This makes it very important to have comprehensive tables of nuclear masses that include all possible nuclides in the silicon to iron region, even those that are impossible to observe in experiments. The experimental masses are also provided, when available. In addition, we have an interactive HTML form called qtool that allows you to compute reaction Q values from experimental masses backed up by calculated masses when needed. Therefore, it would only be expected to take place in second-generation stars that collapsed out of the residue of a previous supernova explosion. Analysis shows that the abundance of a nuclide should be inversely proportional to its cross section for absorbing a neutron averaged over the neutron spectrum present during the s-process.
Some uncertainties remain, and they are good targets for new measurements.
This process cannot explain all of the isotope ratios observed, and the r-process was developed to solve the problem. This process clearly requires a huge neutron flux, and it is assumed to take place during the explosion of a supernova. An analysis of this process indicates that the relative abundance of each nuclide should be proportional to the decay lifetime of its progenitor on the r-process line. Theory comes to the rescue. The same FRDM that gives the calculated nuclear masses can also be used to estimate beta-decay lifetimes.