Towards atomic parity violation at the francium trapping facility
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Date
2015
Authors
Collister, Robert
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Abstract
The development of the Francium Trapping Facility at TRIUMF, Canada and
progress towards an atomic parity violation measurement in francium are underway.
Francium (Z = 87) is the heaviest alkali. Its simple atomic structure and large
number of nucleons make it an attractive system for weak interaction studies. For
this reason, atomic parity violation in francium is an active area of study, and recent
years have seen significant progress towards that end.
Laser trapping of francium at Triumf has only recently been achieved, and several
useful physics measurements for the future atomic parity violation experiment
have been performed. The future measurement is of the highly forbidden 7S - 8S
optical transition amplitude, which is suppressed by ~ 10^10 compared to an allowed
transition amplitude. This will be achieved by interference with an allowed Stark
transition, similar to the 6S - 7S optical atomic parity violation measurement in
cesium. The commissioning of the two-chamber trapping apparatus as well as the
development of the electric field plates for the Stark interference will be reported on.
The physics measurements include the photoionization cross-section from the
7P_3/2 states, and isotope shifts of the D1 line. The cross-section must be known to evaluate a potential atom loss mechanism from the 506 nm light of the 7S - 8S
excitation, negatively impacting the trapped population. Atomic theory calculations,
which are required for the extraction of the weak coupling constants from the atomic
measurement, may be benchmarked against these isotope shifts, allowing theorists to
refine their techniques for the more sensitive evaluations.
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Keywords
Atomic parity violation, Francium, Atom trapping, Isotope shifts, Photoionization cross-section