mfb said:
It's possible if the incoming proton has enough energy. For a rough estimate:
* consider the potential energy a proton has just before "touching" the potassium nucleus.
* consider the energy balance and calculate the minimal proton energy
Take the larger of the two values.
It's not a very likely reaction.
Rough but misleading approach.
p,γ reactions are extremely common and important. Just look up.
d+p=
3He+γ happens all the time, and very fast. And does not compete with fission... it releases energy, while the only alternative
d+p=2p+n
loses a lot.
Now look at CNO cycle:
1)
12C+p=
13N+1,95 MeV
2)
13C+p=
14N+7,54 MeV
3)
14N+p=
15O+7,35 MeV
4)
15N+p=
16O+12,13 MeV
12C+α+4,96 MeV
5)
16O+p=
17F+0,60 MeV
6)
17O+p=
18F+5,61 MeV
14N+α+1,19 MeV
7)
18O+p=
19F+7,99 MeV
15N+α+3,98 MeV
8)
19F+p=...
16O+α+8,11 MeV
In every step that provides a choice between p,γ and p,α, the latter prevails, because it is the strong process. However, four of the eight just do not have α option.
Do K-39 and K-41 preferentially undergo p,γ or p,α?
How common are p,γ processes to form Ca? Especially Ca-42?
Isotopes divisible by α - Ne-20, Mg-24, Si-28, S-32, Ar-36 and Ca-40, and their daughters Ca-44, Ti-48, Cr-52 and Fe-56 are common in world, because they form simply by α,γ. But they are not the only ones that exist.
What are the most common reactions that form Ca-42, and their proportions?
41K+p=
42Ca?
38Ar+α=
42Ca?
Any others?