The present paper shows that the nature of the polarization of charged spin-1/2 particles moving in a uniform magnetic field changes dramatically in a relatively weak transverse axisymmetric magnetic field. The direction along which the spin projection is quantized has a fixed orientation with respect to the axes of a cylindrical coordinate system and can form a substantial angle with the direction of the uniform magnetic field. The presence of spin quantization is proved both by the fact that the commutator of the Hamiltonian operator and the projection of the polarization operator in the direction of quantization is zero and by analyzing the Bargmann-Michel-Telegdi equation for this given case. Finally, the possibilities of detecting this effect and utilizing it are discussed.
The question as to whether neutron acceleration can occur in uniform electromagnetic fields is examined. Although such an effect has been predicted using the canonical equations of motion, some doubt has been raised recently as to whether it is in principle observable for a spin-1/2 particle. To resolve this issue a gedanken experiment is proposed and analyzed using wave-packet construction for the neutron beam. By allowing an arbitrary orientation for the neutron spin as well as for the electric and magnetic fields, a nonvanishing acceleration of the center of the neutron wave packet is found that confirms the predictions of the canonical formalism.