Systematics of zeros in dipole matrix elements for photoionizing transitions: Nonrelativistic calculations

The location of the zeros in dipole matrix elements for photoionizing transitions (Cooper minima) in ground states of atoms has been calculated for all subshells over the entire periodic system. These zeros occur for all subshells whose wave functions have nodes, except the 2s subshell. The behavior of these zeros, as a function of the atomic number Z, has been examined and their ``trajectories'' are rather complicated. The trajectories are explained primarily in terms of initial-state quantum defects and final-state phase shifts. All atoms with Z>10 have at least one zero, and some have as many as five zeros.