Multiconfiguration resonating-group theory of the seven-nucleon system with realistic cluster wave functions

The properties of the seven-nucleon system are examined with a multiconfiguration and multi- channel resonating-group calculation. The cluster internal functions employed explain the charge-form-factor data over a wide range of $q^2$ and satisfy the variational stability condition quite well. The model space used is spanned by ${}_{}{}^3{}_{}{}^{}$H+α, n${+\mathrm{}}^6$Li, n${+\mathrm{}}^6$ ${\mathrm{Li}}^{\mathrm{*}}$, and d${+\mathrm{}}^5$He cluster configurations. The result shows that the specific distortion of the ${}_{}{}^3{}_{}{}^{}$H+α system is quite significant. With our multiconfiguration calculation, the ground-state energy is improved by more than 1 MeV. The calculated level spectrum agrees well with the level spectrum empirically determined. The energy positions of both natural-parity and unnatural-parity levels are reasonably explained. In addition, we find that, because of centrifugal-barrier effects, the aligned configuration generally makes the most sig- nificant contribution. The characteristics of nucleon-exchange terms are also briefly examined. Here it is found that, at sufficiently high energies where sharp resonance levels do not exist, the essential properties of these terms can already be learned by performing relatively simple single-configuration calculations.