No abstract

We present a realistic calculation of the frictional coefficients for 2SSi+2~ system using the two-center shell model on the basis of the linear response theory. Adopting the center separation R and the deformation 6 as collective variables we study the dependence of frictional coefficients 7RR, )'R6 and y66 on those variables, for various values of the neck parameter e, the temperature T and the smearing width F. The direct application of the linear response theory to the two-center potential gives non-vanishing friction for the simple translational motion of the two fragments even when they are far apart. A method to avoid this energy dissipation is proposed and is used in the calculation. Results show that the form factor of the frictional force is surface-peaked and the peak becomes lower as the prolate deformation or neck formation increases. Temperature dependence is mild, but is not negligible. We compare our 7RR and ~',~ with other models.

The exciton model for the pre-equilibrium emission of light composite particles proposed and applied to the (p,n) reaction of Iwamoto-Harada is further investigated for the energy spectra of the (p,d), (p,t), and (p, 'He) reactions with incident energy of several tens of MeV's. Calculated results could reproduce an overall feature of those spectra. The dominance of the pickup-type contribution which occurs in the course of the equilibration process was found to be common for all composite particles. The degree of fitting to the data is excellent for (p, t) reactions to the same extent as for (p,a) reactions, and is somewhat less for the high energy part of energy spectra of (p, He) and (p,d) reactions. The relative ratio of yields of high energy composite particles was also reproduced fairly well with our model. These facts suggest that the simple reaction mechanism assumed in our model accounts for characteristics of the pre-equilibrium emission of light composite particles.

No abstract

667The a-particle reduced widths r a 2 for the ground state in Po2lO and Po212 are calculated -on the basis of the nuclear shell model. The calculations are made taking the boundary condition in an approximate way into consideration. The effects of the configuration mixing of the parent and daughter nucleus wave functions on ra2 are examined and it is found that they give quite large contributions to ra 2 • Some features of the distortion of the two nucleon wave functions arising from the configuration mixing are discussed graphically. It is shown that the wave function of relative motion with the mixing of the level which is lowered from the upper band by spin-orbit force would correspond to the bound electron-pair in the superconducting metals. Although there are some una voidable uncertainties in the course of the calculations, it is concluded that the wave functions deri vecl by conventional shell model calculations can explain the major part of the experimental values of r a 2 • examine to what extent the experimental values of r a 3 are explained by the independent particle model within a finite well, such as harmonic oscillator shell model. In the case of light nuclei, we can expect large r a 2 also from the independent particle model,uJ since both protons and neutrons are in the same at NERL on

No abstract

Taking the relative distance R and the deformation iJ of each nucleus as the collective variables, we solve the two dimensional coupled dynamical equations of motion with friction in the framework of the linear response theory. In solving the equations of motion, we approximately replace the inertia tensor with the hydrodynamical one and use the modified liquid-drop one as the collective potentiaI energy. As the frictional coefficients we use the microscopically calculated ones in the previous paper. The calculation is done for the reaction of 2sSi+2~ in which the incident energy of Z~ is 120MeV. Results show that our microscopically calculated friction gives the large value of energy dissipation which amounts to the "completely damped" collision. Besides it, growths of the oblate deformation in the entrance channel and the prolate deformation in the exit channel are clearly seen. They give a large influence on the time development of the energy dissipation. We compare our calculated results with the experimental data for the reactions of 120 MeV 2~ with 27A1. The agreement between them is found to be reasonably good.

A microscopic calculation has been done for the friction coefficient for use in the deepinelastic collision of heavy nuclei. We adopted the formalism of the linear response theory as a basis and used the adiabatic base of the two-center shell model. Several reaction channels with the total mass numbers of 236 and 260 systems were investigated. The friction coefficients for the radial and deforming motions including the coupling term were calculated as a function of the distance between two nuclei and deformation of the two nuclei for each channel. The general feature of the friction coefficient, its strength and form factor, was clarified in this model and comparison with the results of other models were done. It was found that our model gives a physically plausible value for the friction coefficient as a whole.