A theoretical study of the electron affinity of methylene

Ab initio multireference configuration interaction calculations yield an electron affinity of 0.604 ± 0.03 eV for methylene (3B 1), in excellent agreement with the best observed value of 0.628 ± 0.031 eV. The estimated theoretical error limit of 0.03 eV is based on energy convergence with respect to systematic expansion of both reference configuration space and one-particle basis set. Convergence to the full CI electron affinity is rapid, and significantly accelerated when corrections for quadruple electron excitations are included. © 1989 American Institute of Physics.