Selective excitation of coupled CO vibrations on a dissipative Cu(100) surface by shaped infrared laser pulses

In a previous paper [Beyvers et al., J. Chem. Phys. 124, 234706 (2006)], the possibility to mode and state selectively excite various vibrational modes of a CO molecule adsorbed on a dissipative Cu(100) surface by shaped IR pulses was examined. Reduced-dimensionality models with stretching-only coordinates were employed to do so. This model is now extended with the goal to include rotational modes. First, we present an analysis of the bound states of the adsorbed CO molecule in full dimension; i.e., six-dimensional eigenstates are obtained by diagonalizing the six-dimensional Hamiltonian containing the semiempirical potential of Tully et al. [J. Vac. Sci. Technol. A 11, 1914 (1993)]. This is achieved by using a contracted iterative eigensolver based on the coupled two-term Lanczos algorithm with full reorthogonalization. Reduced-dimension subsystem eigenvectors are also computed and then used to study the selective excitation of the molecule in the presence of dissipation within the density matrix formalism for open systems. In the density matrix propagations, up to four degrees of freedom were included, namely, r (the C-O distance), Z (the molecule-surface distance), and phi and theta (the azimuthal and polar angles of the molecular axis with respect to the surface). Short, intense laser pulses are rationally engineered and further refined with optimal control theory, again with the goal for mode and state selective excitation. Also, IR-laser induced desorption is studied. For the calculations, the previous two-mode (r,Z) dipole surface is extended to include the angular dependence and the model for the coupling of the molecule to the surface electronic degrees of freedom is refined.