A NEW ISOTOPE OF URANIUM

In the March issue of The Physical Review for 1947 there appeared a very brief note by Seaborg, Gofman, and Stoughton** reporting their discovery in 1941–1942 of a new isotope of uranium, \(\mathrm{U}^{233}\). This isotope is formed when thorium is irradiated with slow neutrons as a result of the following processes:

\[ \mathrm{Th}^{232}(n,\gamma)\mathrm{Th}^{233} \xrightarrow[\beta]{23.5\ \text{min.}} \mathrm{Pa}^{233} \xrightarrow[\beta]{27.4\ \text{days}} \mathrm{U}^{233}. \]

The authors investigated the radioactive properties of the new isotope and established its ability to undergo fission under the action of neutrons. The experiments were carried out with small quantities of \(\mathrm{U}^{233}\) (3.8 and 0.8 micrograms). This exhausts the information contained in the note. Without doubt, the study of the properties of \(\mathrm{U}^{233}\) is of great interest.

I. Sh.

* If one takes \(\mu \rho = 2.7896\).
** G. T. Seaborg, J. W. Gofman and R. W. Stoughton, Phys. Rev. 71, 378 (1947).