  An absorptive Rayleigh dielectric sphere in a non-diffracting non-paraxial
fractional Bessel vortex beam experiences a spin torque. The axial and
transverse radiation spin torque components are evaluated in the dipole
approximation using the radiative correction of the electric field. Particular
emphasis is given on the polarization as well as changing the topological
charge and the beam's half-cone angle. When the beam order is zero, the axial
spin torque component vanishes. However, when the beam order becomes a real
positive number, the vortex beam induces left-handed (negative) axial spin
torque as the sphere shifts off-axially from the center of the beam. The
results show that a non-diffracting non-paraxial fractional Bessel vortex beam
is capable to induce a spin reversal of an absorptive Rayleigh sphere placed
arbitrarily in its path. Potential applications are yet to be explored in
particle manipulation, rotation in optical tweezers, optical tractor beams, the
design of optically-engineered metamaterials to name a few areas.
