Hyperspherical approach to the calculation of few-body atomic resonances

Direct solution of the Schrödinger equation for the doubly excited resonant [Formula Presented] state of the helium atom is obtained with the help of the complex rotation method (which reduces the resonance problem to that of bound states with complex energy) and the correlation function hyperspherical harmonic (CFHH) method. In the CFHH method the solution is a product of a correlation function and a smooth factor expanded into hyperspherical harmonic functions. Given a proper correlation function, chosen from physical considerations, the method generates resonant wave functions, accurate in the whole range of interparticle distances. Since the method is nonvariational no stabilization procedure is needed. The calculated energy and width are shown to be strictly independent of the angle of complex rotation, hence there is no need for the angle optimization procedure as well. The results are compared with variational and other precise computations.