Time-dependent local-density theory of dielectric effects in small molecules

A time-dependent local-density theory of the photoemission spectra and polarizabilities of finite systems is extended from atoms to molecules. The theory is implemented in a single-center formulation and is applied to ${\mathrm{N}}_2$ and ${\mathrm{C}}_2$ ${\mathrm{H}}_2$. The partial photoemission cross sections and asymmetry parameters for the $1{\pi }_g$ and $3{\sigma }_g$ levels are presented as well as the optical-frequency polarizabilities; agreement with experiment is generally, but not uniformly, excellent.