Anapole Moment Studies in Francium

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The researchers will investigate aspects of the weak interaction, the force responsible for radioactivity, inside the nucleus of the least stable naturally occurring element, francium. Unlike the other three fundamental forces, the weak interaction does not act symmetrically in all circumstances. It behaves one way in one set of spatial coordinates, and another way when those coordinates are exchanged for a mirror image, a phenomenon called parity violation. The experiments will explore manifestations of this intrinsic handedness in different isotopes of francium confined in a laser trap and excited with microwaves. "Forbidden" (extremely rare) transitions by the atoms are linked to the presence of a peculiar shape of the current inside the nucleus, the anapole moment, that follows the surface of a bagel. To date this has only been observed in one isotope of cesium. Because the anapole moment is strongly affected by the number of neutrons that contribute to the parity-violating weak interaction, changing the isotope and repeating the experiment will allow measurements of parameters that characterize the weak interaction in the nucleus. This international effort, taking place at TRIUMF, the accelerator in Vancouver Canada, will allow two graduate students to be educated in the boundary between atomic, molecular and optical physics and nuclear physics. Local undergraduates will participate during the academic year; and in the summer Mexican students will take part through a program coordinated by the Sociedad Mexicana de Física.