Ever since their discovery in 1960, the origin of the relatively short-lived radionuclides, now extinct but alive in the early solar system, has been under debate. Possible scenarios are either nucleosynthetic production in stellar sources, e.g. AGB stars, Wolf-Rayet stars, novae and supernovae, with subsequent injection into the solar nebula, or production by spallation reactions in the early solar system by energetic particles from the young sun. Here we present model calculations for the second scenario, the production of the relatively short-lived radionuclides by solar energetic particle events in the early solar system. For successful modeling the cross sections for proton-, ~3He-, and ~4He-induced reactions for all relevant nuclear reactions have to be known. In addition, the modeling depends on the relative fluence contributions of protons, ~3He, and ~4He in the solar energetic particle events as well as on their energy distribution. The ability of the model calculations to simultaneously describe the observed nuclide ratios ~7Be/~9Be, ~(10)Be/~9Be, ~(26)Al/~(27)Al, ~(41)Ca/~(40)Ca, ~(53)Mn/~(55)Mn, and ~(92)Nb/~(93)Nb is presented. Special emphasis is given to the problems arising from ill-known cross sections for ~3He- and ~4He-induced reactions.
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