  We derive a semi-analytic solution for the structure of conduction-mediated
transition layers above an X-ray illuminated accretion disk, and calculate
explicitly the X-ray line radiation resulting from both resonance line
scattering and radiative recombination in these layers. The vertical thermal
structure of the illuminated disk is found to depend on the illuminating
continuum: for a hard power law continuum, there are two stable phases
connected by a single transition layer; while for a softer continuum, there may
exist three stable phases connected by two separate transition layers, with an
intermediate stable layer in between. We show that the structure can be written
as a function of the electron scattering optical depth through these layers,
which leads to unique predictions of the equivalent width of the resulting line
radiation from both recombination cascades and resonance line scattering. We
find that resonance line scattering plays an important role, especially for the
case where there is no intermediate stable layer.
