The unit cell. In the present model the and vectors are constant parameters, while is the spatial variable of the Schrödinger equation describing the dynamical process.
Arrangement of the molecules in the crystal. Each molecule lays in a plane as displayed in the figure. The positions of the atomic cores are indicated at the equilibrium positions in proportion, whereas the atoms themselves are displayed schematically by circles. The two-molecule unit cell, used in the present work, is indicated by dashed lines. The and the lattice vectors are shown as dashed arrows. The small arrows along the molecular axis point to the positions of the atoms for a maximal internuclear distance of . The optimal choice of the polarization direction of the visible pump pulse is also shown.
Potential energy curves and of the molecule used in the simulations. In the present case the caging potential parameter is and is .
Schematic display of the experimental setup. Coherent intramolecular vibrations are generated by resonant electronic excitation with an ultrashort visible pulse within a thin layer of the molecular crystal. The structural changes due to the atomic motion are monitored by diffraction of a delayed x-ray probe pulse.
Unit cell scattering factors. The components and of the unit cell scattering factor are displayed for different caging potential parameters, . The pump pulse parameters are , , . The Miller indices are . The wavelength of the x-ray probe is . (a) UCSF for , 4.0, 3.5, and , and (b) UCSF for .
Time-resolved x-ray diffraction signal for different caging potential parameters . The different values are indicated next to the curves in angstroms. The Miller indices are 004. The FWHM of the x-ray pulse is . All other parameters are the same as for Fig. 5.
Unit cell scattering factors for Miller indices . The caging potential parameter is . All the other parameters are the same as for Fig. 5.
Time-resolved x-ray diffraction signal for different experimental arrangements. The corresponding Miller indices are indicated next to the curves. (a) The peak intensity of the pump pulse is and the FWHM of the x-ray probe pulse is . (b) The peak intensity of the pump pulse is and the FWHM of the x-ray pulse is .
Time-resolved x-ray signal for different pump intensities. The corresponding peak intensities are indicated next to the curves in . All the other parameters are the same as for Fig. 8(a).
Potential parameters of the molecule used in the simulations (see Ref. 20).
Coefficients and used to compute the atomic scattering factor of iodine according to Eq. (22). The parameter in this formula is equal to 4.0712 (see Ref. 27).
Article metrics loading...
Full text loading...