The Exact Angular Momentum Projection Of The Nilsson Mean-Field Plus Nearest-orbit Pairing Model And Its Application To^18,19O

In this thesis,the exact angular momentum projection and the approximate angular mo-mentum projection,in which only intrinsic states with K = 0 are taken into account,for the Nilsson mean-field plus the nearest-orbit pairing model are proposed and analyzed.In the two projection schemes,the key step is to calculate the inner products of the intrinsic states of the model and the intrinsic states with a definite angular momentum,with which we can expand eigenstates of the model after the projection in terms of product of the single-particle states in the spherical shell model.In order to study whether the projected deformed shell model plus the pairing interaction can describe properties of deformed nuclei,the exact angular momentum projection and approximate angular momentum projection schemes are used to study low-lying spectra and electromagnetic properties of even-even 18O.The fitting results show that the struc-ture of the energy levels obtained after the approximate projection is the same as those of the exact projection.Moreover,the theoretical results of low-lying levels and electromagnetic prop?erties agree to the corresponding experimental results,which elucidates the reasonability and feasibility of the approximate projection scheme.Due to the fact that the dimension of the intrinsic subspace is greatly reduced when the approximate angular momentum projection is adopted,the superiority of the approximate angular momentum projection scheme will become more significant when it is applied to study nuclei with more number of valence particles.As a simple example of the first application of the projection of the model to odd-A nuclei,the exact projection scheme is used to study 190.Low-lying spectra and electromagnetic properties are calculated and compared to the corresponding experimental values.The fitting results show that properties of this odd-A nucleus can indeed be described by the deformed Nilsson model plus the pairing interaction well after the exact angular momentum projection.