A three-year research program involving nuclear scientists from the University of Dallas, the United States Naval Academy, and the University of Kentucky is proposed. This program is designed to include active participation by undergraduate students in the research effort. The experiments will be conducted at the University of Kentucky Van de Graff laboratory using the (n,n'y) reaction mechanism. The focus of this research is the study of mixed-symmetry, or isovector, collective excitations in the N=84 and Z=52 vibrational nuclei. The specific nuclei planned to study are 142 Ce, 144Nd and 120, 122Te. Fragmentation of the quadrupole isovector strength will be explored. Considerable spectroscopic information will be ascertained in achieving this goal since M1 and E2 transition rates and E2/M1 multipole mixing ratios are required to interpret the mixed-symmetry character of ollective quadrupole levels. Transition rates will be determined from nuclear lifetimes measured using the Doppler-shift attenuation method following inelastic neutron scattering. Comparisons of our data with theoretical models will be made to obtain a better understanding of the low-lying collective excitations of these nuclei and their proton-neutron symmetry properties.
