Microscopic calculations for the 4He continuum. I

A new model for the 4He nucleus in which structure and reaction aspects are treated on an equal footing is introduced. The model is constructed within the framework of the dynamical R-matrix methodology. The internal states are expanded on a basis of properly symmetrized translationally invariant harmonic oscillator eigenstates including all states up to 4hω/2π of oscillator excitation. All three two-body break-up channels, namely d+d, t+p, and 3He+n are explicitly included. The two-body interaction is based on the Sussex matrix elements. In this paper, the formulation of the model is described, including the choice of two-body interaction, and results are given for the spectrum of resonances obtained within the model and for d+d elastic scattering and the 2H(d, p)3H reaction near threshold. The initial results are very encouraging, but also suggest that some further adjustments to the model are necessary. (Auth.)