Depth distribution of damage due to ionization

The depth distribution of the damage due to ionization caused by heavy ion irradiation is calculated by the transport equation method previously used for the calculation of range and damage distributions. The calculation differs from Brice's chiefly in that it allows for the transport of energy by recoils away from the primary projectile path. Like the damage distribution, it should be more accurate than Brice's at low energies. It is found that a power-law limit of the ionization distribution can be constructed; thus one may take advantage of the simple scaling properties of power-law distributions. The importance of energy transport by recoils is examined for both ionization and damage distributions. A qualitative distinction between the ionization distribution and range or damage distributions is that the ionization distribution is discontinuous at the target surface. (This refers to the infinite target of the calculations, where the ''surface'' is merely a plane at which ion motion starts.) The differential-equation method of obtaining distributions from moments is generalized to allow inclusion of this discontinuity. (U.S.)