Philip H. Jones, Onofrio M. Maragò & Giovanni Volpe
Fig. 3.1 — Electric dipole induced on an atom
In the presence of an electric field, E, positive and negative charge distributions within an atom (or molecule or nanoparticle) are displaced in opposite directions: the positively charged nucleus parallel to the electric field direction and the negatively charged electronic cloud antiparallel to it. The direction of E is indicated by the arrow near each atom.