STRUCTURES AND PROPERTIES OF DOUBLE-RYDBERG ANIONS

Double-Rydberg anions consist of a closed-shell cation core and two Rydberg-like, diffuse electrons. Ground-state geometry optimizations disclose stable minima for OH3-, NH4-, and PH4- but not for SH3-, FH2-, and ClH2-. An alternative PH4- structure with C2v symmetry, based on valence shell electron pair repulsion theory, is a more stable minimum than its double-Rydberg counterpart. Vibrational frequencies of the minima are reported. Other optimizations of alternative structures based on valence shell electron pair repulsion theory converge either to double-Rydberg minima or to transition states. Electron propagator calculations yield ionization energies for the minima. © 1990 American Chemical Society.