A contribution to improvement of the nuclear data concerning alpha decay of U

Compared to other alpha-particle emitting nuclides, for those with long half-lives (T_1/2>10⁶ years), there is generally some inconsistency and inaccuracy in the associated nuclear data. However, these radionuclides play a major role in modern society and, for a number of reasons, are the subject of widespread interest. The study of their alpha decay, which is more difficult than in the case of the other nuclides, enables knowledge of their nuclear data to be increased. In the present paper, we accordingly consider one of the most well known ones: ²³⁵U. Using a quasi mono-isotopic deposit of ²³⁵U obtained by electromagnetic separation, we have studied the alpha-particle decay of ²³⁵U using a high-energy resolution spectrometer developed in our laboratory. The stability of the spectrometer made it possible to perform long measurements which is crucial in the case of ²³⁵U. The Colégram program, with a new fit criterion to better take into account peaks of low statistical significance, was used to extract the data (alpha-particle emission probabilities and energies). Monte-Carlo simulations carried out in the context of this work were also used to corroborate the data obtained. Finally, thirteen alpha-particle emissions from ²³⁵U were measured, from which only ten were previously observed and measured. This work has substantially reduced the uncertainty concerning alpha-particle emission probability and energy values and has resolved some of the ambiguities concerning the ²³⁵U disintegration scheme to ²³¹Th.