Following the triple-alpha process to form 12C (see the previous problem), a variety of...

Following the triple-alpha process to form ¹²C (see the previous problem), a variety of nuclear reactions can form heavier nuclide masses. In one of them , , the temperature must be greater than about 3 billion K. (a) Why does the temperature have to be so high? (b) Calculate how much energy is released in the reaction. It is reactions like this that allow nuclei in the iron region to be formed.

Problem 36

There is a bottleneck in producing masses higher than ⁴He, because there are no mass-5 or mass-8 stable nuclides. For older stars with high densities and high temperatures (T >100 million K), three alpha particles can form 12C. This occurs by two alpha particles first forming ⁸Be, and ⁸Be reacting with another alpha particle to form ¹²C before ⁸Be can decay back to two alpha particles. (a) Explain why this has to happen for very hot stars and high density. (b) Calculate how much energy is given up when three alpha particles form ¹²C.