Zoom on the effect of thermohaline mixing between the thermal pulses number 7 and 9 for the 2.5 M_⊙ rotating model at Z_⊙. (Bottom) Kippenhahn diagram. The hatched zone is the convective envelope; the blue shaded region corresponds to the layers where the thermohaline instability develops; the green and blue dashed lines surround the hydrogen and the helium burning shell respectively (in both cases, the dotted lines show the region of maximum nuclear energy production). (Middle) Evolution of the surface ⁷Li abundance (full line) and ¹²C/¹³C ratio (dashed line). (Bottom) Evolution of the surface ³He abundance (in mass fraction).