Killian, Thomas C2019-05-162019-05-162017-082017-08-07August 201Camargo, Francisco. "Rydberg Molecules and Polarons in Ultracold Strontium Gases." (2017) Diss., Rice University. <a href="https://hdl.handle.net/1911/105495">https://hdl.handle.net/1911/105495</a>.https://hdl.handle.net/1911/105495In this work I describe the excitation spectra of Rydberg atoms in ultracold gases of strontium and their decay mechanisms. In a few-body regime, we observe a highly structured spectrum re ecting excitation of ultralong-range molecules consisting of one or more ground-state atoms bound to the Rydberg core in potential wells formed by the Rydbergelectron wave function. In a many-body regime, with hundreds of ground-state atoms within the Rydberg orbital, the Rydberg atoms can be viewed as an impurity in a quantum gas, connecting to important concepts in condensed matter physics. The spectrum for impurity excitation displays signatures of polaronic states, in which the Rydberg atom signi cantly perturbs the density of the background gas. Additionally, decay channels of Rydberg excitations are examined by monitoring the time evolution of Rydberg populations. The measured lifetimes reveal new information on the decay processes of Rydberg molecules and place limits on the time scales over which studies involving Rydberg species in cold, dense atomic gases can be undertaken and limit the coherence times for such measurements.application/pdfengCopyright is held by the author, unless otherwise indicated. Permission to reuse, publish, or reproduce the work beyond the bounds of fair use or other exemptions to copyright law must be obtained from the copyright holder.strontiumatomsultracoldgasBECpolaronrydbergmoleculeThesis2019-05-16