Analytical description of longitudinal optical binding of two spherical nanoparticles

We present a modified analytical model describing optical forces acting on two spherical nanoparticles arranged longitudinally in two counter-propagating beams. These particles interact with light as Rayleigh particles and are approximated by dipoles. We focus on the key phenomena of longitudinal binding between these two objects and therefore we applied the general analytical solution to two counter-propagating beams with zero intensity gradients along their propagation (Bessel beams). Numerical results coincide with a numerical model based on the coupled dipoles method.