Few-Body Dynamics in Simple Atomic Systems

Missouri University Of Science And Technology, Rolla MO

Investigators

Abstract

Understanding how objects large and small move and interact with each other is essential in our knowledge of nature and in developing technologies. The interactions of even a small number of objects can be challenging to understand. The "few body problem" (FBP) of physics refers to scenarios where three or more objects mutually affect each other's trajectories. These scenarios arise in the gravitational interactions of planets and stars and in the electromagnetic interactions of atoms, ions, and electrons. At the microscopic scale, the laws of quantum mechanics also affect particle motions. The resulting dynamics are challenging to predict, but can be important for understanding atomic collisions and basic reactions. This project will study atom-electron-ion scattering to test new theories about the FBP in atomic systems. In particular, when the particles in the FBP obey the laws of quantum mechanics, then the wave-particle duality is important. This project will investigate how the nonlocal spatial extent, or coherence length, of the quantum mechanical waves that represent the particles can affect the way particles scatter from one another. This will lead to improved understanding of reaction cross sections and scattering theory. Many areas of science well beyond atomic physics are also concerned with the quantum mechanical FBP. Therefore, this research is relevant to a broad range of disciplines in science including nuclear physics, chemical physics, plasma science, and accelerator physics. Students working on this project will gain research experience with a broad range of experimental atomic physics technologies and theoretical analysis methods. Kinematically complete experiments will be performed that address two major themes. First, the reaction dynamics will be investigated for collisions under a broad range of conditions including some regimes with electron speeds close to the projectile speed. Second, projectile coherence effects, which concern a fundamental aspect of quantum mechanics, will be studied. Such experiments simultaneously determine the momentum vectors of all involved particles, i.e. the scattered projectiles, any ejected electron, and the recoiling residual target ions. From the data, reaction probabilities (cross sections) will be extracted as a function of numerous parameters. The data will provide sensitive tests of sophisticated theoretical models that depend on the transverse coherence length of the projectile beams. To better test these models the divergence of the beams, and hence the de Broglie wave coherence for the projectiles, will be manipulated in the experiment. In this way the impact of the projectile wave properties on the few-body dynamics in charged-particle interactions with atoms will be studied.