Electron loss from heavy heliumlike projectiles in ultrarelativistic collisions with many-electron atomic targets

We study single- and double-electron loss from heavy heliumlike projectiles in ultrarelativistic collisions with neutral many- electron target atoms. The simultaneous interaction of the target with two projectile electrons is found to be the dominant process in the double-electron loss provided the atomic number of the projectile, Z(p), that of the target, Z(t), and the collision velocity, v, satisfy the condition Z(p)Z(t)/v>0.4. It is shown that for a wide range of projectile and target atomic numbers the asymptotic double-to-single loss ratio strongly depends on the target atomic number but is nearly independent of the nuclear charge of the projectile. It is also demonstrated that many-photon exchange between the target and each of the projectile electrons considerably influences the double loss in collisions with very heavy targets