Coupling of NMR absorption to the motion of nonaxisymmetric vortices in rotating ³He-B

The phase-shifted NMR absorption response of an array of vortices to a harmonic modulation of the rotation velocity is discussed. The measured phase lag between the rotation drive and its response can be explained by a torque, which acts on the nonaxisymmetric vortex core cross-section and derives contributions from both the vortex displacement and velocity. The result supports the earlier conclusion that the NMR absorption signal can be employed for studying vortex motion in rotating ³He-B.