Relativistic Heavy-Ion-Atom Collisions

Abstract

This chapter reviews the atomic collisions of very heavy ions at relativistic velocities. The use of relativistic heavy ions permits several experimental simplifications. For example, the main source of error in x-ray-producing cross-section measurements at low velocities is the beam intensity normalization, determined either by beam current integration or Rutherford scattering normalization. With relativistic heavy ions, the cross sections are often very large thus making it possible to count every incident ion with ≈100% efficiency using surface barrier or scintillator detectors. An active collimation system can be used to measure x-ray cross sections using relativistic heavy ions, which can pass through several grams/cm of matter. Furthermore, relativistic, very high-Z atoms present special opportunities for atomic structure experiments because any atom in the periodic table can be stripped to few-electron or even bare ions. Relativistic and quantum-electrodynamics (QED) effects can then be examined in systems where they are very large, can be experimentally isolated, and where precise and unambiguous calculations can be performed. The understanding of relativistic ions allows, for the first time, the formulation of an ab initio theory of ions in matter incorporating excited-state effects.