Positron Research Group -|-|- St Olaf College, Northfield, MN, USA


What is a Positron? Crash Course for Beginners

Gas Scattering Experiment
Micelle Experiment
About Our Group
Frisbee Golf

Positron Research Group
Science Center 155
1520 St. Olaf Avenue
Northfield, MN 55057

Dr. Jason Engbrecht
507-646-3968 FAX


Anna Legard '08

Dan Endean '09

David Green '09




A rough sketch of a micelle, showing a 2D slice of a sphere of amphiphiles with polar head groups (blue) and hydrocarbon chains (green).

Micelles are aggregates made up of amphiphiles. Amphiphiles have a water-soluble head group and a hydrophobic hydrocarbon chain. The amphiphiles group together naturally in solution, creating micelles in the form of bilayers, spheres, ellipsoids, cylinders, and other shapes. The hydrophobic carbon chains come together to make the inner core of a micelle absent of solution.

In our experiment, we will use sodium dodecyl sulfate (SDS) to create micelles in a solution of water. We will then place a radioactive source in the solution to create positronium atoms. The positronium atoms will naturally diffuse into the micelles. The average Ps lifetime inside the micelles will differ from the average Ps lifetime in the water. After collecting data on the various positronium components, we should be able to fit our data to determine certain characteristics of the micelles, such as their average radius and aggregation number. [1]

This work is being done in collaboration with Dr. Anne Walter, a faculty member in the St. Olaf Biology Department.