On the enhancement of M1-transitions from neutron resonances in the Ba and Ce isotopes

The M1-strength functions for transitions from the ground states of ^136,138Ba and ¹⁴⁰Ce to the states lying near the neutron binding energy B_n are calculated within the quasiparticle-phonon nuclear model. The calculated M1-strength functions describe well the relevant experimental data. It is shown that a notable enhancement of the M1-transitions is caused by the proximity of the maximum of the M1-resonance to B_n. As a result the intensities of the E1 and M1-transitions appear to be close to each other.