  Photoinduced melting of charge order is calculated by using the exact
many-electron wave function coupled with classically treated phonons in the
one-dimensional quarter-filled Hubbard model with Peierls and Holstein types of
electron-phonon couplings. The model parameters are taken from recent
experiments on (EDO-TTF)_2PF_6 (EDO-TTF=ethylenedioxy-tetrathiafulvalene) with
(0110) charge order, where transfer integrals are modulated by molecular
displacements (bond-coupled phonons) and site energies by molecular
deformations (charge-coupled phonons). The charge-transfer photoexcitation from
(0110) to (0200) configurations and that from (0110) to (1010) configurations
have different energies. The corresponding excited states have different shapes
of adiabatic potentials as a function of these two phonon amplitudes. The
adiabatic potentials are shown to be useful in understanding differences in the
photoinduced charge dynamics and the efficiency of melting, which depend not
only on the excitation energy but also on the relative phonon frequency of the
bond- and charge-coupled phonons.
