Vibrationally resolved electron-nuclear energy sharing in above-threshold multiphoton dissociation of CO

We study the photon energy sharing between the photoelectron and the nuclei in the process of above-threshold multiphoton dissociative ionization of CO molecules by measuring the joint energy spectra. The experimental observation shows that the electron-nuclear energy sharing strongly depends on the vibrational state. The experimental observation shows that both the energy deposited to the nuclei of $\mathrm{C}{\mathrm{O}}^{+}$ and the emitted photoelectron decrease with increasing the vibrational level. Through studying the vibrationally resolved nuclear kinetic energy release and photoelectron energy spectra at different laser intensities, for each vibrational level of $\mathrm{C}{\mathrm{O}}^{+}$, the nuclei always tend to take the same amount of energy in every vibrational level regardless of the laser intensity, while the energy deposited to the photoelectron varies with respect to the laser intensity because of the ponderomotive shifted energy and the distinct dissociative ionization mechanisms.

Figure 1

(a) Electron-nuclear JES of above-threshold multiphoton dissociative ionization channel of CO(1,0) at an intensity of $0.6\times {10}^{14}\mathrm{W}/\mathrm{c}{\mathrm{m}}^2$. (b) and (c) show the corresponding photoelectron energy spectrum and the nuclear KER spectrum, respectively.

Figure 2

(a) The angular distribution of the dissociative fragment ${\mathrm{C}}^{+}$ at an intensity of $0.6\times {10}^{14}\mathrm{W}/\mathrm{c}{\mathrm{m}}^2$. Here θ is the angle between the molecular axis and the direction of the laser polarization. (b) The ratio of both parallel and perpendicular transitions with respect to $\left|\cos \theta \right|$ at different laser intensities.

Figure 3

(a) The potential energy curves of $\mathrm{C}{\mathrm{O}}^{+}$ (taken from [33]). The two possible initial electronic states involved in this experiment, $X{}^2{\sum }^{+}$ and $A{}^2\prod$, are labeled with the short lines referring to the vibrational levels. (b) Dressed-state diabatic states of $\mathrm{C}{\mathrm{O}}^{+}$. Lines with different color refer to different transition pathways contributing to vibrationally resolved KER (see text).

Figure 4

(a) The energy deposited to the nuclei of $\mathrm{C}{\mathrm{O}}^{+}\left({E_N}_0\right)$ with respect to the photoelectrons $E_e$ in different vibrational levels. (b) Frank-Condon factors ($\mathrm{CO}X{}^1{\sum }^{+},{\upsilon }^{\prime }=0\to \mathrm{C}{\mathrm{O}}^{+}X{}^2{\sum }^{+},{\upsilon }^{″}=0-7$ as a function of vibrational energy $E_{{\upsilon }^{″}}$).

Figure 5

The energy deposited to (a) the nuclei of $\mathrm{C}{\mathrm{O}}^{+}\left({E_N}_0\right)$ and (b) the emitted photoelectron $\left(E_e\right)$ in different vibrational levels at different laser intensities.