  We investigate the possibility to control the s-wave scattering length for
the interaction between cold bosonic atoms by using a microwave field. Our
scheme applies to any atomic species with a ground state that is split by
hyperfine interaction. We discuss more specifically the case of alkali-metal
atoms and calculate the change in the scattering length for 7Li, 23Na, 41K,
87Rb, and 133Cs. Our results yield optimistic prospects for experiments with
the four latter species.
