Abstract

In the non retarded regime, atom-surface van der Waals (vW) interactions originate in the forces between the fluctuating atomic dipole and its instantaneous image linked to polarisation charges induced in the surface. vW interactions which are generally attractive (distance law in 1/z3) are of fundamental importance in many fields of physics, chemistry and biology. The existence of vW repulsion has recently been demonstrated when there is a resonant coupling between the fluctuating atom dipole and a surface resonance [1]. Because of cylindrical symmetry around the normal $\left(0\overrightarrow{z}\right)$ to a plane surface, the surface near field is anisotropic and vW interactions exhibit a quadrupolar component, proportional to $D_z^2-{\overrightarrow{D}}^2/3(\overrightarrow{D}$, atomic dipole operator). This off-diagonal coupling may be responsible for a symmetry breaking of the atomic wave functions, allowing for the appearance of free-space forbidden transitions.

© 2000 IEEE