Does Alpha Process Produce Bismuth?

Question

In the book "Horizons: exploring the universe-Cengage learning (2018)", p200, it states that:

Helium fusion produces carbon, and some of the carbon nuclei absorb helium nuclei to form oxygen. A few of the oxygen nuclei can absorb helium nuclei and form neon and then magnesium. Some of these reactions release neutrons, which, having no charge, are more easily absorbed by nuclei to gradually build even heavier nuclei. These reactions are not important as energy producers, but they are slow-cooker processes that form small traces of heavier elements right up to bismuth with atomic weight 209, nearly four times heavier than iron. Many of the atoms in your body were produced this way.

Base on my question previously, I assume we are talking about the alpha process here. And when I check the Wikipedia of the Alpha Process, it says that the alpha process ends at $^{56}_{28}\mathrm{Ni}$ due to photodisintegration, but as the suggests, the process should produce $^{209}_{83}\mathrm{Bi}$. The question is, why do Bismuth, an atom with atomic number $83$ are produced here? Shouldn't atom like $^{}_{82}\mathrm{Pb}$ with even atomic number being produced here?

Answer 1

Bismuth is produced via the s-process.

It is the slow absorption of neutrons that can produce heavier elements beyond the peak of the binding energy per nucleon curve at iron. The alpha process isn't capable of producing much of anything beyond nickel.

Answer 2

I'll (attempt to) add to @ProfRob's answer:

The alpha process isn't capable of producing much of anything beyond nickel.

The alpha particles (helium nuclei) and the target nuclei are both positively charged and face a huge barrier due to electrostatic (Coulomb) repulsion.

They successfully tunnel through this Coulomb barrier from time to time only because it is energetically favorable. This is generally called nuclear fusion.

Once you get well above iron¹ there is no longer an energy advantage. The nuclei are in a lower energy state separate from each other. You'd need to add energy to the system to make them stick. So the coulomb barrier tunneling will be unsuccessful unless you have high energy helium nuclei. We do that on Earth with particle accelerators, generally to tens of MeV energy to get it to happen.

That's why alpha decay happens for the much heavier nuclei. Many of them will spontaneously "spit out" alpha particles; getting rid of them. They are in no mood to accept some low energy alpha particle knocking at the door. We use this spitting out of energetic alpha particles for heaters in spacecraft like Mars rovers Curiosity and Perseverance and deep space probes like the Voyagers and even on the moon.

They are called radioisotope thermoelectric generators and are a good concrete example of nuclei much heavier than iron having no interest whatsoever in accepting more alpha particles.

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¹Thanks to @ProfRob and @PM 2Ring for their helpful comments. For people who call anything bigger than helium "metal" I was surprised at the sudden attention to detail ;-)