Cerium 140 into Cerium 141 via use of ceria powder? I was reading a PDF Cerium 141 production, that stated cerium 141 productions via ceria powder. My question is how is the Cerium 141 actually created via using standard ceria powder?
 A: As the article states, it's done by exposing the $^{140}\text{Ce}$ to neutrons.
Using the Evaluated Nuclear Data File site (https://www.nndc.bnl.gov/exfor/endf00.jsp) one can pull up the neutron cross sections. Below are shown the total cross section (all neutron scattering paths) and the $^{140}\text{Ce}$ (n,$\gamma$) $^{141}\text{Ce}$ cross section. Clearly thermal neutrons from a reactor are the way to go. 

As for the resulting gamma spectrum, you go to the Evaluated Nuclear Structure Data File tab (https://www.nndc.bnl.gov/ensdf/) and pull up the measured energies and intensities of the gamma from the reaction:

As a bonus, it actual is hard to make lots of $^{141}\text{Ce}$ since it turns out that the $^{141}\text{Ce}$ (n,$\gamma$) $^{142}\text{Ce}$ cross section is more than 10x larger than the $^{140}\text{Ce}$ (n,$\gamma$) $^{141}\text{Ce}$ cross section:

This means that once you get to about 10 percent $^{141}\text{Ce}$ in your powder, you are turning it into $^{142}\text{Ce}$ as fast as you are making it.
