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.
Kitchen Conversations: Democracy in Action at the Lower East Side Tenement Museum
Abstract This article describes the Lower East Side Tenement Museum9s ongoing public dialogue on immigration, the first in the United States. As she joins facilitators in reflecting on the importance of dialogue in a democracy, museum president Ruth J. Abram explains how and why the program was initiated, the obstacles that had to be overcome, and the public reaction to it. Kitchen Conversations represents the museum9s commitment to the proposition that historic sites must function as places of civic engagement, using the history they interpret as a starting place for dialogue on related contemporary issues.