  We demonstrate that the acoustic spin of a first-order Bessel beam can be
transferred to a subwavelength (prolate) spheroidal particle at the beam axis
in a viscous fluid. The induced radiation torque is proportional to the
acoustic spin, which scales with the beam energy density. The analysis of the
particle rotational dynamics in a Stokes' flow regime reveals that its angular
velocity varies linearly with the acoustic spin. Asymptotic expressions of the
radiation torque and angular velocity are obtained for a quasispherical and
infinitely thin particle. Excellent agreement is found between the theoretical
results of radiation torque and finite element simulations. The induced
particle spin is predicted and analyzed using the typical parameter values of
the acoustical vortex tweezer and levitation devices. We discuss how the beam
energy density and fluid viscosity can be assessed by measuring the induced
spin of the particle.
