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Stimuli responsive polymersomes: Small Angle Neutron Scattering studies
May 27 14:30 - 15:30
- Diblock copolymers can self-assemble in solution in stable and robust polymersomes (vesicles),...
To deuterate or not to deuterate? That is the question
June 03 14:30 - 15:30
- Accepted wisdom when performing diffraction experiments with neutrons is to deuterate the...
Static and dynamic properties of a strong-leg spin-ladder
June 17 14:30 - 15:30
- The AF S = 1/2 Heisenberg spin ladder belongs to the simplest quantum magnets, yet disclosing the...
After the discovery of neutrons, scientists did experiments on first little neutron sources. Otto Hahn used the combination of a radioactive alpha particle emitter and beryllium to obtain neutrons. Hahn let the free neutrons collide with the heavy element uranium. Hahn hoped to create an even heavier nucleus by the neutron capture. Instead, he found nuclei with smaller masses in 1939.
Lise Meitner, nuclear physist and colleague of Hahn, found the only logical explanation: The uranium nuclei did not gain weight by capturing neutrons, but were split in smaller nuclei caused by the neutron capture. The fission by neutrons was discovered, and Otto Hahn received the nobel prize in chemistry in 1944.
Fissuring uranium with the mass number 235 yields two medium weight nuclei. At the same time two to three fast, high-energy neutrons are released, who are moderated by e.g. cooling water. These moderated neutrons themselves fissure more uranium nuclei in a chain reaction.
Free neutrons can also be generated by spallation. Accelerated particles (usually protons) are shot towards atoms and knock out neutrons.