Serving the Reich by Philip Ball

Author:Philip Ball [Ball, Philip]
Language: eng
Format: epub
Publisher: University of Chicago Press
Published: 2014-02-05T16:00:00+00:00

Lise Meitner, seated second from right at the 1933 Solvay conference. Irène Joliot-Curie is seated second from left, and her mother Marie Curie fifth.

Fermi was wrong about his trans-uranics, but the principle of making elements by neutron capture was sound. Hahn and Meitner, assisted by a young German chemist named Fritz Strassmann, began to gather evidence for new types of radioactive substances created from uranium: maybe other isotopes of that element, maybe new elements in the uncharted territory beyond. There was something here, but it was hard to interpret.

Strassmann joined the KWIC in 1929 as a student intending to seek subsequent employment in industry, but he soon decided that he would rather stay and do fundamental research. His career after 1933 shows how difficult it could be for a young researcher not protected by wealth or status openly to oppose the National Socialists. He despised the regime and his refusal to join any Nazi organizations prompted his resignation from the Nazi-controlled Society of German Chemists. As a result he was blacklisted from jobs in academia and industry, and denied promotion or proper pay at the chemistry institute. Consequently, he was pitifully poor and malnourished, and considered himself lucky when Hahn and Meitner managed to find an assistantship for half-pay in 1935: ‘I value my personal freedom so highly that to preserve it I would break stones for a living’, he attested. His resistance to the Nazis never flagged; during the war, he and his wife hid a Jewish friend in their apartment. In retrospect Strassmann looks more heroic than most of his illustrious colleagues.

Splitting apart

After Lise Meitner’s flight from Germany in July 1938, Hahn and Strassmann continued the uranium studies. But without Meitner’s expertise they had difficulty interpreting what they saw. They found that uranium could be transformed by neutron bombardment into three radioactive substances that seemed chemically similar to barium, and which they therefore concluded must be isotopes of radium (which shares a column with barium in the periodic table). That, however, implied two alpha particles must be emitted at once from uranium, which had never before been seen. They wrote to Meitner, now in Stockholm, who replied that it did not seem credible. In fact, these forms of ‘radium’ resisted all attempts to separate them from barium itself—as if they were indeed nothing other than barium.*8

But that was even more absurd. Barium (element 56) had barely half the mass of uranium (element 92). There was a consensus that transmutations happened only a little at a time: a radioactive decay would turn one element into another very nearby in the periodic table, either by losing two protons (alpha decay) or gaining one (beta decay). You couldn’t get straight to barium from uranium—could you?

Yet Hahn and Strassmann were running out of other explanations for their weird findings. On 19 December Hahn wrote to Meitner in Stockholm:

Perhaps you can suggest some fantastic explanation. We understand that [uranium] really can’t break up into barium . . . So try to think of some other possibility .

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