2-PHOTON DECAY OF THE 1ST EXCITED 0+ STATE IN O-16

Recent experiments observed unexpectedly strong interference between the E1-E1 and M1-M1 2 decay modes of the 0+ (6.05 MeV) state in O16. We present the results of a detailed calculation which evaluates the two-photon amplitude between realistic nonspurious many-body wave functions derived from a large basis SU(3) shell-model calculation, including up to 5Latin small letter h with stroke of excitation. It is found that, as a result of strong cancellation between contributions to the transition polarizability from the giant dipole states built on the closed shell and the deformed (6.05 MeV) 0+ state, the 2E1 matrix element is greatly suppressed. Since the standard one-body M1 operator cannot excite the closed shell, strong cancellations are not seen in this case. The resulting 2M1 decay mode becomes competitive with the 2E1 decay, although it is still underestimated by the calculations. © 1990 The American Physical Society.