ORBITAL MOTION IN DEFORMED-NUCLEI

A typical example of orbital motion is represented by the so-called sc issors mode [1]. This is induced by a rotational oscillation between p rotons and neutrons forming two deformed fluids and gives rise to M1 e xcitations mainly of orbital nature. These transitions were discovered for the first time in (e,e') experiments [2] and since then detected in most deformed nuclei.(1)) A long series of experimental and theoret ical investigations devoted to the understanding of the actual nature of these excitations have followed the first discovery. Specially impo rtant was the observation that the integrated M1 strength grows quadra tically with the nuclear deformation [4]. This law, which was explaine d theoretically in phenomenological as well as microscopic approaches( 2)) will be derived here by simply using an energy weighted sum rule a pproach, embedded in RPA [6]. The same sum rule is then computed and c ompared with the available experimental data.