Fully differential study on dissociative ionization dynamics of deuteron molecules in strong elliptical laser fields

Deuteron momentum distributions from the dissociative ionization of ${\mathrm{D}}_2$ in intense elliptically polarized laser fields have been explored in a joint experimental and numerical study. The asymmetrical charge localization in the dissociative ${{\mathrm{D}}_2}^{+}$ offers a large torque, and thus an elliptically polarized laser field efficiently rotates the molecular ion during its dissociation, resulting in the emission of deuterons finally deviating from the bond direction at the instant of tunneling ionization of ${\mathrm{D}}_2$. The rotating torque of the molecular ions increases with the field ellipticity, leading to an ellipticity-dependent tilt angle for the deuteron momentum distribution. Due to the notable rotation of ${{\mathrm{D}}_2}^{+}$ during its dissociation, the photoelectron angular distributions in the laboratory frame and the molecular frame are distinct, which illustrates that the axial recoil approximation is broken for discussing the photoelectron angular distributions of molecules in elliptically polarized laser fields.

Figure 1

The measured deuteron momentum distributions with respect to the field ellipticity at the intensity of $\sim 2.2\times {10}^{14}\mathrm{W}/\mathrm{c}{\mathrm{m}}^2$. The inner circle corresponds to one-photon dissociation and the outer circle corresponds to the net-two-photon dissociation, as marked in (b). The color scale is normalized by their own maxima in each panel.

Figure 2

The simulated deuteron momentum distributions with respect to the field ellipticity at the intensity of $2.2\times {10}^{14}\mathrm{W}/\mathrm{c}{\mathrm{m}}^2$. The color scale is normalized by their own maxima in each panel.

Figure 3

(a) The measured and calculated tilt angles of the deuteron momentum distribution with respect to the ellipticity. (b) The angular momentum of the deuteron with respect to the field ellipticity.

Figure 4

Asymmetrical electron localization when the laser pulse is off for the laser ellipticity $\sim 0.3$ (a) and 0.8 (b). The asymmetry parameter is defined as in [15]. In this simulation, the initial molecular axis is along $z$ axis.

Figure 5

(a),(b) The measured laboratory frame photoelectron momentum distributions at the ellipticity of $\sim 0.3$ and 0.8, respectively. (c),(d) The measured MFPADs at the ellipticity of $\sim 0.3$ and 0.8, where the molecular axis is determined by the asymptotic deuteron emission direction. (e),(f) The measured MFPADs, where the rotation of ${{\mathrm{D}}_2}^{+}$ during its dissociation is deducted at the laser ellipticity of 0.3 and 0.8, respectively.