  A method is described for using resonant x-ray scattering to separately
quantify the charge (valence) modulation and the strain wave associated with a
charge density wave. The essence of the method is a separation of the atomic
form factor into a "raw" amplitude, fR(w), and a valence-dependent amplitude,
fD(w), which in many cases may be determined independently from absorption
measurements. The advantage of this separation is that the strain wave follows
the quantity |fR(w) + <v> fD(w)|^2 whereas the charge modulation follows only
|fD(w)|^2. This allows the two distinct modulations to be quantified
separately. A scheme for characterizing a given CDW as Peierls-like or
Wigner-like naturally follows. The method is illustrated for an idealized model
of a one-dimensional chain.
