Electron-impact ionization of atomic hydrogen

Exterior complex scaling enables one to solve the time-independent Schrödinger equation for three charged particles without explicitly imposing the asymptotic boundary condition for three-body breakup. We have used this formalism to study electron-impact ionization of atomic hydrogen by directly solving for the radial components of the scattered wave on a complex, exterior scaled numerical grid. Computational procedures, presented briefly elsewhere [T. N. Rescigno, M. Baertschy, W. A. Isaacs, and C. W. McCurdy, Science 286, 2474 (1999)], are discussed here in greater detail and additional results are presented. Our method is limited only by the finite size of the grid and the number of partial-wave components retained in the expansion of the wave function and, unlike other methods that have been used to study ionization, involves no uncontrolled approximations. Our calculated triply differential cross sections at 17.6, 20, 25, and 30 eV are found to be in excellent agreement with recent measurements.