LASER-MODIFIED LONG-RANGE FORCES BETWEEN NEUTRAL ATOMS

Modification of the long-range forces between atoms by laser light has been considered by Thirunamachandran (1980). More recently, Grossel a nd van Labeke (1994) treated the modified interaction between a conduc ting surface and an atom. In the present paper we establish the formul as for laser-modified Casimir forces between neutral atoms using a sem iclassical formalism. These forces appear as a result of interaction o f atomic dipoles with the background vacuum, in which spectral density is modified by the laser field. In particular, the interaction potent ial between two neutral atoms displays non-monotonic behaviour in an e xternal field for certain polarisations. The averaging of this result over the mutual position of the atoms coincides with Thirunamachandran 's result for the laser-modified Casimir forces. We give estimates for the Value of this interaction, which may dominate the Casimir force f or distances comparable to the wavelength. The validity of the semi-cl assical method is proven by comparison with the results of second-orde r perturbation theory. Furthermore, the method is used to calculate th e external field modification of dispersive forces between a magnetica lly polarisable body and an electrically polarisable one and a chiral system coupled to both electric and magnetic fields.