Unitary scheme model calculations of the ground and excited state characteristics of ³H and ⁴He

The ground and excited states of the ³H and ⁴He 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 ⁴He 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 ⁴He 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 γ 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. (paper)