Stanford PULSE Institute, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA.
J Chem Phys. 2017 Sep 28;147(12):124308. doi: 10.1063/1.4997253.
We have studied strong-field enhanced dissociative ionization of DO in 40 fs, 800 nm laser pulses with focused intensities of <1-3 × 10W/cm by resolving the charged fragment momenta with respect to the laser polarization. We that observe dication dissociation into OD/D dominates when the polarization is out of the plane of the molecule, whereas trication dissociation into O/D/D is strongly dominant when the polarization is aligned along the D-D axis. Dication dissociation into O/D/D and O/D is not seen nor is there any significant fragmentation into multiple ions when the laser is polarized along the C symmetry axis of the molecule. Even below the saturation intensity for OD/D, the O/D/D channel has higher yield. By analyzing how the laser field is oriented within the molecular frame for both channels, we show that enhanced ionization is driving the triply charged three body breakup but is not active for the doubly charged two body breakup. We conclude that laser-induced distortion of the molecular potential suppresses multiple ionization along the C axis but enhances ionization along the D-D direction.
我们研究了 DO 在 40fs、800nm 激光脉冲中的强场增强离解，激光强度聚焦达到<1-3×10W/cm，通过相对于激光偏振方向分辨出带电碎片的动量。我们发现当偏振方向不在分子平面内时，二价离子解离为 OD/D 占主导地位，而当偏振方向沿 D-D 轴对齐时，三价离子解离为 O/D/D 则强烈占主导地位。当激光沿分子的 C 对称轴偏振时，我们既没有观察到二价离子解离为 O/D/D 和 O/D，也没有观察到任何显著的多离子碎裂。即使在 OD/D 的饱和强度以下，O/D/D 通道的产率也更高。通过分析两个通道中激光场在分子框架内的取向，我们表明增强的电离驱动了三重态的三体断裂，但对于二价离子的二体断裂则不活跃。我们得出结论，激光诱导的分子势能的变形抑制了沿 C 轴的多电离，但增强了沿 D-D 方向的电离。
