What does "iron peak" mean in the collapse of a critical mass iron core?

[GIASAL]

The collapse of the critical-mass iron core accelerates rapidly. This runaway is driven principally by photodissociation of iron-peak nuclei, Fe(γ, α), and by electron captures

What does "iron peak" mean?

 

[phyzguy]

If you look at the binding energy per nucleon of atomic nuclei, it peaks in the vicinity of iron. You can get energy by fusing nuclei lighter than iron or by fissioning nuclei heavier than iron, but once nuclear fusion has arrived at nuclei near iron, no more energy can be obtained. Since no more energy is available from fusion, there is no radiation pressure to support the core against gravity, and the core collapses.

 

[GIASAL]

Is the binding energy per nucleon clearly equal to the energy required to extract a nucleon?

 

[Astronuc]

Is the binding energy per nucleon clearly equal to the energy required to extract a nucleon?

No. The binding energy per nucleon (BEN) is the total binding energy divided by the number of nucleons. However, as the number of nucleons increases, the BEN approaches the binding energy of the last nucleon (neutron). One can look at the gamma energy of an emitted gamma when a nucleus absorbs a neutron (radiative capture).

For example, the energy required to dissociate a deuteron is ~2.2246 MeV. The binding energy per nucleon is ~2.2246/2 = 1.1123 MeV/n.

For ⁶²Ni has a total binding energy of about 545.3 MeV for 62 nucleons, for a BEN = 8.795 MeV/nucleon, and the binding energy of the last neutron is about 10.6 MeV.

The total binding energy is given the total mass of the protons and neutrons minus the mass of the nucleus of interest. For ⁶²Ni, Z = 28, N = 34, where A = Z + N = 62.
https://phys.libretexts.org/Bookshelves/University_Physics/University_Physics_(OpenStax)/University_Physics_III_-_Optics_and_Modern_Physics_(OpenStax)/10:__Nuclear_Physics/10.03:_Nuclear_Binding_Energy

Take the mass of ⁶¹Ni = 60.931060 u and the mass of a neutron 1.008665 u and subtract the mass of ⁶²Ni = 61.928349, which gives a binding energy of 0.011376 u, or
0.011376 u * 931.494 MeV/u ~ 10.6 MeV
Ref: https://www.chem.ualberta.ca/~massspec/atomic_mass_abund.pdf

An alternative table is https://physics.nist.gov/cgi-bin/Compositions/stand_alone.pl

 

[phyzguy]

Take the mass of 62Ni = 60.931060 u and the mass of a neutron 1.008665 u and

I think you mean the mass of 61Ni = 60.931060 u

 

[Astronuc]

I think you mean the mass of 61Ni = 60.931060 u

Yes. Correction made.