SPIN PRECESSION OF ULTRARELATIVISTIC ELECTRONS IN A CIRCULARLY-POLARIZED ELECTROMAGNETIC-WAVE

A drastic growth in the frequency of the spin precession of ultrarelat ivistic electrons (positrons) in the field of a counterpropagating cir cularly polarized electromagnetic wave is predicted and its connection with the known effect of the rotation of gamma-quantum polarization i n a polarized electron target is demonstrated. It is shown that the ef fect considered corresponds to a correction of order alpha = 1/137 to the amplitude of the coherent forward Compton scattering and cannot be described by the Bargmann-Michel-Telegdi equation which corresponds t o a correction of order alpha(2) to this amplitude and predicts a thre e order of magnitude smaller precession frequency value as well as bot h its wrong sign and dependence on the electron energy and wave freque ncy. The discussed growth of the electron spin precession makes it rea lly possible to observe this phenomenon using available high energy el ectron beams and superintense subpicosecond lasers.