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首页> 外文期刊>The Journal of Chemical Physics >Photodissociation of acetone from 266 to 312 nm: Dynamics of CH3 + CH3CO channels on the S-0 and T-1 states
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Photodissociation of acetone from 266 to 312 nm: Dynamics of CH3 + CH3CO channels on the S-0 and T-1 states

机译：从266到312 nm的丙酮的光解离：S-0和T-1状态下CH3 + CH3CO通道的动态

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摘要

The photodissociation dynamics of acetone (CH3)(2)CO, cooled in a molecular beam, have been explored over the wavelength range 266-312 nm. Nascent CH3 fragments were detected by resonance-enhanced multiphoton ionization, followed by mass-selected ion imaging. For photolysis at lambda = 306 nm, the image shows a sharp ring, which, when converted to a translational energy distribution, reveals a narrow Gaussian peak with a maximum at 90% of the available energy. As the photolysis energy is increased, the distribution slowly broadens and shifts to higher recoil translational energy. The fraction of available energy in translation energy decreases in favour of internal energy of the CH3CO fragment. These observations are consistent with a dynamical model in which the energy of the exit channel barrier on the T-1 surface evolves mostly into relative translational energy. Energy in excess of the barrier is partitioned statistically into all degrees of freedom. No evidence was found for any other dynamical pathway producing CH3 fragments, including reaction on S-0 or S-1, for dissociation between 306 and 266 nm. For lambda > 306 nm, a diffuse, slow recoil component to the image appears. The translational energy distribution for this component is fit well by a statistical prior distribution of energy. We attribute this component to dissociation on the S0, ground state surface; to our knowledge, this is the first direct observation of this channel. The appearance of S0 dynamics and the disappearance of the T-1 component are consistent with previously inferred barrier height on T-1 for the production of CH3CO + CH3. The possible atmospheric implications of our findings are discussed. Published by AIP Publishing.
机译：在分子束中冷却的丙酮（CH3）（2）Co的光解离动力学已经在波长范围内探讨了266-312nm。通过共振增强的多相电离检测新生CH3片段，然后进行质量选择的离子成像。为了在Lambda = 306nm处的光解，图像示出了尖锐环，当转换成转换为平移能量分布时，揭示了一个窄的高斯峰，最大为90％的可用能量。随着光解能的增加，分布缓慢拓宽并转向更高的反冲翻译能量。翻译能量中可用能量的分数减少了CH3CO片段的内部能量。这些观察结果与动态模型一致，其中T-1表面上的出口通道屏障的能量主要进入相对平移能量。过量障碍的能量在统计上划分为各种自由度。对于产生CH 3片段的任何其他动态途径没有发现证据，包括S-0或S-1的反应，用于在306和266nm之间解离。对于Lambda> 306nm，出现漫反射，显示图像的慢反冲分量。该组分的平移能量分布通过统计的能量分布良好。我们将此组件归因于在S0上的解离，接地状态表面;据我们所知，这是第一次直接观察该渠道。 S0动力学的外观和T-1组分的消失是与先前推断的T-1上的屏障高度一致，用于生产CH3CO + CH3。讨论了我们的研究结果可能的大气影响。通过AIP发布发布。

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