Positron Emission Tomography (PET) is a functional diagnostic used to determine the location of areas of accelerated metabolic activity. This is accomplished by attaching a radioisotope (positron emitter) to a glucose molecule. An excess of positrons collect where the glucose collects. The location is determined from the back-to-back gamma rays produced when a positron annihilates with an electron.
Dissociative electron attachment (DEA) is a process by which an electron can fragment a molecule. This process is known to be a mechanism in the damage of DNA and can occur well below the ionization potential of the molecules. The similarities between electron and positronium scattering suggest the electron plays a dominant role in the scattering process. Thus, it is likely that a positronium atom can be fragmented via DEA with a molecule freeing the positron.
Before the positron and electron annihilate, they form the exotic atom, positronium, which is a temporary bound state between an electron and a positron. Very little is known about the scattering of positronium and molecules. Work to date indicates that the positronium atom scatters like an electron of equal velocity. This project will focus on the fragmentation of the positronium atom by molecules.
The project will consist of using the low-energy positron beamline to produce a positronium beam. Scattering and fragmentation data will be obtained for a number of molecular targets. The objective of this project is to determine the extent of DEA in positronium scattering with molecules.