The static polarizability behavior of the ground-state CO molecule is obtained by ab initio calculations. Single-configuration electronic wave functions are computed using a Hamiltonian which includes the interaction with an external electric field. At fields which approach ionization the polarizability increases markedly, by at least 30%, and cannot be adequately described by the usual multipole expansion.

• Received 31 May 1968

DOI:https://doi.org/10.1103/PhysRevLett.21.271