,TsinghuaUniversity

WuxiResearchInstituteofAppliedTechnologies,TsinghuaUniversity

SUPPORTERS

JointResearchInstituteforNuclearFuelCycleandMaterials,

TsinghuaUniversity—ChinaNuclearEnergyIndustryCorporation

ChinaNuclearEnergyIndustryCorporation,CNNC

· Ⅳ

CONTENTS

Ⅰ.

Laser

Technology

MolecularSpectroscopy,anEnrichmentDiagnostic(L.Bruel,P.Lemaire,A.Pailloux)……… 3

AdvancesintheArgentineProjectofUraniumIsotopeSeparationbyLaserTechnology

(A.Lamagna,P.D.Fainstein,D.Fregenal,P.Knoblauch,M.Zarco,J.D.Fuhr,J.Fiol,

E.Cortizo,E.Kaul,E.Santos,J.Gonzalez,N.Pachao,G.Berlín,S.Clavijo,E.Kirchuk)…………11

SelectivityinStudiesofLaser-inducedIsotopeSeparationinPulsedFreeExpansionsofSF₆and

UF6(D.Fregenal,P.Knoblauch,M.Zarco,E.Cortizo,P.D.Fainstein,J.D.Fuhr,

E.Kaul,A.Lamagna,P.Maceira,E.Zemma,J.Fiol)………24

SpatialDistributionofDysprosiumVaporGeneratedbyLaserAblationasaFunctionof

PulseEnergy(J.JakutisNeto,P.Bueno,A.A.Almeida,C.A.B.Silveira,K.K.Yum,

J.W.Neri)………30

ModellingforEstimatingTotalIonExtractionTimeofaBariumPlasmaUnderaParallel-plate

CollectorConfiguration(J.Chen,J.Li,H.P.Li,D.J.Jiang,M.S.Zhou)………35

Two-dimensionalSimulationofNear-longitudinallyPumpedDyeLaserAmplifiers

(Q.N.Yang,X.W.Zhang,Z.J.An,S.Zeng) ………40

ResearchonLight-inducedDriftAlkaliMetalIsotopeSeparation(J.Q.Yang,T.Liu,

J.D.Liu,C.Jin,Z.Z.Zhang) ………49

TheRubidiumEvaporationResearchinRubidiumIsotopeSeparationThroughthe

PhotochemicalMethod_(T.G.Yang,J.G.Jiang,S.W.Deng,L.H.Zhou)………57

Ⅱ.

Centri

fuges

DependenceoftheSeparativePowerofanOptimizedIguassuCentrifugeontheRotorParameters

(S.V.Bogovalov,V.D.Borman,V.D.Borisevich,I.V.Tronin,V.N.Tronin)………67

StudyoftheCirculationFlowinaCentrifugeDuringtheEnrichmentofIsotope

MixtureofHeavyGases(E.P.Potanin,L.Y.Sosnin,A.N.Cheltsov)………73

AMethodforAnalyzingtheTransientHydraulicsinaGasCentrifuge(S.Zeng,Z.G.Lei,

V.D.Borisevich,A.Y.Smirnov,G.A.Sulaberidze)………78

NumericalStudyontheEffectoftheFeedJetinGasCentrifuge(Z.Y.Gu,D.J.Jiang)…………86

StudyonEffectsofRotorWallPressureandWithdrawalFlowinaGasCentrifuge

(H.R.Chen,D.J.Jiang,S.Zeng)………91

StudyontheDiscWithdrawalChamberwiththeMolecularPumpInsidetheRotorfor

GasPurification(G.Pei,Y.B.Wang,D.J.Jiang,M.S.Zhou)………99

StudyonSeparativePerformanceofSingleCentrifugewithN-OctaneasMedium

NumericalStudyoftheHydraulicCharacteristicsoftheBi-directionallyConnectedGas

Centrifuge(M.An,Y.N.Zhang,S.Zeng,Z.G.Lei,V.D.Borisevich,A.Y.Smirnov)……110

StudyonPerformanceofInternalandExternalHolweckPumps(N.Y.Ling,D.J.Jiang,

Y.Sheng,X.Lu,C.L.Zhou,X.H.Li)………117

StudyofNumericalSimulationMethodoftheRadialSeparationEffectinthe

High-speed

RotatingFlowField(Y.Sheng,X.Lu,C.L.Zhou,N.Y.Ling)………121

ResearchonOn-lineActiveControlMechanismofRotorSidewallTemperature

(N.Y.Ling,X.K.Chen,L.Wang,R.Sun)………128

3DNumericalStudyontheGasFlowFieldandConcentrationFieldinaStrong

RotatingCylinder(X.H.Li)………132

Ⅲ.

Other

Separation

Technologies

ANewTypeofPlasmaCentrifugeforIsotopeSeparation(V.D.Borisevich,

E.P.Potanin,J.V.Whichello)………141

Electro-inducedSeparationofSolvatedIonsinSolutions(I.V.Shamanin,M.A.Kazaryan,

S.N.Timchenko,I.A.Ushakov,A.D.Poberezhnikov,H.D.Li)………147

StudyonBoronIsotopeSeparationbyGasDiffusionMethodUsingBF3asProcessingGas

(Y.B.Wang,G.Pei,M.S.Zhou) ………156

Ⅳ.

Centri

fuge

Cascades

&

Stable

Isotopes

SeparationofMulticomponentIsotopeMixtureDuringFillingofGasCentrifuge

Cascade(A.A.Orlov,A.A.Ushakov,V.P.Sovach)………165

ReprocessedUraniumEnrichmentforSustainableNuclearFuelSupply

(A.Y.Smirnov,V.E.Gusev,G.A.Sulaberidze)………175

ObtainingHighlyEnrichedIntermediateIsotopesinCascadesofGasCentrifugeswith

AdditionalProductFlows(A.Y.Smirnov,D.N.Fomin,S.Zeng,G.A.Sulaberidze,

A.R.Mustafin,V.D.Borisevich,D.J.Jiang) ………183

EconomicAnalysisofHighAbundance10BIsotopeProductionbyCentrifugalMethod

(C.H.Jian,J.X.Pan,Q.M.Sun,G.Pei,M.S.Zhou) ………190

TechnologyResearchforSeparationofSilicon-28IsotopeProductionbyaGasCentrifuge

(D.D.Dou,Y.K.Cong) ………196

StudyontheEffectofTailAbundanceonCentrifugalCascadeEfficiencyand

ItsControlMethod(Z.Y.Zhang,H.W.Wu)………203

ApplicationofGeneticAlgorithminCascadeOptimization(H.T.Yao,M.Zhang,Y.Liao)……208

ResearchontheCalculationMethodforImprovingConformityoftheCascadeScheme

(F.Zou,J.Chen,T.Pan,L.Z.Zeng)………219

DefinitionofStaticCharacteristicRootsofaCentrifugalCascade(W.J.Li,

Z.D.Wu,H.Yan)………225

ApplicationofSimulationinCascadeFaultDiagnosis(H.Yan,W.J.Li,C.Q.Ge)………232

StudyMeasurementandOptimizationofOperationParametersofaCentrifugal

Cascade(J.X.Gan,B.Qiu)………239

· Ⅵ

AnalysisofResponseandFactorCorrelationBasedonComplexEquipment

PerformanceData(C.L.Zhou,X.Lu,Y.Sheng,R.L.Wang)………248

StudyonUnsteadyStateofLowAbundanceCentrifugalCascade(Z.H.Liu,Z.Y.Zhang) ……258

NumericalStudyontheProcessofUF6DesublimationinaTank(Y.N.Feng,D.J.Jiang)………264

ListofParticipants………270 AuthorIndex ………275 · Ⅶ · CONTENTS

Molecular

Spectroscopy,

an

Enrichment

Diagnostic

L.Bruel1,*_,P.Lemaire1_,A.Pailloux2

1.DepartmentofEnrichmentTechnologies,Dismantling&Wastes AtomicEnergyCommission,France

*Correspondingauthor,Email:[email protected] 2.DepartmentAnalysisSurveillance,Environment

AtomicEnergyCommission,France

Abstract

InMolecularLaserIsotopeSeparationprocesses,high-resolutionspectroscopyiscommonlyusedto

determinetherotationalandvibrationaltemperatures.

InbothversionsoftheMLISprocesses(dissociationorSILEXversion),thejet-cooledgastendsto

formrapidlyvanderWaalscomplexeswiththeraregasusedascarriergas.Thesephenomenaare

importantforisotopicselectionastheyinitiatethecondensationphenomena.

IncaseofSF6,smallheteroclusters(SF6-raregas)areinvestigatedwithrovibrationallaserjet-cooled

spectroscopyintheν3region(10μmforSF6),forsomeraregasatom(RG).High-resolutionspectra

aremeasuredforboththeperpendicularandparallelbandsforNe,Ar,KrandXeheteroclusters.It

isshownthatthereducedvibrationalredshiftsareindependentoftheRGatom,leadingustoagood

understandingoftheirconformation.

InthecaseofUF₆,theunusualwavelengthoftheν3bandrequiredthedevelopmentofaspecificDFB

laserat16_μm.ThishasbeendoneatIES_{(CNRS/University}ofMontpellier)usingtheInAs/AlSb

quantumcascadelaser(QCL-DFB)technologythatdemonstratedroomtemperatureoperationin

continuousregimeforthefirsttimeabove16_μmwithalinewidthofafewMHz.

AbsorbancemeasurementswiththeselasersarenowdemonstratedonisolatedNH3linesinthe16μm

range,atlowpressure.Thermalinducedfrequencymodulation(2f/f)isusedtoimprove

signal-to-noiseratio.

Inthecaseofonlineisotopicratiosmeasurements,thislasercouldmeasuretheUF₆moleculenumber

densityofbothisotopologues.Forthatpurpose,itwillbecoupledtoanintegratedpulsedsupersonicjet.

1.

Introduct

ion

Severalteamshavestudiedtheabsorptionspectrum

oftheν3vibrationofUF6.Takamietal.[1]have

evenpublishedverydetailedspectralportionsto

isolatetheQbranchof235UF6betweentheR(5)

andR(6)linesof238UF6inapulsedsupersonic

jet.Toavoidhotbands(multiexcitedvibration

withν3)andbringallthemoleculesintothe

groundstate,theUF6plusbuffergasmixture

shouldbecooledtobelow50Kinanadiabatic

expansion.Atthesetempera-turesvanderWaals

complexesappear.Theyaretheproductof

homo-geneousorheterogeneousaggrega-tionofUF6,with

thebuffergas,markingthebeginningofcondensation.

Thespectroscopytechnicthatwehaveimplemented

allowsustoidentifythedifferentstatesofthe

gasintheexpansion,eitheronasimulantofthe

molecularstructure,theSF6,orontheUF6,

accordingtotheavailable Quantum Cascade

Laser(QCL)diodes(10_μmor16_μm).Wereport

herethedetailedspectro-scopicresultsforSF6,

conductedwithapulsedgasexpansion,andalsoa

continuousjet.Thefirstparagraphfocuseson

aerodynamicresults—temperaturemeasurements—in

continuous

relaxa-tion.Thenextidentifiesdimers

andclustersbandsversusthebuffergastype.The

thirdwilldealwithQCLperformanceat16_μm.

Thelastparagraphwillconcludetheuseofthis

diagnosticinisotopicseparation.

2.

High-resolution

spectroscopy

of

UF

for

aerodynamic

2.1 Theoreticalcalculations

Toperformasufficientspectralidentificationin

theinfraredregionwithinabroadspectralrange

atveryhighspeeds,onlytheabsorption

spec-troscopywithQCLlaserdiodeispossible.Now

thatitisfeasible,itwasnecessarytobeableto

comparethespectrawiththetheorytodeduce

veryaccuratelythevibrationalandrotational

temperatures.Fortunately,thecoldband of

UF₆ canbecalculatedusing Highly-spherical

TopDataSystem(HTDS)software[2].

Calculatedtemperaturedependenceofthespectrais

verystrongforUF₆asshownonFigure1andon

Figure2,forrespectively20 Kand10 K;on

Figure3isshownthesuperpositionof235_UF

6and 238_UF

6at1K.Evenwithanisotopicshiftof

0.65cm-1_{,thetwosetsofrotationallinesare}

notseparated.Thankstohighresolution

spectro-scopy,mostoftherotationallinescan be

separated.

Figure1:235_UF

6and238UF6coldbandsat20K

Figure2:235_UF

6and238UF6coldbandsat10K

· 4

Figure3:Inorange,235_UF 6

rotationallinesareinsidetherotational structureof238_UF

6,inblue

2.2 Rotationaltemperaturemeasurements

WhenweuseSF₆tosimulateUF₆ wemustbe

awarethattheisotopicshiftsarereallydifferent,

asyoucanseeonFigure4 whereallsulfur

hexafluorideisotopologuesareseparatedatall

temperatures.Nevertheless,SF6isavalidating

tooltointerpretphenomenarelativetoeither

aerodynamicoraggregation.

Figure4:ν3vibrationofthe34SF6 33SF

6 32SF

6

isotopologuesrespectively

Thewaytogetverygoodtemperature

measure-mentsisasfollows.Acomparison

theory/experi-mentisperformedforallrotationaltransitions

(Figure5)andthebestfitgivestherotational

temperature.Onthisgraph,realizedwithalaser

resolutionof20MHz,thecalculated(HTDS)and

measuredspectraareinaverygoodagreement

evenatthelinelevel.Therotationaltemperature

canthenbededucedwithaprecisionoflessthan

±5K.

Figure5:TheoryandexperimentagreementontheRsideoftheν3vibrationofSF6,at20MHzresolution

2.3 Vibrationaltemperaturemeasurements

Hotbandsinvolveothervibrationallevelsdepending

onvibrationaltemperature.Hotbandsappearasthe

vibrationaltemperatureincreases.Weusethemto

measurethattemperature,ashotbandspopulationis

linkedtoit.AssumingBoltzmandistribution,thetwo

Qbranchsurfacescangiveanestimationofthe

expectedtemperature.

· 5 ·

Figure6:ν3bandsat100Kvibrationaltemperatureand

at20Krotationaltemperature,hotbands(inred)are visible(forinstancehereinvolvingν5bandsvibration

at946.9cm-1₎

3.

SF

-Rg

spectroscopy

(clusterization)

Thedifferentconfigurationsofaggregates

(hom-oclusters,heteroclusters)inthedifferent

aero-dynamicregimes,partialconcentrationsorgas

laserinteractionsmustbeunderstoodtochoose

theoperatingpointofalaserisotopicseparation

process.

Aggregatehigh-resolutionspectroscopyhasbeen

successfullyinvestigatedfortheν3vibrationwith

thepulsedjetexperimentofMONARISinJussieu

University[3].Experimentshavebeencarriedout

withdifferentraregases(Rg).

3.1 SF6-Rgheteroclusters

TheparallelandperpendicularbandsofSF6-Rg

heteroclustershavebeenidentified.Thesebands

arisefromthedegeneracyliftingofthetriply

degeneratestate(ν3)oftheSF6monomer.

Theseexperimentalspectraareveryweakcompared

tothestrongmonomerband.But,thankstothe

accuracyofthecalculatedmonomerband,the

heteroclustersbandisobtainedbysubtractingthe

theoreticalspectrumfromthemeasurement(in

greenonFigure7).

Theseclusterspectrahavebeensuccessfullycomputed

andtheexperimentalspectralshiftsareingood

agreementwiththepredictionbasedona

Buckingham-typepotential.Somemolecularparametersofthis

model(rotationalconstants,bandcentersand

S-Rgdistances)have been deductedfrom the

measurements[3].

3.2 (SF6)2-dimer

Thefirstconformerof(SF6)2,(band#1),has

beenpublishedin1995byUrbanandTakami.A

secondconformer(band#2)hasbeenidentified

recently[3].

Figure7:EC-QCLjetcooledpinholespectraofbothν3parallelbandsofSF6-Rgheterodimers

(Rg=Ne,Ar,Kr,Xe)with0.12%SF6and1%Rgdilutedin8barheliumatanaxialdistancez=15mm

· 6

Again,withtheexperimentaldata,theyhavebeen

simulatedbysymmetrictoptransition,takinginto

accounttheirsymmetriesD2dandC2handtheir

temperaturesof3Kand8Krespectively(Figure8).

Temperaturesaredistinctbecause#2isformed

duringearlyexpansionathighertemperature.A

collisionalrelaxationprocessleadstopopulation

conversionfromdimer#2todimer#1.

Figure8:Parallelbandsoftheconformations#1and#2ofthedimer(SF6)2,summation

comparedtoexperimentalspectrum

3.3 (SF6)2-Rgheteroclusters

WhenthestructureofthehomodimerSF6waswell

understood,thecontinuationoftheheterogeneous

aggregationinthemixturesupersonicexpansionwas

studied withseveralraregases,fordifferent

geometries(slitornozzle),SF6concentration,

axialprobedistance.

The#3band(inredFigure9)waseasilyassignedto

theheterocluster(SF₆)₂-Rg,becauseoflinear

de-pendenceofthevibrationalshiftbetween#2and

#3bandswithgaspolarizability.

Thislineardependenceisshowingthatthetrimer

#3configurationisthesameas#2.Thisil

lu-stratesthelackofrobustnessofthe#1dimer,

owingtoexternalperturbations,likecollisionsor

complexationwithaHeatom.

Finally,theseresultsshowthatitisnecessaryto

usesophisticatedapproachestosimulatethese

systems[4].

Figure9:Spectraofdifferentheteroclusters(SF6)2-Rg

forRg=HetoXe,lineardependenceofthevibrational shiftwiththepolarizabilityoftheraregasatomisshown

· 7 ·

4.

QCL

a

tool

for

high-resolut

ion

spectroscopy

Alltheseexperimentshavebeendoneusingthe

pulsedjetSPIRALESbenchinParisoronthe

continuousjetinourlab,withthesameexternal

cavityQuantumCascadeLaseratawavelengthof

10μmfromacommercialsupplier.

Theenergydomainofthevibrationsandthe

isotopicdifferencesareweakerforUF6,which

willmodifythebehavioroftheaggregatesinthe

relaxation,thehigh-resolutionspectroscopywillmake

itpossibletounderstandthebehavioralchanges.To

investigatethehigh-resolutionspectroscopyofUF6,

thereis(in2019)nocommercialdeviceavailableatthe

wavelengthof16_μm.

ThankstoacollaborationwiththeInstituteof

ElectronicsandSystems(IES,CNRS/University

ofMontpellier)inFrance,thethefirstworldCW

16μmlasersource[5,6]operatinguptoambient

temperaturehasbeendevelopedintheUniversity

ofMontpellier.Weusedoneofthesesourcesin

thisstudy.Thislasercanacceptnotonlycontinuous

regime,butitalsotolerateroomtemperature

regimeatthesametime.Itcandeliver50mW

CWforapproximately7Wofelectricalpower.

QCLsaredifferentfromlaserdiode(Figure10)

astheyusemanycurrentinjectorsinseriesconnected

byaquantumtunneling.Eachinjectorprovides

onephotonfromthesameelectron.Thegaincan

behigh,dependingonmaterialsanddesign.

Thewavelengthisfirstobtainedbyadjustingthe

designofthegainstructurewhichisanepitaxed

multilayer,withaBragggratingetchedontopon

theridgetoobtainamonomodeemissionlinewidthof

afewMHz.

InAsisadvantageouslyusedathigherwavelength,

thankstoitselectron’sloweffectivemass,andit

hasbeenextendedinthefarIR(upto25_μm).

OnthecontraryInPisnotsuitablebecausethe

substrateisabsorbingverynearto_16μm,duetoa

phononresonance.

Figure10:AlSb/InAsactivezone(AlSbtunnel~1Åto 100Å),Oneperiod=20MoCVDlayersNp=144periods

(7_μmthick)

4.1 TheuseofQCLat16_μm

Duetothermaleffects,theemittedwavelength

dependsonbothtemperatureandcurrent.Itisthen

possibletoscana1.5cm-1rangebyvaryingthe

current,andscana6cm-1_{rangebychangingthe}

operatingtemperature,asshownonFigure11.

Figure11:Exampleofcurrenttunablityatfixed temperatureofourQCLship

4.2 LasertestonNH3gascell

Asimpletestonalow-pressureammoniacellhas

beenconductedtoconfirmthatthislasersourceis

usableforUF6spectroscopy.

Linewidthwasfoundlessthan30MHzandthe

lasercouldeffectivelyscanfrom627to634cm-1

byvaryingthetemperature(Figure12).

4.3 2f/fdetectionfromlasermodulation

Inadditiontoasmallsize,alargepowerat16_μm,

averyhighspectralresolution...,theQCLcanbe

modulatedatamaximalfrequencyof100kHz.A

synchronousdemodulationwithdetectionofthe

firstandsecondorderspermitsustoincreasesignalto

· 8

noiseratio,usingtheso-called2f/ftechnic.

Figure12:Experimentalscanfrom627to634cm-1_witha16

μmQCLaser.Theredarrowindicateswhere thecentralpositionofthe235_UF

6linesisontheammoniaspectrum

Figure13isanumericalsimulationwithnoisy

signalscomingfromthe235_UF

6 branch HTDS

calculusandmodulationofthelaser.Thendetection

ofthefirstandsecondordersisundertaken.

Comparedtodirectabsorption,wherethesignals

areblurred,thedemodulatedsignalsareclean.

Thistechnicisanecessarytooltoobtainthehigh

dynamicneededtoacquirebothisotopesatlow

assay.

Figure13:Simulationofnoisysignalsdemodulatedusingthe2f/fschemecomingfromthe235_UF 6

branch(redandgreen)tobecomparedtodirectabsorption(ingrey)

5.

Conclusions

MLIS-typeisotopicseparationtechniquesareknown

tobepotentiallyprofitable,thatistosaywith

highselectivityandwithaccesstotheentireUF6

population,onlyinvolvingisentropicexpansion

carryingthegasmixtureatverylowtemperature.

However,duringtherelaxation,adimerization

followedbyhomogeneousorheterogeneous

aggrega-tionarisesaccordingtotheconditionsofthe

process.Toproperlycontrolthethermodynamic

· 9 ·

stateofthegasmixture,spectroscopyproveshere

tobethebesttool.Athighresolutionitdiscriminates

thetypesofaggregates,andforaprocessmonitoring,

itdiscriminatestheisotopes,eveniftherovibrational

spectraarenested.ForUF6,thewavelengthofthe

characteristicvibrationisinthefarinfraredandthe

onlytoolwiththisdiscriminantpotentialistheQCL

laserdiodethatweusedinthisstudy.

Acknowledgements

Thisworkhasonlybeenpossiblethankstothe

followingpeopleandinstitutes:

M.A.Gaveau,M.Mons,V.Brenner(LIDYL,CEA,

CNRS,UniversitéParis-Saclay,CEASaclay,91191

Gif-sur-Yvette,France)

P.Asselin(SorbonneUniversités,UPMCUniv.Paris

06,UMR8233,MONARIS,F-75005,Paris,France)

V.Boudon,(LaboratoireInterdisciplinaireCarnotde

Bourgogne,UMR6303CNRSUniversité)

A.C.Turner(DepartmentofEarthandPlanetary

Science, University of California,Berkeley,

California94720USA)

A.Potapov(LaboratoryAstrophysicsGroupof

theMaxPlanckInstituteforAstronomyatthe

FriedrichSchillerUniversityJena,Germany)

R.Teissier,A.N.Baranov(CNRS&Univ.

Mont-pellier,IES(InstituteofElectronicsandSystems),

UMR5214,F-34000,Montpellier,France)

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