Theoretical study of PbO and the PbO anion

PbO and PbO− were studied utilizing CCSD(T), CASSCF/CASPT2, and the Fock Space FSCCSD methods. Relativistic effects were treated by the spin-free, two-component infinite-order Douglas–Kroll–Hess, Dirac–Coulomb and the restricted active space state interaction RASSI–SO methods. Our adiabatic electron affinity (EA), 0.696 eV, agrees favorably with experiment (0.714 eV). Theoretical dissociation energies De of PbO and PbO− (3.91 and 3.20 eV) differ from experiment by 0.04 and 0.07 eV, respectively. The electron correlation, relativistic scalar and spin–orbit effects are crucial for obtaining good agreement of theoretical and experimental data for EA and De. Equilibrium bond distance and vibrational frequency are less sensitive to SO effects.