We present a time-resolved study of the photodissociation dynamics of OCS after UV-photoexcitation at λ = 237 nm. OCS molecules (X¹Σ⁺) were primarily excited to the 1¹A′′ and the 2¹A′ Renner–Teller components of the ¹Σ⁻ and ¹Δ 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 ∼100 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(X¹Σ⁺, J ≫ 0) fragments, which has a timescale of ∼140 fs. Instead, we suggest to assign the observed oscillations to the excitation of vibrational wavepackets in the 2³A′′ or 2¹A′′ states of the molecule that predissociate to form S(³P_J) photoproducts.

中文翻译：

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时间分辨OCS的紫外线引发的光解离动力学

我们提出了一个时间分辨的研究OCS在λ = 237 nm的紫外光激发后的光解离动力学。OCS分子（X ¹ Σ ⁺）的主要激发到1个¹甲''和2 ¹甲'的的伦纳-特勒部件¹ Σ ^-和^1点Δ的状态。通过时延强场电离和通过强790 nm激光脉冲对所得CO ⁺和S ⁺片段的动能成像，观察到了离解为CO和S片段。令人惊讶的是，在S ⁺中观察到了大约100 fs的快速振荡离解的通道。基于波包-动力学模拟配上简单的静电相互作用模型，这些振荡不对应于所述离去CO的已知高度激发的旋转运动（X ¹ Σ ⁺，Ĵ »0）片段，其具有的一个时间刻度〜 140英尺 取而代之，我们建议将观察到的振荡分配给预先解离形成S（³ P _J）光产物的分子的2 ³ A ''或2 ¹ A ''状态的振动波包的激发。