A new description of nuclear rotational motion in terms of the intrinsic pair mode

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