Magnetic octupole scattering of neutrons

The authors estimate the cross section for the magnetic octupole scattering of neutrons by rare-earth ions. These scattering events can change the magnetic quantum number of the ions by up to three units. For high momentum transfers and a proper scattering geometry, the cross sections for magnetic octupole mod Delta M mod =2 and 3 transitions are comparable with those for magnetic dipole mod Delta M mod =1 transitions. If a beam of polarized neutrons is used, mod Delta M mod =2 excitations, i.e. quadrupolar waves, can be produced without exciting spin waves mod Delta M mod =1. Examples are quoted where this scattering is expected to be of particular interest.