Is it an artifact? (I have drawn the black line). Or can anybody explain it theoretically?
The plot is the "235U Chain 14MeV" provided in the website https://www-nds.iaea.org/ Some sources call it "hot fission" to distinguish it from "thermal" and "fast". Vertical scale is logarithmic, from 10 to 1E-4. The peak at A=135 is 6.6 (I guess it means 6.6%), the jump is from 1.657 to 0.595, a factor 2.
To produce it, go to the LiveChart of Nuclides, select the 235U and the tab "fission yields". A new window pops up, allowing to select either thermal, fast, or 14 MeV -neutrons, I guess-. I do not think it is an artefact because smoother jumps can be seen in other plots; it is a fine visualisation from IAEA Nuclear Data Services, and it is only a pity that they seem to have data only for a few fissions. It seems that JEFF only has "hot" data for 233U, 235U, 238U and 232Th, inherited from UK libraries.
I do not think it to be due totally to magic number neither, because it should be (the counterpart of) a nucleus with about 235-147=88 nucleons and then only the simple magic N=50 Z=38 is in the range, no double magic items. Besides, the plot of decay rates for thermal neutrons offered in the same website looks as its main dependency is in Z+N.
Ah, independently of the explanation, I'd be happy with some guide telling how to produce it from the raw files (JEFF 3.2 probably?) as I would like to produce the NZ-plane view. Thanks
Update: It seems that the UK chain yield data, from which the JEFF data comes, was fitted with a procedure called "Five Gaussians". RW Mills thesis is available online: http://etheses.bham.ac.uk/4353/1/Mills95PhD.pdf