  The Cygnus Loop has been the focus of substantial debate concerning the
contribution of charge exchange (CX) to supernova remnant (SNR) X-ray emission.
We take advantage of a distinct feature of CX, enhanced K{\alpha} forbidden
line emission, and employ the energy centroid of the OVII K{\alpha} triplet as
a diagnostic. Based on X-ray spectra extracted from an extensive set of Suzaku
observations, we measure the energy centroid shifts of the triplet on and off
the shock rim of the remnant. We find that enhanced forbidden to resonance line
emission exists throughout much of the rim and this enhancement azimuthally
correlates with non-radiative H{\alpha} filaments, a tracer of strong
neutral-plasma interaction in the optical. We also show that alternative
mechanisms cannot explain the enhancement observed. These results demonstrate
the need to model the CX contribution to the X-ray emission of SNRs,
particularly for shocks propagating in a partially neutral medium. Such
modeling may be critically important to the correct measurements of the
ionization, thermal, and chemical properties of SNRs.
