Accelerator mass spectrometry measurement of the reaction ³⁵Cl(n,gamma)³⁶Cl at keV energies

The nuclide ³⁵Cl can act as a minor "neutron poison" in the stellar slow neutron capture process. Neutron activation combined with accelerator mass spectrometry (AMS) was applied to measure the (n,gamma) cross section of ³⁵Cl for neutron spectra simulating Maxwell-Boltzmann distributions of kT ~30 keV and 40 keV, respectively. The neutron activations were performed at the Karlsruhe Van de Graaff accelerator and at the superconducting linear accelerator of the Soreq Applied Research Accelerator Facility utilizing the ⁷L(p,n)⁷Be reaction. AMS measurements of the irradiated samples were performed at the 3 MV Vienna Environmental Research Accelerator, the 6 MV tandem accelerator at the Dresden AMS facility, and the 14 UD tandem accelerator of the Australian National University in Canberra. Our method is independent of previous measurements. For an energy of kT=30 keV, we report a Maxwellian averaged cross sections of 8.33(32) mb. Using this new value in stellar isotopic abundance calculations, minor changes for the abundances of ³⁵Cl, ³⁶Cl and ³⁶S are derived.