The fragmentation dynamics of dicationic dimers of acetylene molecules initiated upon strong-field laser ionization is studied. Time-resolved pump-probe experiments with femtosecond laser pulses, accompanied by ab initio dynamical calculations, allow us to evaluate the detailed behavior of molecular ions during the dissociation process. The dynamical properties of the intermediate ${\mathrm{C}}_2{\mathrm{H}}_2^{+}\cdots {\mathrm{C}}_2{\mathrm{H}}_2^{+}$ state created by the pump pulse are probed by a second pulse which causes further ionization. The time-dependent yield of a coincident ${\mathrm{C}}_2{\mathrm{H}}_2^{+}$ $+$ ${\mathrm{C}}_2{\mathrm{H}}_2{}^{2+}$ ion pair exhibits an oscillation feature with a periodicity of 240 $\pm$ 30 fs. Our studies demonstrate that this is caused by an ultrafast rotation of ${\mathrm{C}}_2{\mathrm{H}}_2^{+}$ cations driven by intermolecular Coulomb force together with the orientation-dependent ionization rate. We suggest that the present observation of ultrafast molecular rotation can be a general phenomenon occurring in a wide variety of systems.

中文翻译：

---

弱结合二聚体中超快分子旋转的实时观察

研究了由强场激光电离引发的乙炔分子双官能二聚体的断裂动力学。飞秒激光脉冲的时间分辨泵浦探针实验以及从头算动力学计算，使我们能够评估解离过程中分子离子的详细行为。中间体的动力学性质${\mathrm{C}}_{\mathrm{2个}}{\mathrm{H}}_{\mathrm{2个}}^{+}\cdots {\mathrm{C}}_{\mathrm{2个}}{\mathrm{H}}_{\mathrm{2个}}^{+}$由泵浦脉冲产生的状态被第二个脉冲探测，该第二个脉冲进一步电离。巧合的时间依赖性收益${\mathrm{C}}_{\mathrm{2个}}{\mathrm{H}}_{\mathrm{2个}}^{+}$ $+$ ${\mathrm{C}}_{\mathrm{2个}}{\mathrm{H}}_{\mathrm{2个}}{}^{\mathrm{2个}+}$ 离子对表现出周期性为240的振荡特征 $\pm$30英尺 我们的研究表明，这是由于${\mathrm{C}}_{\mathrm{2个}}{\mathrm{H}}_{\mathrm{2个}}^{+}$分子间库仑力驱动的阳离子以及与方向有关的电离速率。我们建议，目前对超快分子旋转的观察可能是在各种各样的系统中发生的普遍现象。