Isospin mixing in light nuclei

Isospin mixing in light nuclei has been directly studied through isospin-forbidden resonances corresponding to high-lying T = 3/2 states in A = 4n + 1 T/sub z/ = -1/2 nuclei. High-lying T = 3/2 states in A = 25, 29, 33, and 37, and T/sub z/ = absolute value 1/2 nuclei were identified by the isospin-allowed (p,t) and (p,3He) reactions at a single angle with an incident proton energy of 42.4 MeV. Comparisons of angular distributions measured at 60 MeV for 27Al(p,t)25Al, 27Al(p,3He)25Mg, 31P(p vector,t)29P, and 31P(p vector,3He)29Si were used to assign T = 3/2 levels in the A = 25 and A = 29, T/sub z/ = absolute value 1/2 nuclei. A measurement system utilizing a high-resolution polarized proton beam was developed at Triangle Universities Nuclear Laboratory to measure (p vector,p) scattering over isospin-forbidden resonances. The polarized-beam energy excitation functions were analyzed to extract all resonance parameters from the results of a single experiment. A system was developed to measure directly the beam energy spread. Parameters for several previously studied first T = 3/2 resonances in the A = 4n + 1, T/sub z/ = -1/2 nuclei were remeasured to confirm the validity of our new measurement and analysis techniques. High-lying T = 3/2 isospin-forbidden resonances in 17F, 25Al, 29P, 33Cl, and 37K were studied and proton elastic-scattering reduced widths were extracted by a model-independent helicity amplitude analysis. The results of the present study indicate that the isospin mixing in a given nucleus does not increase monotonically with increasing excitation energy. The present study, in conjunction with previous work, indicates that the isospin mixing exhibits a smooth dependence with mass number A and is largely independent of nuclear structure