ACCURATE MULTICHANNEL CONTINUUM STATES BY A GENERAL CONFIGURATION-INTERACTION EXPANSION IN A B-SPLINE BASIS - APPLICATION TO HE PHOTOIONIZATION

We report theoretical calculations of the total and partial cross sect ion and asymmetry parameter for He photoionization up to the N = 3 thr eshold. Multichannel continuum wavefunctions are obtained via a least squares solution of the Schrodinger equation employing a basis set exp ansion based on a primitive B-spline radial basis and a general config uration interaction form. This allows use of a mixed full CI and close -coupling expansion in a completely general approach to improve correl ation description in the continuum channels. The present algorithm cor rectly describes the full range of phenomena encountered with full det ails and a remarkable accuracy both on non-resonant cross sections and resonance structures. An accuracy of better than 0.001 Mb is estimate d both on total and partial cross sections, also Fano resonance parame ters compare very well with the best methods available based on Hyller aas type wavefunctions and complex coordinate rotation.