Abstract
The ground and excited states of the H-3 and He-4 nuclei are studied in the framework of group-theoretical methods. Basis functions of the unitary scheme model corresponding to even numbers of quanta of excitation in the range 0 <= N <= 20 are constructed for the even-parity states of these two nuclei, and bases with 1 <= N <= 19 are constructed for the odd-parity states of the He-4 nucleus. The ground-state and first-excited-state energies and wave functions, the ground S-, P- and D-state probabilities, the root-mean-square radius and the magnetic dipole moment of triton are calculated. Furthermore, for the He-4 nucleus, the spectrum and the wave functions, the ground S-, P- and D-state probabilities, the root-mean-square radius and the total integral cross section of the dipole electric transition accompanying the photoabsorption of gamma quanta by this nucleus are calculated. The GPT and AV8' two-body interactions and the UIX three-nucleon interaction are used in these investigations. Moreover, the convergence of the calculations is examined by incrementally extrapolating the nuclear characteristics calculated for N <= 20 to N = 30 for both nuclei.