Bethe formula

As of the most recent edition, this seems to have disappeared with the formula being called only the "Bethe formula".

At low energy, the energy loss according to the Bethe formula therefore decreases approximately as v with increasing energy.

Hence, this difference is called Barkas effect or Barkas-Andersen effect, see Bethe formula.

The Bethe formula is sometimes called "Bethe-Bloch formula", but this is misleading (see below).

The Bethe formula is only valid for energies high enough so that the charged atomic particle (the ion) does not carry any atomic electrons with it.

In 1930, he devised a formula for the energy loss of swift charged particles in matter called the Bethe formula, which is as important now as it was then.

It can be theoretically determined to an accuracy of a few % in the energy range above several hundred keV per nucleon from theoretical treatments, the best known being the Bethe formula.

The Bethe formula describes the energy loss per distance travelled of swift charged particles (protons, alpha particles, atomic ions, but not electrons) traversing matter (or alternatively the stopping power of the material).

Since the atomic number (Z) of alpha particles is exactly twice as big as that of protons, that means that the stopping power is not exactly proportional to Z, as the simple Bethe formula would have it.

By this time, it was known that the main process by which mesotrons lose energy is ionization energy loss, which is described by the Bethe formula and is essentially proportional to the mass per unit area of the layer of material traversed.