  The spectroscopic studies have identified few Actinide and Lanthanide nuclei
of the periodic table, which can assume the pear shape. The low frequency
collective rotation of these nuclei has been established by determining the
band structure of the excited levels and their gamma decay rates. In this
article, we report the rotation of a pear-shaped nucleus in 100 Ru, which
rotates nearly three times faster than the previously known cases. The three
novel consequences of this fast rotation are: the realization of a pear-shape
in an excited state, its moment of inertia becoming a constant of motion and
its shape evolution. These inferences have been arrived at by comparing the
characteristics of the rotational band of 100 Ru with three of the best-known
examples of a rotating pear-shaped nucleus and through the theoretical
interpretation of the data. The observation of a pear-shaped nucleus in the
lighter mass region opens up the possibility of a systematic study of the
effects of fast rotation on this shape.
