Nonadiabatic dynamics of ethylene in femtosecond laser pulses

The dynamics of the ethylene molecule in femtosecond laser pulses is studied as a function of the laser parameters using an ab initio time-dependent approach, called nonadiabatic quantum molecular dynamics. We predict that, by choosing different femtosecond pulses with well-defined excitation frequencies, one can selectively induce either the isomerization process or different fragmentation phenomena.

Figure 1

Ground state $S_0$ (solid line, without additional markers) and several excited electronic energies of ethylene for different torsion angles $\varphi$ (in degrees) calculated using the TDHF procedure. The lowest excited state depicted (solid line with solid circles) corresponds to the $S_1$ surface.

Figure 2

Multifragmentation with hydrogen separation resulting from laser excitation with a frequency $\omega =13.6\mathrm{eV}$ and an intensity of $2\times {10}^{13}\mathrm{W}∕{\mathrm{cm}}^2$. The time evolution of the torsion angle $\varphi$, the length of the $\mathrm{C}\mathrm{C}$ double bond, $R_{\mathrm{C}\mathrm{C}}$, and the mean $\mathrm{C}\mathrm{H}$ distance $R_{\mathrm{C}\mathrm{H}}$ are presented. The arrow indicates the time of the maximum amplitude of the laser field.

Figure 3

Same as in Fig. 2 but for the $\mathrm{C}\mathrm{C}$ double-bond fission resulting from a laser with a frequency of $9.6\mathrm{eV}$ and an intensity of ${10}^{14}\mathrm{W}∕{\mathrm{cm}}^2$.

Figure 4

Same as in Figs. 2, 3 but for the cis-trans isomerization resulting from a laser with a center frequency of $6.2\mathrm{eV}$ and an intensity of $5\times {10}^{13}\mathrm{W}∕{\mathrm{cm}}^2$.