OCS紫外光引发光解动力学的时间分辨
Time-resolving the UV-initiated photodissociation dynamics of OCS
摘要：
我们提出了一个时间分辨的研究后，在$λ=237$ nm的紫外光激发的OCS的光解动力学。OCS分子（$X\,^1Σ^+$）主要被激发至$^1Σ^{-}$和$^1\!Δ$状态的$1\,^1\!A''$和$2\,^1\!A'$ Renner-Teller组分。解离成CO和S片段，观察到通过时间延迟的强场电离和成像的动能产生的CO $^+$和S $^+$片段由强烈的$790$ nm激光脉冲。令人惊讶的是，在紫外解离的S $^+$通道中观察到周期为$\sim100$ fs的快速振荡。基于耦合一个简单的静电相互作用模型的波包动力学模拟，这些振荡不对应于已知的高激发的旋转运动的离开CO $(X\,^1Σ^+,J\gg0)$片段，其具有的时间尺度的$\sim140$ fs。相反，我们建议分配所观察到的振荡的振动波包的激发在$2\,^3\!A''$或$2\,^1\!A''$状态的分子，预解离形成S $(^3\!P_{J})$光产物。
英文摘要：
We present a time-resolved study of the photodissociation dynamics of OCS after UV-photoexcitation at $λ=237$ nm. OCS molecules ($X\,^1Σ^+$) were primarily excited to the $1\,^1\!A''$ and the $2\,^1\!A'$ Renner-Teller components of the $^1Σ^{-}$ and $^1\!Δ$ states. Dissociation into CO and S fragments was observed through time-delayed strong-field ionisation and imaging of the kinetic energy of the resulting CO$^+$ and S$^+$ fragments by intense $790$ nm laser pulses. Surprisingly, fast oscillations with a period of $\sim100$ fs were observed in the S$^+$ channel of the UV dissociation. Based on wavepacket-dynamics simulations coupled with a simple electrostatic-interaction model, these oscillations do not correspond to the known highly-excited rotational motion of the leaving CO$(X\,^1Σ^+,J\gg0)$ fragments, which has a timescale of $\sim140$ fs. Instead, we suggest to assign the observed oscillations to the excitation of vibrational wavepackets in the $2\,^3\!A''$ or $2\,^1\!A''$ states of the molecule that predissociate to form S$(^3\!P_{J})$ photoproducts.
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