title: Comment on "Trapping force, force constant, and potential depths for dielectric spheres in the presence of spherical aberrations".
abstract: I point out a confusion that is rather common in optical forces, i.e., that the time average of the Lorentz force on a dipole (for a harmonic time-varying field) is sometimes assumed to be a gradient force that is due to omission of the radiative reaction term in the polarizability of the dipole.
authors.affiliation: Institut Fresnel, Unité Mixte de Recherche 6133, Faculté des Sciences et Techniques de St Jérôme, Avenue Escadrille, Normandie-Niemen, F-13397 Marseille Cedex 20, France. patrick.chaumet@fresnel.fr
authors.forename: Patrick C
authors.initials: PC
authors.lastname: Chaumet