SHEARS MECHANISM AND PARTICLE-VIBRATION COUPLING

The shears mechanism, underlying the rotational-like behavior observed in the M1 bands in neutron deficient Pb isotopes, is interpreted as a consequence of a residual interaction between the proton and neutron blades. By deriving the angle 0 between the proton and neutron spin ve ctors (J) over right arrow(pi) and (J) over right arrow(pi) in the Pb- 198,Pb-199: bands, it is shown that the main ingredient of this effect ive force can be described by a P-2(0) term with a strength of 400-600 keV. Such an interaction can be mediated through the core by particle -vibration coupling, and qualitative agreement with experimental estim ates may indicate the possible role of this coupling in the appearance of shears bands.