Аннотация:We suggest a method for calculating scattering phase shifts and energies and
widths of resonances which utilizes only eigenenergies obtained in variational
calculations with oscillator basis and their dependence on oscillator basis
spacing ℏΩ . We make use of simple expressions for the S-matrix at
eigenstates of a finite (truncated) Hamiltonian matrix in the oscillator basis
obtained in the HORSE (J-matrix) formalism of quantum scattering theory. The
validity of the suggested approach is verified in calculations with model
Woods-Saxon potentials and applied to calculations of nα resonances and
non-resonant scattering using the no-core shell model.