Hyperspherical L2-integrable basis method for energetic proton and anti-proton impact autoionization

A hyperspherical L-2-integrable basis set is presented for use in expanding the semiclassical time-dependent close-coupling equations. We discuss advantages of the method in the light of other conventional L-2-integrable basis expansion methods and the previously implemented hyperspherical energy-discretization method. By means of the present basis set, electron emission cross sections of autoionizing states of helium due to energetic proton and anti-proton impact are evaluated for demonstration. We find contrasting behaviours of the electron emission cross sections in the He** (N = 3) manifold due to proton impact and to anti-proton impact caused by the interference between the two final continuum states of He(1s) + e and He(2s) + e. An argument based on the sudden approximation accounts for the disappearance of the difference in the total electron emission cross sections.