A Guided-Beam Measurement of the Electron's Electric Dipole Moment

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This grant supports the development of a Ramsey double resonance apparatus using a coherently excited molecular beam of PbF to search for the electron's electric dipole moment (e-EDM). The current phase of the work involves precise spectroscopy of the transitions and states of the PbF molecule that will be used in the e-EDM search -- the hyperfine-resolved transition between the ground state X1(nu=0,J=1/2,+,|M|=1,F=1) and the excited state A(nu=0,J=1/2,+,M=0,F=1)). Specifically, we are making precision determinations of the energy of this transition and the effect of an applied E field to this transition. The latter measurement will determine the PbF molecular electric dipole moment to higher accuracy than currently known. We are also improving the stability of our laser system by using precisely characterized absorption lines in diatomic isotopic 130-Tellurium molecule. Future steps in this project include testing our entire measurement system along with our understanding of the Geometric Phase, an important systematic error in our proposed measurement, by constructing a molecular beam with an adjustable geometric phase. We will then show that we can predict, produce and measure this geometric phase for a specific configuration of electric fields.One of the profound puzzles associated with our understanding of the universe is the asymmetry between matter and anti-matter that is observed. Why is our universe made of matter and not anti-matter? A factor that affects this asymmetry is the shape of the electron as determined by measuring the electron's electric dipole moment (e-EDM). The possibility of such an e-EDM was first proposed by Purcell and Ramsey (Phys. Rev. 78, 807 (1950)) over 60 years ago. A new limit on the e-EDM was recently reported in Nature, 473,493 (2011) by a group at Imperial College, London. We are working on a similar, more sensitive, experiment to either set an even lower limit on this important constant or to more precisely measure it using PbF. We are in the preliminary phases of the planned experiment and this grant funds important spectroscopic measurements and equipment developments making an eventual e-EDM measurement possible.