  Surface force apparatus (SFA) and atomic force microscopy (AFM) can measure a
force curve between a substrate and a probe in liquid. However, the force curve
had not been transformed to the number density distribution of solvent
molecules (colloidal particles) on the substance due to the absence of such a
transform theory. Recently, we proposed and developed the transform theories
for SFA and AFM. In these theories, the force curve is transformed to the
pressure between two flat walls. Next, the pressure is transformed to number
density distribution of solvent molecules (colloidal particles). However, pair
potential between the solvent molecule (colloidal particle) and the wall is
needed as the input of the calculation and Kirkwood superposition approximation
is used in the previous theories. In this letter, we propose a new theory that
does not use both the pair potential and the approximation. Instead, it makes
use of a structure factor between solvent molecules (colloidal particles) which
can be obtained by X-ray or neutron scattering.
