High Precision Optical Spectroscopy and Quantum State Selected Photodissociation of Ultracold 88Sr2 Molecules in an Optical Lattice PDF
Preview High Precision Optical Spectroscopy and Quantum State Selected Photodissociation of Ultracold 88Sr2 Molecules in an Optical Lattice
Springer Theses Recognizing Outstanding Ph.D. Research Mickey McDonald High Precision Optical Spectroscopy and Quantum State Selected Photodissociation of Ultracold 88Sr2 Molecules in an Optical Lattice Springer Theses Recognizing Outstanding Ph.D. Research AimsandScope The series “Springer Theses” brings together a selection of the very best Ph.D. theses from around the world and across the physical sciences. Nominated and endorsed by two recognized specialists, each published volume has been selected foritsscientificexcellenceandthehighimpactofitscontentsforthepertinentfield of research. For greater accessibility to non-specialists, the published versions includeanextendedintroduction,aswellasaforewordbythestudent’ssupervisor explainingthespecialrelevanceoftheworkforthefield.Asawhole,theserieswill provide a valuable resource both for newcomers to the research fields described, and for other scientists seeking detailed background information on special questions. Finally, it provides an accredited documentation of the valuable contributionsmadebytoday’syoungergenerationofscientists. Theses are accepted into the series by invited nomination only andmustfulfillallofthefollowingcriteria (cid:129) TheymustbewritteningoodEnglish. (cid:129) ThetopicshouldfallwithintheconfinesofChemistry,Physics,EarthSciences, EngineeringandrelatedinterdisciplinaryfieldssuchasMaterials,Nanoscience, ChemicalEngineering,ComplexSystemsandBiophysics. (cid:129) Theworkreportedinthethesismustrepresentasignificantscientificadvance. (cid:129) Ifthethesisincludespreviouslypublishedmaterial,permissiontoreproducethis mustbegainedfromtherespectivecopyrightholder. (cid:129) They must have been examined and passed during the 12 months prior to nomination. (cid:129) Each thesis should include a foreword by the supervisor outlining the signifi- canceofitscontent. (cid:129) The theses should have a clearly defined structure including an introduction accessibletoscientistsnotexpertinthatparticularfield. Moreinformationaboutthisseriesathttp://www.springer.com/series/8790 Mickey McDonald High Precision Optical Spectroscopy and Quantum State Selected Photodissociation of Ultracold 88Sr2 Molecules in an Optical Lattice Doctoral Thesis accepted by Columbia University, New York, USA 123 MickeyMcDonald UniversityofChicago JamesFranckInstitute Chicago,IL,USA ISSN2190-5053 ISSN2190-5061 (electronic) SpringerTheses ISBN978-3-319-68734-6 ISBN978-3-319-68735-3 (eBook) https://doi.org/10.1007/978-3-319-68735-3 LibraryofCongressControlNumber:2017953964 ©SpringerInternationalPublishingAG2018 Thisworkissubjecttocopyright.AllrightsarereservedbythePublisher,whetherthewholeorpartof thematerialisconcerned,specificallytherightsoftranslation,reprinting,reuseofillustrations,recitation, broadcasting,reproductiononmicrofilmsorinanyotherphysicalway,andtransmissionorinformation storageandretrieval,electronicadaptation,computersoftware,orbysimilarordissimilarmethodology nowknownorhereafterdeveloped. Theuseofgeneraldescriptivenames,registerednames,trademarks,servicemarks,etc.inthispublication doesnotimply,evenintheabsenceofaspecificstatement,thatsuchnamesareexemptfromtherelevant protectivelawsandregulationsandthereforefreeforgeneraluse. Thepublisher,theauthorsandtheeditorsaresafetoassumethattheadviceandinformationinthisbook arebelievedtobetrueandaccurateatthedateofpublication.Neitherthepublishernortheauthorsor theeditorsgiveawarranty,expressorimplied,withrespecttothematerialcontainedhereinorforany errorsoromissionsthatmayhavebeenmade.Thepublisherremainsneutralwithregardtojurisdictional claimsinpublishedmapsandinstitutionalaffiliations. Printedonacid-freepaper ThisSpringerimprintispublishedbySpringerNature TheregisteredcompanyisSpringerInternationalPublishingAG Theregisteredcompanyaddressis:Gewerbestrasse11,6330Cham,Switzerland ToBartMcGuyer,whotaught mewhatit meanstobeascientist. Supervisor’s Foreword This is an exciting time for physics, and particularly for the field of atomic and molecular physics. Scientists can exert nearly perfect control over atomic motion andquantumstatesandusethisexquisiteprecisiontoseekanswerstofundamental questions. In recent years, there has been a surge in growth of cold and ultracold molecular science. Molecules are in many ways similar to atoms but offer greatly expandedpossibilitiesforunderstandingawidearrayofphysicalphenomena.This, of course, comes with new challenges, since even diatomic molecules have much morecomplicatedspectrathanatoms. Mickey McDonald’s thesis work unites studies of basic molecular quantum physicswiththehigh-precisiontechniquesofultracold-atomopticallatticeclocks. Hissophisticatedexperimentinvolvesmicrokelvindiatomicstrontiummoleculesin an optical lattice trap and utilizes optical spectroscopy to study physics near the atom-moleculethreshold.Mickeyobtaineduniquelatticeclock-stylespectroscopic measurements that clearly demonstrate the potential of ultracold molecule science and open the door to table-top tests of fundamental physics, such as molecular quantumelectrodynamicsandnanometer-scaledeviationsfromNewtoniangravity, atalevelthatwasnotpossiblebefore. Mickey’s thesis carefully demonstrates how forbidden transitions in molecules can be enabled with much weaker magnetic fields than in their constituent atoms, withimplicationsformetrologyandprecisionmeasurement.Italsodescribeswork on two-body subradiance, reporting by far the deepest subradiance to date, a 300- foldsuppressionofradiativeemission.Thisisafundamentaltwo-particlequantum optics effect, and it turns out that homonuclear diatomic molecules in an optical latticearetheidealsystemforstudyingitsproperties. Furthermore, Mickey’s thesis describes pioneering work on ultracold chem- istry via studies of molecular photodissociation. At extremely low temperatures, processes that create or break chemical bonds proceed according to quantum mechanical rules, and several approaches had been tried to observe these non- classical phenomena. In our lab, we had been detecting weakly bound molecules by fragmenting them into atoms, which were then imaged with a camera facing perpendicular tothe lattice trapping axis.Mickey was curious what would happen vii viii Supervisor’sForeword if we aligned a camera on axis with the lattice and looked at the photofragment angulardistributions.Soheledanefforttobuildthissetupandlearnhowtoprocess and interpret the images. The textbook-quality images shown in this thesis are beautiful pictures of diatomic molecules breaking apart in up to eight different directions, exhibiting coherent quantum mechanical patterns. This nonclassical behavior challenged intuition that was established before the 1980s. The thesis demonstrateshowtobreakmolecularbondswhileimpartingonlyaminisculelevel of excess energy to the fragments and thoroughly explores the cold regime from 100nKtotensofmillikelvin.Theresultsshowmatter-waveinterferenceofreaction productsaswellasquantummechanicalreactionbarriertunneling. Measuring ultralow temperatures, down to the nanokelvin level, is in itself an important outstanding problem, and Mickey’s thesis describes an invention of an excellent technique that relies purely on spectroscopy, thus yielding very high precision. It only requires the atoms or molecules to be tightly trapped in a lattice and to possess a narrow transition. Mickey uses this technique to characterize the temperature of ultracold strontium molecules and even to cool them down with a newtechniqueof“carriercooling.” The pioneering experiments described in this thesis set the stage for optical precision measurements with simple molecules at a level of quantum control that was previously impossible. With this new toolkit of controlling and measuring molecular properties at an unprecedented level, we can be sure to unlock many additionalmysteriesofmolecularandfundamentalphysics. NewYork,NY,USA TanyaZelevinsky July2017 Acknowledgments Writing a thesis can be a difficult, despair-ridden thing, marked by lonely nights and waves of self-doubt. And in the midst of this undertaking, it’s easy to lose perspective. In some ways, the thesis itself seems silly and ill-defined. Is it really possible to distill 6 years of life experience into 200 pages? Is that even the most efficient way to transfer knowledge? And who in their right mind would actually read such a thing? Should the thesis be a survey of the field? An original piece of unpublished research? A technical manual for the next generation of graduate students?Anopportunitytowaxpoeticonthemeaningoflifeandhowitallrelates toultracoldmolecules? Thefactisthatnoonetellsyouwhatthethesisissupposedtobe.Youjustwrite it, and hope that someone somewhere will find it useful. Such an open-ended task can be daunting, and I’ve found myself at times overwhelmed by the immensity of what lay before me. But as I write these acknowledgements, I’m sitting on a plane bound from Korea to New York, just getting back from presenting work at myeighthinternationalconference.Iliterallygetpaidtothinkabouthowtosolve the mysteries of the universe and interact daily with some of the smartest people on the planet. Objectively, I am incredibly fortunate. A physicist’s job is difficult, butatthesametimeitfeelslikeastretchtocalltheprofession“work.”My6years atColumbiahavebeenmarkedbyaconstantpursuitofanswerstoquestionsabout howtheuniversebehaves.I’mgratefultohavebeengiventheopportunitytoengage inthiskindofwork,becauseIknowhowrareitistobeabletogetpaidtodowhat youlove. When I first came to Columbia in the fall of 2010, I had the unfortunate com- binationofabigegoandzeroskills.AtmyfirstmeetingwithTanya Zelevinsky’s group, Tanya introduced me and asked for Gael Reinaudi and Chris Osborn (the group’s lead postdoc and first grad student respectively) to try and find something formetodo.AfteraskingwhetherIhadeverbuiltacircuit(“No...”),possessedany programming experience (“Matlab 101?”), or knew anything about lasers (“...at CornellIstudiedparticlephysics?”),Gaelsuggested“Well,perhapsyoucouldrest yourhandonthisstackofpapersandmakesuretheydon’tblowawayinthewind.” ix x Acknowledgments Despitethisominousbeginning,GaelandChriseventuallytookmeundertheir wings and showed me how to build lasers, run the experiment, and troubleshoot thorny problems. My success at Columbia wouldn’t have been possible without Gael’senthusiasmandChris’spatience.Iwasluckytoinheritanexperimentalready largelybuiltbythesetwogreatscientistsovertheprevious4years.Withoutthishead start,ourresultsoverthenextfewyearswouldn’thavebeennearlyasdramatic. NeartheendofChrisandGael’stimeatZLab,BartMcGuyercametoColumbia to take over leadership of the strontium experiment. After Chris left I became the senior grad student working on strontium, meaning that Bart and I would be collaborating closely. And whereas I had a fragile ego and was driven largely by passionandobsessioninchoosingwhatquestionstopursue,Bartwaslevelheaded andcareful,devotedtogettingthedetailsright.Hewasalso(muchtomydismay) clearlyquiteabitsmarterthanme. IrememberonceearlyinmytimeatColumbiagettingintosomephysics-related argumentwithBartandhavinghimclearlyandcalmly(butalsoquitebluntly)telling me exactly why I was wrong about some finer detail of the analysis of a recent experiment.Myfragileegowasonceagainsorelybruised,andaftertheconversation I basically stormed out to clear my head with a coffee and a breath of fresh air. AndIremembertalkingtoChrislateraboutthis,andcomplainingabouthowBart was totally unwilling to phrase his criticisms more delicately. To this he replied: “Mickey, I don’t think you realize how lucky you are to have Bart here as your postdoc.He’sarealscientist.”Ittookmeanotheryeartofullyappreciatethisfact, butInowseejusthowprescientChris’swordswere.Thisthesiswouldn’thavebeen possible without Bart, nor would I be half the scientist I am today without having hadhimherepushingmetobebetter.AsImoveontomyownpostdoc,IhaveBart’s exampletofollow,andcanonlyhopethatIcanofferthesamekindofmentorship to my own future graduate students as Bart did for me. And I hope Bart won’t be tooembarrassedwhenheseesI’vededicatedthisthesistohim. I’vehadthegreatpleasureofworkingwithaseriesofoutstandinghighschool, undergraduate, and master’s students during my time at Columbia, who indulged my(sometimespoorlythoughtout)curiositiesandinspiredmetothinkmoredeeply andtotryhardertounderstandwhatIdidn’tyetknowsowell.Highschoolsenior JenniferHahelpedmefinallyrealizeanoldideaforalecturedemonstrationofthe wave nature of light, leading to a paper we published in the American Journal of Physics[1].NoelWanandElijahuBen-Michaelspentcountlesshoursfiddlingwith prototypes for a crazy idea of mine for a “Laser-light intensity-insensitive passive polarization-stabilization setup (LLIIPPSS),” which was unfortunately doomed by subtlypersistentinterferenceeffects(butthanksforthegreatworkguys!).Matthew Miecnikowskihelpedrealizeanotherideaforanopticsexperimentwithpedagogical value:iffrequencyshiftsinacousto-opticmodulatorsareduetofirst-orderDoppler shifts from a diffraction grating moving at the speed of sound, is it possible to observesecond-ordershifts?(Onceagain,itturnedoutthatunfortunatelytheanswer was“No”...butwelearnedalot!)
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