Influence of Atomic Electrons on Radiation and Pair Production

A fast electron passing through matter will radiate at a greater rate than would be expected if the atoms traversed presented to the electron simply a static field of force. This follows because of the additional possibility of collisions in which an atom is excited. In a similar way energetic quanta will produce pairs at a greater rate. Consequently the unit of length characteristic of the multiplicative production of showers will be decreased...