The fission barrier of Neptunium-238

In a recent entry I have already introduced our measurement on Neptunium-238 and the first steps of the data analysis. In the last couple of weeks I could proceed so now I want to write some details about it

a) Fission probability of Neptunium-238 in the function of excitation energy. b) Sharp resonances in the fission probability and its rotational structure

In Figure (a) the data points of our measurement are indicated by blue open triangles, and open circles represent a previous, low resolution measurement. The continuous red line indicates the result of our model calculations, in which we altered the free parameters (actually the fission barrier parameters) until the theoretical line fits to the data points. As a result we got a quite good description with a triple-humped fission barrier having barrier heights of 5.5 MeV, 6.2 MeV and 6.3 MeV.

 

This result shows that the structure of Neptunium-238 and the previously examined Protactinium-232 (both odd-odd nucleus) is quite similar. The fission resonance structure which is shown in Figure (b) also supports this similarity: these resonances are in the same energy region as in the case of Protactinium-232. Actually, this means that their 3rd minimum in the potential barrier have the same depth.

The manuscript on these results have already been accepted by Acta Physica Polonica B for publication, and will be published expectedly in April.