Trends in valence autoionizing Rydbergs for nd5 semifilled-shell ground and excited atoms and ions: Cr, Mn, Mn+, Fe+, Fe2+, Mo, Tc, Tc+ and Re

New regularities are reported for valence-shell autoionizing nd → n'p Rydbergs decaying to a continuous spectrum of the (n + 1)sq valence subshell of free metal atoms and ions with nd5 semifilled subshells: Cr(3d5 4s17S), Mn(3d5 4s2 26S), Mn+(3d5 4s17S), Fe+ (3d5 4s26 S), Fe2+(3d5)4s17S), Mo(4d5 5s17S), Tc(4d5 5s26 S), Tc+(4d5 5s17 S) and Re(5d5 6s26S). We predict an extreme narrowing for the nd → n'p autoionizing Rydbergs in the nd5 atoms and ions with a ground-state nd5(n + 1) sq=17S valence-shell configuration. In contrast, incomparably broader Rydbergs occur in both atoms and ions with a ground configuration nd5 (n + 1)sq=26S, or in metastable atoms and ions whose electron configuration is nd5 (n + 1)sq=15S. We also predict a drastic difference between the nd → n'p Rydberg profiles in partial (n + 1)s↑ and (n + 1)s↓ photoionization cross sections of the nd5 atoms and ions with a closed (n + 1)s2 valence subshell (arrows ↑ and ↓ show the two possible spin orientations for the ejected photoelectrons). The regularities disappear for atoms and ions with other than an nd5 semifilled subshell. The research is performed within both the 'spin-polarized' Hartree-Fock approach and the 'spin-polarized' random-phase approximation with exchange. (author)