Creation of multihole molecular wave packets via strong-field ionization

We demonstrate the creation of vibrational wave packets on multiple electronic states of a molecule via strong-field ionization. Furthermore, we show that the relative contribution of the different electronic states depends on the shape of the laser pulse which launches the wave packets.

Figure 1

The four lowest-lying ionic potentials of CH${}_2$I${}_2{}^{+}$. The energy is relative to the neutral ground-state minimum. The numbers in brackets give the vibrational frequency near vertical ionization (FC${}_{\mathrm{pump}}$). The right dotted vertical line indicates the position of the minimum of the neutral ground state (FC${}_{\mathrm{pump}}$). The left dotted vertical line shows the position of the one-photon resonance between $V_1$ and $V_4$ (FC${}_{\mathrm{probe}})$. $V_5$ and higher PESs are separated by at least another $~$2.1 eV from $V_4$ (at $u_B=0$) and not shown in the figure.

Figure 2

Comparison of the CH${}_2$I${}_2{}^{+}$ ion yield vs pump-probe delay for unshaped UV and IR pump pulses. The inset shows the normalized value of the Fourier transform of the data versus frequency in ${\mathrm{cm}}^{-1}$. The vertical lines are placed at 96, 113, and $130\hspace{0.5em}{\mathrm{cm}}^{-1}$. The IR pump data shown here shows peaks at 96 and $113\hspace{0.5em}{\mathrm{cm}}^{-1}$, while data for different IR pulse shapes also show a peak at $130\hspace{0.5em}{\mathrm{cm}}^{-1}$ (see Fig. 3).

Figure 3

Fourier transform of the CH${}_2$I${}_2{}^{+}$ yield in a series IR pump-IR probe scans for various pump pulse chirps (given in fs${}^2$). Each curve is normalized to the peak at $113\hspace{0.5em}{\mathrm{cm}}^{-1}$. The frequencies 96, 113, and $130\hspace{0.5em}{\mathrm{cm}}^{-1}$ are marked by dashed vertical lines. The inset shows the amplitude of the peaks at 96 and $130\hspace{0.5em}{\mathrm{cm}}^{-1}$ (both normalized to the $113\hspace{0.5em}{\mathrm{cm}}^{-1}$ amplitude) vs chirp (in fs${}^2$).