In addition, different elements can be distinguished because the scattered energies are determined by the masses of the target atoms.

The result is an excluded volume behind the target atom into which no ions penetrate.

This target atom then itself becomes a projectile in the solid, and can cause successive collision events.

Many recent experiments have used einsteinium as the target atom.

The projectiles may be backscattered (at an angle of up to 180 ) upon collision with a target atom.

Hence the depth that each target atom was hit can also be determined.

Then what happens is the target atom finds itself with an unoccupied "hole" in the electron structure.

This has been found to be a function of the atomic number of the target atom and photon energy.

All of these processes have cross sections which depend on the impact parameters involved in collisions with individual target atoms.

However, one of the simplest to grasp conceptionally is that the mass on the target atom is known.