Triple-dipole interaction. I. theory

Abstract

Third-order perturbation theory is applied to the van der waals-type interaction between neutral atoms. An interaction between triplets of atoms results. The derivation of the third-order energy interaction W 0‴, is outlined, the procedure being somewhat similar to that used by London in his application of second-order perturbation theory to interatomic interaction. Since the perturbing potential is limited to the dipole-dipole term, the energy W0‴ is called the triple-dipole interaction. The latter depends not only on the interatomic distances but also on the shape of the triangle formed by the three atoms; W0‴ is positive for all acute and negative for most obtuse triangles.