A Time Scale for the Mixing Process in S-Type Stars.

It is shown that neutron production in a late-type star, on the scale proposed by Cameron, leads to a drastic lowering of the Nb/Zr abundance ratio Mter removal of the material from the neutron-producing region, the ratio rises again, due to decay of 9 X 10 years Zr93 to Nb93. Thus this ratio can be used, in principle, to calculate the mixing time from observational data. The application, limitations, and principal sources of error of the method are discussed.