Electric-dipole transitions in deformed rare-earth nuclei

Both the absolute magnitude and the angular-momentum dependence of electric-dipole (E1) transition probabilities in quadrupole-deformed rare-earth nuclei are investigated in connection with the yrast spectroscopy. It is found that even in the most stable nuclei against octupole deformations the features of the measured E1-transition probabilities are not explained without invoking a coupling to octupole vibrations together with the E1 momentum carried by the octupole modes. The influence of octupole modes with both Kπ=0- and 1- on E1 transitions is discussed. (orig.)