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High resolution two-photon spectroscopy of ¹²⁹Xe for precision optical magnetometry

University of British Columbia

This dissertation presents high precision two-photon xenon spectroscopy of the 5p₅(²P₃/₂)6p²[3/2]₂ ⟵5p⁶(¹S₀) transition. Specific attention is paid to the F = 3/2 hyperfine level of ¹²⁹Xe, motivated by the new experiment at TRIUMF to measure the electric dipole moment of the neutron. A non-zero value of the nEDM would partially confirm the existence of the baryon asymmetry in the universe as predicted by theories beyond the standard model. To achieve this measurement, ¹²⁹Xe is proposed for use in a cohabiting ¹⁹⁹Hg/¹²⁹Xe optical comagnetometer. To date, no laser system has existed to probe the specific xenon transition required for this measurement. We developed a novel continuous-wave 252.4 nm ultra-violet (UV) laser system with the power and precision to selectively probe the hyperfine levels of ¹²⁹Xe. Using this laser, we observed the first high resolution two-photon transition spectrum of xenon, which is comprised of ten transition peaks across the six most abundant isotopes, including the hyperfine levels of the ¹²⁹Xe and ¹³¹Xe. Detailed analysis of this spectrum revealed the hyperfine constants of the 5p₅(²P₃/₂)6p²[3/2]₂ excited state and other constants relating to the isotope shift. Furthermore, we describe initial observations into the pressure dependencies of the spectral lineshape from 15–980 mTorr. The ¹²⁹Xe pressure in the nEDM experiment is limited to 3 mTorr, making it essential to characterize the xenon signal at low pressures to maximize comagnetometer sensitivity. Intriguingly, our results suggest that ¹²⁹Xe qualitatively exhibits nonlinear pressure broadening at low pressure (<200 mTorr) - a phenomenon reminiscent of helium, neon and krypton. However, further investigation is required to fully characterize the pressure broadening effects in ¹²⁹Xe. Overall, these results define the expected signal lineshape and relative transition frequency to the F = 3/2 hyperfine level of ¹²⁹Xe for precision laser tuning. Collectively, this work contributes to optical magnetometry in nEDM experiments, as well as to precision spectroscopy and theories of atom-atom interactions.

Text

2019-10-21

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/72000

Physics

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/