Sommerfeld Particle in Static Magnetic Field: Tunneling and Delayed   Untwisting in Cyclotron
  Motion of a charged particle with finite size, described by Sommerfeld model, in static magnetic field has two peculiar features: 1.) there is the effect of tunneling - Sommerfeld particle overcomes the barrier and finds itself in the forbidden, from classical point of view, area; 2.) the untwisting of trajectory in cyclotron for Sommerfeld particle is strongly delayed compared to that of a classical particle. 
Alexander A.Vlasov