High-precision spectroscopy and exotic nuclear structure

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This grant application support my group - currently consisting of 1 Research Associate, 4 PhD, 3 MSc, and 3 undergraduate students - in their research that is aligned along three major themes; development of the DESCANT detector at the TRIUMF-ISAC facility for neutron detection in both nuclear reactions with accelerated beams, and beta-delayed neutron measurements, nuclear structure studies to understand the origin and nature of collectivity in nuclei, and nuclear structure studies of nuclei important for fundamental symmetry tests and searches for physics beyond the Standard Model. DESCANT, a $2M CFI project, is an array of 70 deuterated benzene liquid scintillator detectors that can be used, in combination with the GRIFFIN gamma-ray spectrometer to take advantage of the new capabilities offered by TRIUMF with the development of the ARIEL facility that will provide intense beams of neutron-rich nuclei, many of which will have substantial beta-delayed neutron emission branches. When coupled to the TIGRESS gamma-ray spectrometer, it offers a sensitive channel selector for reactions induced by accelerated neutron rich beams. Our nuclear structure studies have probed the development of collectivity, mainly in the Cd region. Combining results from measurements of nuclear lifetimes with very-high-statistics beta-decay measurements enables a detailed mapping of collectivity. The Cd isotopes were believed to be some of the best examples of spherical vibrational motion, but our recent work has called this into question. We are extending our research into the region above Z=50, namely the Te and Xe isotopes, with high-statistics beta-decay experiments. Our investigations include studies with nucleon transfer and inelastic scattering reactions performed with the Q3D magnetic spectrograph at the Maier-Leibnitz Laboratory in Garching, Germany. In addition to the above investigations, my group has also been actively pursuing nuclear structure studies to support fundamental symmetry tests. Using the Q3D spectrograph, experiments were performed to test the accuracy of the structure calculations underlying the isospin symmetry breaking correction terms important in superallowed Fermi beta decay - used to derive the Vud element of the CKM matrix. A major new initiative undertaken is the investigation of nuclei in the vicinity of 199Hg with the aim of constraining models of the 199Hg Schiff moment. The most stringent limit on the existence of an atomic electric-dipole moment is that for 199Hg. Models of the Schiff moment of 199Hg have been hampered, however, by the lack of spectroscopic data, most notably of the E1, E2, and E3 strength distributions. In the first phase of our program, we are studying 198,200Hg via the inelastic scattering (d,d') reactions and single-neutron transfer into 199Hg. These studies will be extended to gamma-ray measurements via the (n,n'gamma) and (p,p'gamma) reactions.