On the application of Lorentz and Coulomb gauges for calculations of ionization of light targets by relativistic charged projectiles

We consider the application of the Lorentz and Coulomb gauges to treat collisions of relativistic charged projectiles with light atomic targets. We use the approach where the nonrelativistic description of the target is combined with the relativistic treatment of the projectile field. It is shown that the Coulomb gauge has a great advantage as compared with the Lorentz one if exact eigenstates of the target nonrelativistic Hamiltonian are not available. The reasons for this are discussed.