We report on the ultrafast dynamics of charge order and structural response
during the photoinduced suppression of charge and orbital order in a
mixed-valence manganite. Employing femtosecond time-resolved resonant x-ray
diffraction below and at the Mn K absorption edge, we present a method to
disentangle the transient charge order and structural dynamics in thin films of
Pr0.5Ca0.5MnO3. Based on the static resonant scattering spectra, we extract the
dispersion correction of charge ordered Mn3+ and Mn4+ ions, allowing us to
separate the transient contributions of purely charge order from structural
contributions to the scattering amplitude after optical excitation. Our finding
of a coherent structural mode at around 2.3 THz, which primarily modulates the
lattice, but does not strongly affect the charge order, confirms the picture of
the charge order being the driving force of the combined charge, orbital and
structural transition