A new method describing nuclear rotational motion microscopically is
proposed. We extract the rotational Hamiltonian by introducing the intrinsic
pair modes which commute with the rotational mode. Thereby the rotational mode
is not treated as zero energy mode in contrast with the conventional RPA
formalism so that we circumvent the difficulty related with infrared
divergence. The wave function is constructed by angular momentum projection on
each intrinsic state. Without numerical integration for projection we calculate
the matrix elements analytically under a certain approximation. The numerical
calculations are carried out to illustrate the applicability of our method and
they show that our method works well.Comment: 14pages,1figur