Ponderomotive forces acting upon relativistic electrons in an inhomogeneous light field

Ponderomotive forces acting upon relativistic electrons in an inhomogeneous light field are found. In contrast with the nonrelativistic case, relativistic ponderomotive forces are shown to consist of several components, only one of which is directed along the gradient of intensity. Two other components are directed along the light polarization vector and along the focal axis of a focused light beam. The conditions are found under which these additional components of relativistic ponderomotive forces are significantly larger than the gradient component.