The s-Process (2) ...

The s-process refers to a sequence of neutron capture reactions interspersed with beta decay to produce heavier elements where the rate of neutron capture is slow because the number of neutrons that are around (the flux) is low. We can illustrate by considering an iron nucleus subjected to a source of neutrons:

In this example, iron-56 captures a neutron to become iron-57, it captures a neutron to become iron-58, and it captures a neutron to become iron-59. But iron-59 is sufficiently unstable that it is likely that it beta decays to cobalt-59 before it can capture another neutron. The beta decay releases an antineutrino and a negative beta particle (which is just an electron, but it is called a beta particle when it is produced in beta decay).

This sequence produces an isotope of cobalt, the next atomic number (27) beyond iron. Now the cobalt-59 nucleus can absorb neutrons and finally beta decay to produce an isotope of the next atomic number (28, which is nickel), and so on. By this process, heavier elements can be built up slowly if a source of neutrons and the "seed nuclei" (iron in this case) are available.