A Process in Search of an Environment: The \(r\)-Process
While the \(s\)-process can be described as a low neutron flux occurring over a long period of time, the \(r\)-process can be described as the opposite, namely, irradiation by a high neutron flux for a very short time. Hence, while the \(s\)-process could be described as a quiet, slow, hydrostatic evolution, the \(r\)-process is usually associated with the most violent phases in stellar life—the explosion that puts an end to the ‘normal’ life of the star. It seems that no in-between process exists, only the two extremes. Notwithstanding, problems with the explosion scenario have led astrophysicists to ponder on less violent circumstances where a milder variant of the \(r\)-process might take place. But whatever the situation, we are now looking for an extreme source of neutrons in an expanding environment. The adjective ‘extreme’ refers to the nuclear properties while the requirement of expansion refers to the astrophysical site, so that the synthesized isotopes can be ejected into space. Alpher, Bethe, and Gamow considered the Big Bang to be just such an explosive situation, but in this specific case we are supposedly immersed in the products.