Spin-One Particle in an External Electromagnetic Field

Equations of motion for a spin-one particle and its antiparticle in an external electromagnetic field are developed using a (1,0) {} (0,1) six-component wave function. Anomalous magnetic dipole and electric quadrupole effects are included. The wave equation is manifestly covariant and has no auxiliary conditions. The invariant integral for the system is derived, and the nonrelativistic limit is discussed. The semiclassical approximation for a relativistic spin-one particle in an electrostatic field is set up; then the problem of calculating the change of polarization reduces to a set of three coupled total differential equations.