Cooper-Type Minima in Multipole Cross Sections of Atomic Hydrogen

The quadrupole photoionization cross sections for hydrogen are shown to contain minima at kinetic energies of the free electron that are less than 2 eV. These minima are the result of zeros that occur in some of the quadrupole transition strengths between bound excited ($|n,l〉$) and continuum ($|W,l+2\mathrm{}〉$) states for atomic hydrogen. These minima are compared with Cooper minima which occur in the photoionization cross sections for some multielectron systems.