Contributions of R.H. Ritchie to the understanding of charged particle penetration phenomena

Contributions of R.H. Ritchie to the understanding of phenomena associated with the penetration of charged particles in condensed matter are reviewed. Ritchie was the first to predict the existence of the surface plasmon and to suggest how it might be observed experimentally, and has since made many contributions related to it. He pioneered in developing theoretical concepts and methods in numerous other areas including energy loss of charged particles. transport theory, nonlinear response of solids, the charged-particle wake, stopping power for slow ions, self-energy of slow electrons, and theoretical electron microscopy. Other trailblazing work of his, including various aspects of radiation dosimetry, and instrument theory and design, are discussed briefly