Physics
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Item Experiments with Ultracold Strontium in Compact Grating Magneto-Optical Trap Geometries(2022) Sitaram, Ananya; Campbell, Gretchen K; Physics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)In this thesis, we present the construction of a new apparatus for conducting experiments withultracold strontium. The new apparatus is designed with a high-flux atomic source, a custom science chamber optimized for optical access, high-current Bitter electromagnets, and an updated computer control system. We discuss in-depth the implementation of an insulated-gate bipolar transistor (IGBT) for fast current control of the magnetic field coils. We also present the design of JQI AutomatioN for Experiments (JANE): a programmable system on chip (PSoC)-based pseudoclock device that we use as the main clocking device for our experiments. Next, we report the realization of the first magneto-optical trap (MOT) of an alkaline-earth atom with a tetrahedral trap geometry produced by a nanofabricated diffraction grating. We have demonstrated a broad-line MOT in bosonic 88Sr and fermionic 87Sr. We trap approximately 4x10^7 atoms of 88Sr and achieve temperatures of around 6 mK, with a trap lifetime of around 1 s. Finally, we demonstrate sawtooth wave adiabatic passage (SWAP) in a narrow-line MOT of 88Sr atoms. In the narrow-line MOT, we trap approximately 3x10^6 atoms, with an average temperature of 3.4 µK and a trap lifetime of 0.77 s. We also discuss the possibility for a narrow- line grating MOT of the fermionic isotope. Our work with strontium grating MOTs is a step in the direction of compact quantum devices with alkaline-earth atoms.Item ISOTOPE SHIFT SPECTROSCOPY OF ULTRACOLD STRONTIUM(2019) Pisenti, Neal; Campbell, Gretchen; Physics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)We describe the design, construction, and performance of a laser system to probe the ultra-narrow (Γ/2π ≈ mHz) clock transition 1S0 → 3P0 in strontium. We present the first reported spectroscopy of this transition in two of the bosonic isotopes, 84Sr and 86Sr. Furthermore, we measure the complete set of isotope shifts between all four stable isotopes on the clock line and the narrow intercombination line 1S0 → 3P1, permitting a King plot analysis of the isotope shifts. Complications arising from the unambiguous determination of a line center in 87Sr 3P1 prevent us from making claims about the King linearity, but we provide a statistical boot- strap analysis of the isotope shifts 88−84Sr and 88−86Sr to compute a field shift ratio F698/F689 = 0.9979, with a 95% confidence interval [0.9952,1.0008]. The intercept term K698 − (F698/F689) K689 is similarly determined to be -2.0 GHz-amu, with a 95% confidence interval [−3.9, −0.3] GHz-amu. Finally, we describe the design of a next-generation apparatus that will enable improvements on the results described here, as well as other studies that involve coherent manipulation of strontium atoms on the clock line.Item Studies of Ultracold Strontium Gases(2017) Reschovsky, Benjamin; Campbell, Gretchen K.; Rolston, Steven L.; Physics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)We describe the operation and performance of an ultracold strontium apparatus that is capable of generating quantum degenerate gases. The experiment has produced Bose-Einstein condensates (BECs) of 84Sr and 86Sr as well as degenerate Fermi gases (DFGs) of 87Sr with a reduced temperature of T/TF = 0.2 at a Fermi temperature of TF = 55 nK. Straightforward modifications could be made to allow for isotopic mixtures and BECs of the fourth stable isotope, 88Sr. We also report on a technique to improve the continuous loading of a magnetic trap by adding a laser tuned to the 3P1 - 3S1 transition. The method increases atom number in the magnetic trap and subsequent cooling stages by up to 65% for the bosonic isotopes and up to 30% for the fermionic isotope of strontium. We optimize this trap loading strategy with respect to laser detuning, intensity, and beam size. To understand the results, we develop a one-dimensional rate equation model of the system, which is in good agreement with the data. We discuss the use of other transitions in strontium for accelerated trap loading and the application of the technique to other alkaline-earth-like atoms. Finally, we also report on an updated investigation of photoassociation resonances relative to the 1S0 + 3P1 dissassociation limit in bosonic strontium. Multiple new resonances for 84Sr and 86Sr were measured out to binding energies of -5 GHz and several discrepancies in earlier measurements were resolved. These measurements will allow for the development of a more accurate mass-scaled model and a better theoretical understanding of the molecular potentials near the 3P1 state. We also measure the strength of the 84Sr 0u transitions in order to characterize their use as optical Feshbach resonances.