It is shown that the quantitative description within the two-rotor model of the low-lying, moderately collective M1 excitation observed in deformed nuclei and known as the scissors mode can be drastically improved by properly computing the relevant physical quantities that determine the properties of such a mode. A two-fluid formulation of the model in which only the nuclear mass external to a rotational invariant inner core of each rotor takes part in the motion is also presented and discussed, especially in relation to the algebraic interacting boson model and to the random phase approximation. The importance of dynamical correlations is stressed in this connection.

• Received 18 May 1989

DOI:https://doi.org/10.1103/PhysRevC.42.241