Dipole strength distribution in doubly even deformed nuclei

The M1 and E1 strength distributions in the energy range 3-12 MeV are calculated in random-phase approximation for the deformed nuclei 154Sm, 168Er, 178Hf and 238U. It is found that the orbital motion, although providing on the whole a modest contribution to the M1 strength, plays a significant role in shaping the M1 spectra because of the destructive interference between orbital and spin amplitudes. Strong E1 transitions also occur in the same energy range. Their total strength in the energy range 3.6-7.6 MeV is about four times larger than the M1 strength. Because of these highly intense E1 transitions, the total dipole strength distribution computed as a sum of the M1 and E1 strengths is considerably different from the spectra of the M1 transitions alone.