Measurement of the Rb-85 and Rb-87 capture cross sections for s-process studies

The neutron capture cross sections of Rb-85 and Rb-87 using the TOF technique are measured. From the differential data, Maxwellian-averaged capture cross sections are computed as a function of thermal energy kT = 5-100 keV. The results are combined with previous data to perform s-process calculations, especially with regard to the Kr-85-Rb-86 branchings. Solar s-process abundances are reproduced with a two-component phenomenological model below mass number 90, a single-flux weak s-process, and a pulsed s-process characterized by exponentially distributed neutron exposures. The solar s-process abundances, as well as s-process abundances from Ba stars and the Murchison meteorite, are studied in the framework of the asymptotic giant branch models. Constraints are derived with regard to the properties of the neutron pulses for a description of the empirical s-process data.