A comparison between projectile electron loss cross sections for negative, F-, and positive, He+, projectiles is presented for collisions with Ar target. The behavior of the two collision systems is similar for the projectile electron loss with target ionization. For projectile electron loss without target ionization (the so-called screening electron-loss process), quite different situations are presented for the studied positive and negative projectiles. For He++ Ar, the loss without target ionization collision channel is negligible for intermediate-to-low energies. On the other hand, for F-+ Ar, this collision channel is the dominant one in the total projectile electron loss at intermediate-to-low velocities. The roles played by coupling with the electron capture by the projectile collision channel and by the very different binding energies for negative and positive projectiles are discussed.
Anion; Negative ions; Collision; Projectile electron loss
