Charge and bonding redistribution in octatetraene driven by a strong laser field: Time-dependent Hartree-Fock simulation

The time evolution of the reduced single electron density matrix for the pi electrons in conjugated molecules in an intense laser field is calculated by numerically integrating the time-dependent Hartree-Fock equations for the Pariser-Parr-Pople model Hamiltonian. We study the field frequency and intensity dependence of the pi-electron response, the charge fluctuations with respect to the ground state, and the molecular polarization in unsubstituted and acceptor-donor substituted octatetraene, where we also examine the interaction between a permanent electric dipole moment and the laser field. Our results demonstrate the origin of large nonperturbative changes in the pi-electronic charges and bond orders (diagonal and off-diagonal density matrix elements, respectively) induced by a strong laser field. (C) 2003 American Institute of Physics.