Figure 1

The sketch of the anticlockwise rotating (a) circularly and (b) elliptically polarized laser field and the angular-streaking concept in our coordinate system. (c) The highest occupied three orbitals involved in the single and double ionizations of CO molecule in our experiments, where the nuclei O and C lie on the left and right sides, respectively. (d) The potential energy surfaces of ${\mathrm{CO}}^{+}$ and ${\mathrm{CO}}^{2+}$ interested in this work (adapted from Ref. 31). The $X{}^2\sum ^{+}$ or $A{}^2\prod _{}^{}$ state of ${\mathrm{CO}}^{+}$ is populated by removing an electron from HOMO or HOMO-1 of the neutral CO, which transits to the ${}^3\sum ^{+}$ or $X{}^3\prod _{}^{}$ state of ${\mathrm{CO}}^{2+}$ by removing the second electron from HOMO-2 or HOMO, respectively.Reuse & Permissions

Figure 2

(a) The KER dependent molecular-frame angular distribution of the photoelectron emitted from ${\mathrm{C}}^{+}+\mathrm{O}$, and (b) its integrations over different KER ranges. (c) The KER distribution of the single ionization induced dissociation channel of ${\mathrm{C}}^{+}+\mathrm{O}$. The CO molecule is orientated with C points to the positive direction of the y-axis (i.e., ${\Phi }_e=0°$). The ${\Phi }_e=+90°$ corresponds to electron tunneling when the electric field points from C towards O; i.e., the carbon is on the down hill side of the potential. The electrons are then angularly streaked towards ${\Phi }_e=+90°$. The intensity of the anticlockwise rotating circularly polarized pulse is estimated to be $\sim 4.0\times {10}^{14}\mathrm{W}/{\mathrm{cm}}^2$. (d) The predicted angular-dependent ionization rates of CO simulated by using the MO-ADK and SFA as well as their corrections with the Stark effect (adapted from Ref. 24), which are normalized and compared with our experimental data (the measured angular distribution is rotated by $-90°$ to take into account the angular-streaking effect).Reuse & Permissions

Figure 3

(a) The KER distribution of the exploded double ionization channel of ${\mathrm{C}}^{+}+{\mathrm{O}}^{+}$. (b)–(d) The KER dependent ion sum-momentum distributions of the ${\mathrm{C}}^{+}+{\mathrm{O}}^{+}$ channel along the minor polarization axis ($z$ axis, ${\mathrm{pz}}_{\mathrm{sum}}$) of the elliptically polarized pulse. The condition of the ${\mathrm{C}}^{+}$ emits to the positive (${\mathrm{py}}_{{\mathrm{C}}^{+}}>0$) or negative (${\mathrm{py}}_{{\mathrm{C}}^{+}}<0$) direction of the $y$ axis is applied in (c) and (d), respectively. The corresponding ion sum-momentum distributions integrated over different KER ranges are plotted in (e)–(g). The solid curves show the fits of the measured three-peak structures by considering the convolution of two sequentially emitted electrons according to the function of ${\mathrm{pz}}_{\mathrm{sum}12}$ (see text). Only the molecules orientated within a cone of 45° around the major polarization axis ($y$ axis) are selected. The intensity of the anticlockwise rotating elliptically polarized pulse with an ellipticity of $\epsilon \sim 0.7$ is estimated to be $\sim 2\times {10}^{15}\mathrm{W}/{\mathrm{cm}}^2$.Reuse & Permissions