Improved convergence of scattering calculations in the oscillator representation

The Schrِdinger equation for two and tree-body problems is solved for scattering states in a hybrid representation where solutions are expanded in the eigenstates of the harmonic oscillator in the interaction region and on a finite difference grid in the near- and far-field. The two representations are coupled through a high-order asymptotic formula that takes into account the function values and the third derivative in the classical turning points. For various examples the convergence is analyzed for various physics problems that use an expansion in a large number of oscillator states. The results show significant improvement over the JM-ECS method [Y. Bidasyuk, W. Vanroose, J. Broeckhove, F. Arickx, V. Vasilevsky, Hybrid method (JM-ECS) combining the J-matrix and exterior complex scaling methods for scattering calculations, Phys. Rev. C 82 (6) (2010) 064603].