# How to form Copper from Calcium in a supernova explosion?

What are the reasonable chain of reactions to form copper (63, 29) from ca(40, 20) during supernova explosion? And how it will happen? I do not understand the theory behind it. I thought that the reaction will end at Iron and now it does not make sense to me.

• Could you give some context as to why you think there is a direct link between copper and calcium. Apr 16 '16 at 20:28

The source of the neutrons is still somewhat debated, it could either be from the decay of $^{13}$C in relatively low-mass asymptotic giant branch stars or is more likely from the decay of $^{22}$Ne in more massive evolved stars (e.g. Pignatari et al. 2010).
Below you can see a typical route for producing copper from $^{56}$Fe. The axes of the plot are neutron number on the x-axis and proton (atomic) number on the y-axis. Three neutron captures are followed by a beta decay, a neutron capture, a beta decay, then 3 more neutron captures followed by another beta decay to form $^{63}$Cu.
The net process is $$^{56}{\rm Fe} + 7n \rightarrow \ ^{63}{\rm Cu} + 3e + 3\bar{\nu}_e$$