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Taming Ultracold Rbsr and Sr2 Taming ultracold RbSr and Sr2 ACADEMISCH PROEFSCHRIFT ter verkrijging van de graad van doctor aan de Universiteit van Amsterdam op gezag van de Rector Magnificus prof. dr. ir. K.I.J. Maex ten overstaan van een door het College voor Promoties ingestelde commissie, in het openbaar te verdedigen in de Agnietenkapel op donderdag 6 september 2018, te 14.00 uur door Alessio Ciamei geboren te Rome, Italy ii Promotor: prof. dr. F.E. Schreck Universiteit van Amsterdam Copromotor: dr. B. Pasquiou Universiteit van Amsterdam Overige leden: dr.ir. S.J.J.M.F. Kokkelmans T.U. Eindhoven prof. dr. H.B. van Linden van den Heuvell Universiteit van Amsterdam prof. dr. W.J. Buma Universiteit van Amsterdam prof.dr. O. Dulieu Universite Paris Sud, CNRS dr. A. de Visser Universiteit van Amsterdam Faculteit der Natuurwetenschappen, Wiskunde en Informatica The research reported in this thesis was carried out at the Van der Waals-Zeeman In- stitute, Institute of Physics, University of Amsterdam. The work was financially sup- ported by European Research Council (ERC) under Project No. 615117 QuantStro, and the NWO through the Veni grant No. 680-47-438. iii \Omnis ars naturae imitatio est" Lucius Annaeus Seneca, Epistulae Morales ad Lucilium Liber VII, Ep. LXV v Contents 1 Introduction1 1.1 Motivation.................................1 1.2 Atoms vs molecules.............................2 1.3 State of the art...............................5 1.4 Which type of molecule?..........................6 1.5 Objective of this thesis...........................8 1.6 Overview of this thesis...........................9 2 Overview of the research 11 2.1 Context................................... 11 2.2 Experimental methods........................... 11 2.2.1 Preparation of ultracold atomic samples............. 12 Preparation of a single-species Sr sample............. 15 Preparation of a Rb-Sr mixture.................. 17 2.2.2 Preparation of quantum degenerate atomic samples...... 18 Bose-Einstein condensates..................... 18 Mott insulators in optical lattice................. 18 2.2.3 Experimental methods for molecule production......... 19 Photoassociation spectroscopy: one- and two-color resonance. 19 Magnetic spectroscopy: Fano-Feshbach resonances....... 22 Molecule production: STIRAP.................. 22 2.2.4 Atom detection........................... 23 2.3 Experimental setup............................. 24 2.3.1 Coil system............................. 24 2.3.2 Laser system............................ 25 2.3.3 Control system........................... 25 3 Efficient production of long-lived Sr2 molecules 27 Abstract...................................... 27 3.1 Introduction................................. 27 vi 3.2 Experimental strategy........................... 29 3.3 Theory.................................... 32 3.3.1 Model................................ 32 3.3.2 Parameter constraints....................... 32 3.3.3 Improving STIRAP efficiency................... 35 3.4 Experimental setup and creation of the Mott insulator......... 35 3.5 Molecule creation.............................. 38 3.5.1 Parameter characterization.................... 38 Rabi frequencies.......................... 38 Light shifts and loss by LFB;BB light............... 40 Light shifts from lattice light................... 41 3.5.2 STIRAP............................... 44 3.5.3 STIRAP with light-shift compensation.............. 46 Compensation beam........................ 46 STIRAP optimization and characterization........... 48 Effect of ∆, δ on efficiency and determination of γe ....... 52 3.5.4 Sample characterization...................... 54 Inhomogeneous light shifts by lattice light and dark state lifetime................. 54 Molecule lifetime.......................... 56 3.6 Conclusion and outlook.......................... 57 4 Observation of Bose-enhanced photoassociation products 59 Abstract...................................... 59 4.1 Introduction................................. 59 4.2 Experimental strategy........................... 61 4.3 Theory.................................... 64 4.4 Bose-enhanced Rabi frequency...................... 65 4.5 STIRAP parameters............................ 67 4.6 Molecule production............................ 69 4.7 STIRAP limitations............................ 71 4.8 Conclusion and outlook.......................... 72 5 1-color spectroscopy in ultracold Rb-Sr mixtures 73 5.1 Introduction................................. 73 5.2 Overview of 1-color spectroscopy..................... 73 5.3 Experiment................................. 76 5.3.1 Experimental setup......................... 76 Atomic sample........................... 76 vii PA laser setup........................... 77 5.3.2 Experimental methods....................... 79 Spectroscopy search........................ 79 Line characterization........................ 83 5.3.3 Analysis and Results........................ 85 5.4 Implications on STIRAP to weakly-bound ground-state RbSr............................. 90 6 The RbSr 2Σ+ ground state investigated via spectroscopy of hot & ultracold molecules 99 Abstract...................................... 99 6.1 Introduction................................. 100 6.2 RbSr state of the art............................ 102 6.3 PA spectroscopy of weakly-bound levels................. 104 6.3.1 Overview of two-colour photoassociation spectroscopy..... 104 6.3.2 Sample conditions and spectroscopy setup............ 105 6.3.3 Experimental results........................ 106 6.3.4 Data analysis............................ 108 Line attribution and estimation of physical quantities...... 108 Extraction of physical quantities.................. 110 Validation and inclusion of Fano-Feshbach spectroscopy..... 114 6.3.5 An independent check of quantum number assignment: inter- species thermalization....................... 116 Experimental setup and sample conditions............ 116 Measurement strategy........................ 117 Experimental results........................ 117 Extraction of collision cross sections................ 118 6.4 Thermoluminescence and LIF spectroscopy of deeply-bound levels.. 120 6.4.1 Experimental setup......................... 120 6.4.2 Simulations of the recorded spectra................ 121 6.4.3 Results............................... 122 6.5 Ab initio-based PEC fit.......................... 126 6.5.1 Statement of the problem..................... 127 6.5.2 Representation of the X(1)2Σ+ and B(2)2Σ+ state PECs... 127 6.5.3 Fit Method............................. 130 6.5.4 Results and discussion....................... 131 6.6 Conclusions and Outlook......................... 136 6.7 Appendix.................................. 138 6.7.1 Theoretical model for inter-species thermalization....... 138 viii 6.7.2 Potential energy curves...................... 139 7 Observation of Feshbach resonances between alkali and closed-shell atoms 145 Abstract...................................... 145 7.1 Main text.................................. 145 7.2 Methods................................... 151 7.3 Supplementary information........................ 154 7.3.1 Coupling mechanisms and resonance widths........... 155 7.3.2 Predicted Feshbach resonances.................. 156 7.3.3 Prospect for magnetoassociation................. 157 8 Outlook 159 8.1 Metrology and Precision measurements.................. 159 8.2 Few-body physics and ultracold chemistry................ 160 8.3 Many-body physics and quantum simulation............... 161 Bibliography 163 Summary 185 Samenvatting 187 List of publications 189 Acknowledgements 191 ix To B.C. 1 Chapter 1 Introduction 1.1 Motivation The interplay between quantum mechanics and interactions has had an unprecedented impact on the SI system of units and in fundamental science. Metrology will soon witness a revolution1 based on the redefinition of fundamental constants in terms of universal physical quantities. The kg mass artifact, the temperature of the triple point of water, the mass of carbon-12 and the vacuum permeability will be dropped in favor of the Planck constant, the Boltzmann constant, the Avogadro number and the elec- tric charge of the electron. In fundamental physics we have gained the interpretation of previously unexplained phenomena, e.g. black-body radiation, natural radioactiv- ity and superconductivity, and discovered new ones, e.g. blue-light emitting diodes, a self-sustained nuclear chain reaction, and the Josephson effect. Both metrology and fundamental physics benefit from the understanding of quantum-mechanical interac- tions. In many cases great effort is necessary to understand a composite system based on its constituents and the rules governing them. This happens because a system of many interacting particles can exhibit properties that are hard or even impossible to foresee by looking at its building blocks [1]. The result of such foundational work can ultimately enable important new applications, and it can do so in unexpected ways. Scale and complexity make strongly interacting quantum systems computationally intractable and motivate new theoretical and experimental methods. The complexity within atoms and molecules, the building blocks of chemistry and biology, is at present at the limit of our capabilities for accurate calculations from first principles. Experimental investigation of these systems has provided excellent understanding of their properties. Thus atoms and molecules represent our home base 1\The biggest revolution in metrology since the French Revolution", according to
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