Stellar neutron capture on 180Tam. II. Defining the s-process contribution to nature's rarest isotope

The contribution of the slow neutron capture process (s process) to the solar 180Tam abundance has been investigated on the basis of new experimental information. Measured neutron capture cross sections of 180Tam and the corresponding Maxwellian averaged (n,γ) rates were important for defining the s abundance of 180Tam, and the result of a recent photoactivation experiment was providing an estimate of its half-life at the temperatures of the s-process site. Following the s-process network with stellar evolutionary models from the premain sequence through the asymptotic giant branch phase, it was found that the produced 180Tam survives the high temperatures during He shell flashes because of the fast convective mixing, which provides an efficient means for transporting freshly synthesized matter into cooler, outer zones. Accordingly, 180Tam appears to be predominantly of s-process origin