Toward Measuring a Charge-Parity Violating Electric Dipole Moment of the Electron: Production and Pseudo-Continuous Resonance Enhanced Multiphoton Ionization of

Abstract

Over one half century has passed since the possible violation of time reversal symmetry was proposed by Purcell and Ramsey. The Standard Model predicts that a value of the e-EDM |de,SM|<10-38e &middot cm that is beyond the reach of current experiment. At the same time, theories beyond the Standard Model predict an e-EDM at or near the current experimental level of $ |de,exp|< 1.3 &times 10-27e &middot cm. Thus an e-EDM is a great place look for physics beyond the Standard Model.

The existence of a permanent electric dipole moment would break the usual degeneracy between states of a molecule that only differ by the sign of the projection of their total angular momentum onto the axis of an external electric field. Heavy polar diatomic molecules are expected to be particularly sensitive to an e-EDM. Among the many proposed e-EDM molecules, the PbF molecule may be uniquely sensitive to an e-EDM because the magnetic moment of its ground state vanishes at a magic value of external electric field (67 kV/cm).

This thesis reports on the creation of a stable molecular beam source of PbF based on the serendipitous discovery of the reaction of lead vapor and MgF2 . This thesis also gives the result of the following achievements enabled by this source: (1) The first demonstration of resonant enhanced multiphoton ionization(REMPI) detection of the molecule. (2) Experimental measurement and analysis of the rotational spectra of the 0-0 band of the B &larr X1 transition of PbF. This measurement determines the rotational temperature of our source. (3) Measurement of appearance ionization from the B and D states of the PbF molecule. This measurement improves the known ionization potential of PbF from $7.5&plusmn0.3 eV to 7.54&plusmn0.01 eV, (4) Achievement of a multiphoton ionization probe of PbF that is doubly resonant with the A &larr X1 and D &larr A transitions. This scheme allows for fully state resolved spectra of the molecule. (5) Direct measurement of the lifetime of the PbF molecule. (6) Measurement of hyperfine constants that model the interaction of the unpaired electron in 208Pb19F with the 19F nucleus.

In addition to these achievements, a new type of ultra-sensitive REMPI is reported. Whereas conventional REMPI is typically carried out with pulsed laser systems, this new technique, dubbed pc-REMPI, occurs with a combination of continuous and pseudo-continuous lasers. This technique improves the detection sensitivity of the original PbF REMPI probe by a factor of 100. At the same time, the technique improves the spectra linewidth from 2 GHz to 90 MHz, allowing for full resolution of the hyperfine structure of the molecule.