Browsing by Author "Ding, Roger"

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    Narrow Line Cooling of 84Sr
    (2016-12-12) Ding, Roger; Dunning, F Barry; Killian, Thomas C
    Laser cooling has become a powerful tool for producing quantum gases and has enabled the study of a wide range of phenomena only accessible at ultracold temperatures. This thesis will describe the implementation and characterization of a magneto-optical trap (MOT) for laser cooling strontium to microkelvin temperatures operating on the narrow 689nm transition (the “red” MOT). The red MOT is the second cooling stage required to create quantum degenerate gases of strontium, bridging the temperatures and densities produced by the first cooling stage (the 461 nm “blue” MOT) and the shallow conservative traps for evaporation to quantum degeneracy.
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    Spectroscopy of ⁸⁷Sr Rydberg Atoms and Molecules
    (2019-09-16) Ding, Roger; Dunning, F B; Killian, Thomas C
    Spectroscopy of ⁸⁷Sr Rydberg Atoms and Molecules This dissertation describes the development of an apparatus to undertake spectroscopic studies of ⁸⁷Sr Rydberg states and their application in the production of ultra-long-range Rydberg molecules (ULRRMs). Most previous spectroscopic studies of strontium have been performed with the bosonic isotope ⁸⁸Sr which has no nuclear spin (I=0), resulting in a relatively simple and well-understood Rydberg excitation spectrum. In contrast, fermionic ⁸⁷Sr has a large nuclear spin (I=9/2) that leads to strong hyperfine interactions which greatly complicate the Rydberg excitation spectrum. In order to understand the Rydberg states in ⁸⁷Sr, two-photon spectroscopy was performed to measure and identify the (5sns)³S and (5snd)³D hyperfine Rydberg states for 30≲n≲99. Working with theory collaborators, a detailed understanding of how the hyperfine interaction affects the Rydberg levels is developed and used to extract revised quantum defects. The detailed understanding of the ⁸⁷Sr hyperfine Rydberg structure was exploited to produce the first ULRRMs in a fermionic gas. Unlike traditional molecular binding mechanisms, ULRRMs comprise of one or more ground-state atoms embedded in the electron cloud of a Rydberg atom with the entire system bound together through the weak Rydberg electron-neutral atom scattering. Therefore, production of ULRRMs is dependent on both the principal quantum number (n) of the parent Rydberg atom and the initial spatial distribution of atoms. At low temperatures, the effects of quantum statistics becomes important and result in bunching (bosons) and antibunching (fermions). These differences in spatial distributions can influence the excitation rates of ULRRMs. Current progress in exploring the role of quantum statistics in the excitation of ULRRMs using cold, dense strontium gases is described, with an emphasis on ⁸⁷Sr, and how such measurements can be used to extract the pair correlation function g⁽²⁾(R).