  The stratification near the base of the Sun's convective envelope is governed
by processes of convective overshooting and element diffusion, and the region
is widely believed to play a key role in the solar dynamo. The stratification
in that region gives rise to a characteristic signal in the frequencies of
solar p modes, which has been used to determine the depth of the solar
convection zone and to investigate the extent of convective overshoot. Previous
helioseismic investigations have shown that the Sun's spherically symmetric
stratification in this region is smoother than that in a standard solar model
without overshooting, and have ruled out simple models incorporating
overshooting, which extend the region of adiabatic stratification and have a
more-or-less abrupt transition to subadiabatic stratification at the edge of
the overshoot region. In this paper we consider physically motivated models
which have a smooth transition in stratification bridging the region from the
lower convection zone to the radiative interior beneath. We find that such a
model is in better agreement with the helioseismic data than a standard solar
model.
