A few interesting publications

Here are two excellent articles related to Zach Etienne's colloquium




Selected Publications

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By Quinton McKnight, Adam Dodson, Tucker Sprenkle, Tyler Bennett, and Scott Bergeson
Abstract: We present measurements of the hyperfine splitting in the 173Yb 6s6p1Po1(F′=3/2,7/2) states that disagree significantly with those measured previously by Das and Natarajan [Phys. Rev. A 76, 062505 (2007)]. We point out inconsistencies in their measurements and suggest that their error is due to optical pumping and improper determination of the atomic line center. Our measurements are made using an optical frequency comb. We use an optical pumping scheme to improve the signal-to-background ratio for the F′=3/2 component.
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Abstract: We report on measurements of relative beta-decay rates of Na-22, Cl-36, Co-60, Sr-90, Cs-137 monitored for more than one year. The radioactive samples are mounted in an automated sample changer that sequentially positions the five samples in turn, with high spatial precision, in front of each of four Geiger–Müller tubes. The sample wheel, detectors, and associated electronics are housed inside a sealed chamber held at constant absolute pressure, humidity, and temperature to isolate the experiment from environmental variations. The statistical uncertainty in the count rate approaches a few times 0.01% with two weeks of averaging. Other sources of error are on a similar scale. The data are analyzed in variety of ways, comparing count rates of the various samples on one or more detectors, and comparing count rates of a particular sample across multiple detectors. We observe no statistically significant variations in the ratios of decay rates, either annual or at higher-frequency, at a level above 0.01%. 

Theses, Captstones, and Dissertations

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Dual-species ultra-cold plasmas in our laboratory expand too quickly for measurements at times longer than 30 microseconds. We plan to solve this problem by trapping the plasma using a Paul trap. The trap will be loaded by photo-ionizing neutral atoms in a co-located magneto-optical trap. This will enable plasma studies over longer time periods, making it possible to measure the internal interactions within the plasma. In order to use a Paul trap, we need to deliver higher voltages to the trap at radio frequencies. We report the successful construction of a harmonic resonator with a resonant frequency of ω = 2π ×4.0 MHz and a Q-factor of 151. When imperfect impedance matching is included in our measurements, we find that our helical resonator amplifies our radio frequency generator's output voltage by a factor of 120 at the trap.
Figure from thesis
A multi-laser approach is used in which we correct errors in the atomic spectroscopy that seriously compromised previous measurements by another group [Phys. Rev. A 76, 062505 (2007)].We report precision measurements of the 173Yb 6s6p1Po1(F′=3/2,7/2)transition frequencies. We use a frequency comb to determine the laser frequency. Our work completes a set of isotope- and hyperfine-shift measurements reported in [1], published by our group. The frequency shift between the 6s6p1Po1(F′=32,72)levels is 86.29±0.77 MHz. The uncertainty is dominated by quantum interference effects in the excitation and decay pathways. Appendix A is a summary of notes made on an overheating problem encountered in our laboratory, and a copy of both papers on which I was primary author while completing my undergraduate work included at the end of the thesis.
Figure from thesis
We create a dual-species ultracold neutral plasma (UNP) by photo-ionizing Yb and Ca atoms in a dual-species magneto-optical trap. Unlike single-species UNP expansion, these plasmas are well outside of the collisionless (Vlasov) approximation. We observe the mutual interaction of the Yb and Ca ions by measuring the velocity distribution for each ion species separately. We model the expansion using a fluid code including ion-ion friction and compare with experimental results to obtain a value of the Coulomb logarithm of Λ= 0.04.