Lise Meitner

Lise Meitner: A Life in Physics by Ruth Lewin Sime, University of California Press, 1996. 

Female, Jewish Physicist

This is a biography of an Austrian, Jewish, female nuclear physicist, who, with Otto Hahn, discovered nuclear fission. Meitner worked in Berlin at the Kaiser-Wilhelm Institute. She was an experimental nuclear physicist. She bombarded uranium atoms with neutrons. Her primary collaborator was Otto Hahn. Hahn performed the chemical isolations and chemical analyses of the results of Meitner’s physics experiments. He determined which elements were found in the products of the experiments. 

Atomic Number and Atomic Weight

The atomic number is the number of protons in the nucleus. The atomic number determines the chemical properties of the atom. The atomic weight is the sum of the number of protons and the number of neutrons in the nucleus. But in the 1920s and early 1930s, the neutron had not yet been discovered, so there was confusion among physicists regarding the atomic number and the atomic weight. Otto Hahn did not know much about nuclear physics. Hahn was slow to understand that the atomic number was more important than the atomic weight.

Radioactivity

In the early experiments, there were only small changes in atomic number and atomic weight in both bombardment experiments and spontaneous radioactivity. For example, the radioactive emission of an alpha particle (two protons plus two neutrons) decreases the atomic number by two, and the atomic weight by four. An absorption of a neutron increases the atomic weight by one, and does not change the atomic number. 

Fleeing the Nazis

Because she was Jewish, Meitner fled to Sweden when the Nazis came to power,. While in Sweden, Meitner continued to collaborate with Hahn long distance. In her absence, Hahn’s new collaborator, Fritz Strassmann, performed the physics experiments, using the experimental apparatus that Meitner had built. Meitner participated intellectually with Hahn and Strassman when they discovered nuclear fission. 

Otto Robert Frisch

In Sweden and Denmark, Meitner worked with Otto Robert Frisch on the theoretical interpretations of the fission experiments. She encouraged their collaborators Hahn and Strassman in Berlin to pursue a difficult-to-interpret experiment where bombarding uranium with neutrons seemed to produce a radium isotope with an unusual half-life.

Nuclear Fission

After the Berlin team repeated the experiment and performed a chemical analysis on the radium produced, the Berlin team found that it was not radium, but actually barium. Uranium had split into barium and krypton. They were not looking for fission. They found it serendipitously. Fission had actually been occurring for several years in various experiments before scientists had enough imagination to recognize it.

Nobel Prize

The 1944 Nobel Prize in Chemistry was given to Otto Hahn for the discovery of nuclear fission. Meitner never received a Nobel Prize. She should have received the Nobel Prize in Physics for the discovery of nuclear fission.