The cosmic-ray isotopes

Aspects and implications of isotopic abundance measurements are discussed, taking into account the elemental abundance distribution of the cosmic radiation and the solar system abundances normalized to C. An interesting outcome of observations on cosmic ray isotopes is the determination of the span of time that elapses between nucleosynthesis and acceleration of the particles. This has an immediate bearing on the question whether explosive nucleosynthesis and particle acceleration occur simultaneously, or whether these two phases in the production of cosmic rays are separate. The absence of Co-57, Ti-44, and Ni-59 with K-capture decay rates of approximately 1 yr, 50 yr, and 100,000 yr respectively in the cosmic ray flux would indicate that the time between nucleosynthesis and acceleration would be greater than 1, 50, or 100,000 yr, respectively.