Further aspects of enhanced ion scattering near 180 degrees.
The role of rainbow scattering in enhanced ion scattering near 180{degree} was explored by comparing calculated enhancements for protons and antiprotons. Since the rainbow effect does not occur for negative particles and since the enhancement was much smaller for them than for positive particles, this comparison demonstrated in a more direct way than previously done the importance of rainbow scattering in producing the enhancement. A procedure for calculating a similarity factor between the ingoing and outgoing portions of a trajectory was developed, and its use showed that trajectories returning near 180{degree} differ in nature from random-return trajectories. A discussion is given of the possible relationship of the enhancement to phenomena such as the correlation effect in self-diffusion by the vacancy mechanism in solids and surface-structure studies by impact-collision ion-scattering spectrometry.
The two-atom model in enhanced ion backscattering near 180° scattering angles☆
Abstract The recent discovery by Pronko et al. of an unusual enhancement of the yield of ions backscattered through angles close to 180° from the near surface regions of solids is investigated using a two-atom scattering model. The model predicts an enhancement effect in amorphous solids whose physical origin arises from the tolerance of path for those ions whose inward and outward trajectories lie in the vicinity of the critical impact parameter. Predictions are given of the dependence of the yield enhancement on the following parameters: ion energy, backscattering depth, exit angle, scattering potential, atomic numbers of projectile and target, and atomic density of target.
Effect of Channeling on Damage Rates Associated with Heavy-Ion Irradiation of Gold
Electron microscope studies of radiation damage produced by 60-MeV iodine ions in thin gold crystals have been made to determine the dependence of damage rate on orientation of the ion beam relative to [011] and (111). Experimental values of the minimum damage rates and half-widths were compared with calculations made with a Monte Carlo computer program using either the Thomas-Fermi or the Bohr potential and incorporating thermal vibrations. The thermal vibrations were found to be necessary for agreement with experiment, and agreement was better with the Thomas-Fermi potential than with the Bohr. Experimental observations by a stereo technique gave a tentative confirmation of a calculated depth dependence and showed in addition a deficiency of damage clusters near the surface. 
 
 
 
Strahlenschaden, durch 60 MeV-Jodionen in dunnen Goldkristallen erzeugt, wurden mit dem Elektronenmikroskop untersucht, um die Abhangigkeit der Schadigungsrate von der Orientierung des Ionenstrahles relativ zu [011] und (111) zu bestimmen. Experimentelle Werte der minimalen Schadigungsrate und Halbwertsbreite wurden mit Monte-Carlo-Rechnungen verglichen, die ein Thomas-Fermi-und ein Bohr-Potential benutzten und thermische Schwingungen berucksichtigten. Die Hinzunahme von thermischen Schwingungen war notig, um Ubereinstimmung mit dem Experiment zu erzielen. Das Thomas-Fermi-Potential ergab bessere Ergebnisse als das von Bohr. Beobachtungen mit einer Stereotechnik ergaben eine vorlaufige Bestatigung der berechneten Tiefenabhangigkeit und zeigten zusatzlich eine Verminderung von Strahlenschadenclustern nahe der Oberflache.