Although institutionally under the care of a corrupt and incompetent administration, Romanian physics of the 1940s could be proud of several first-class personalities, such as Şerban Ciceika, George Manu, Radu Grigorovichi, Horia Hulubei, Yevhen Bederau. The first two with brilliant doctorates in the West – Heisenberg and Marie Curie respectively – did not receive chairs upon their return to the country, as would be expected in any responsible political system, but were marginalized as humble assistants, without the right to teach any course Hryhorovychi, who studied at the university – the former Austrian University – in Chernivtsi under the leadership of Baderau and Herbert Mayer, faced a severe shortage of experimental equipment when he moved to Bucharest. Hulubey, having just returned from France, exhausted himself trying to create a scientific research institute in Cluj, which would be ready… on the eve of the Viennese dictatorship.

From meeting Otto Hahn to separating uranium isotopes

Despite the instability of laboratories and limited international contacts, special literature came to the country, and the above-mentioned personalities were fully aware of the significance in which nuclear physics is developing – still relatively often, equally “atomic”. It is probably not by chance that in 1940 Hryhorovychy, encouraged by Baderau, held a popularization conference called “Separation of Isotopes” and another, more specialized, with the same name, addressed to members of the university laboratory. Another lecture the same year mentioned “Low Pressure Production and Measurement,” a technique familiar to both Baderau and Hryhorovych.

Shortly after Hulubei became rector of the University of Bucharest, in 1941, Otto Hahn, the pioneer of nuclear fission, a phenomenon that would lead to peaceful and military uses of nuclear energy, visited Romania. Khan’s earlier research partially coincided with that of Khulubey, both of whom attempted to isolate the eka element (an element missing from the periodic table) that would be accepted (in 1949) by the international scientific community as francium. During his visit to Romania, Han is surrounded by Manu and Hryhorovych, and the discussions between them, caused by the latter half a century later, are especially interesting [1]. A byproduct of the visit was the famous portrait of Gan by the pen of Manu [2].

A few months later, Khulubey brings Khan back for a visit, during which he holds several conferences in Berlin and visits laboratories and scientific equipment factories in Germany. The hypothesis that Khan’s visit may have been motivated, at least in part, by the Reich’s attempt to test the interest of the Romanian nuclear forces in any possible cooperation with Germany remains only a conjecture; we do not know any clues about the meaning of this hypothesis.

Instead, it is very interesting to remember how, completely isolated from the top-secret research related to the production of the atomic bomb, Romanian physicists follow the problem and offer – in great secrecy – original approaches. Specifically, this is the method of isotope separation proposed by Hryhorovych, following the guidance received from Bederau to address this topic, as we have seen above. It was known that in the American project isotopes [3] they were separated by thermal diffusion: light isotopes leave the heated container faster than heavy isotopes. The purpose of isotope separation was to obtain a high concentration of the fissile isotope of uranium, which, through a chain reaction, caused the explosion of an atomic bomb. This is how Hryhorovychi talks about the development of his research:

Getting to the point, I didn’t like the idea of ​​separating isotopes using thermal diffusion. Another idea seemed more interesting to me: when two molecular beams of the same composition, formed by a mixture of isotopes that will be separated, collide, a certain isotope effect should occur. I thought that, given the wave nature of the molecules, there must be some kind of interference that gives certain scattering angles, maxima and minima in the isotopic composition of the scattered rays. That is, after certain angles, the maximum concentration of the isotope in the scattered beam should be reached, and after other angles – the minimum.

We went to Sherban Shytseika and asked him to tell us about the theory of this phenomenon. Ticeika was a little surprised, he told us that everything is complicated, that we should not think that molecules are balls, that their collision is very difficult. Finally he asked us as usual [4], a week of rest. Mott’s book on collision theory was of course also used. A week later, Tițeica came with an answer from which I understood little, except that the phenomenon was possible in principle.

Read the rest on Contributors.ro