Matthaei Christian T, Mukhopadhyay Deb Pratim, Fischer Ingo
Institute of Physical and Theoretical Chemistry, University of Würzburg, Am Hubland, D-97074 Würzburg, Germany.
J Phys Chem A. 2021 Apr 15;125(14):2816-2825. doi: 10.1021/acs.jpca.0c11236. Epub 2021 Apr 5.
UV photodissociation of benzoyl chloride, Ph-CO-Cl, is associated with the loss of a chlorine atom. Here we excite benzoyl chloride to the S, S, and S excited states at 237, 253, 265, and 279.6 nm and detect the Cl photofragment by [1 + 1'] photoionization using 118.9 nm VUV radiation. The translational energy distribution of the Cl atom is measured by velocity map ion imaging. An isotropic image and a unimodal translational energy distribution are observed at all dissociation wavelengths, and a fraction of 18-20% of the excess energy is released into translation. The results indicate a dissociation that predominately proceeds from the vibrationally hot S ground state, although the observed translational energy release deviates significantly from a prior distribution. However, the impulsive model does also not represent the translational energy release. As a Cl/Cl* branching ratio of 9:1 or more is observed in one-color experiments at 235 nm, we conclude that direct dissociation from excited electronic states contributes only to a minor extent.
苯甲酰氯（Ph-CO-Cl）的紫外光解离与氯原子的损失有关。在此，我们在237、253、265和279.6纳米处将苯甲酰氯激发到S₁、S₂和S₃激发态，并使用118.9纳米的真空紫外辐射通过[1 + 1']光电离检测Cl光碎片。通过速度成像测量Cl原子的平动能分布。在所有解离波长下均观察到各向同性图像和单峰平动能分布，且有18 - 20%的过剩能量释放到平动中。结果表明解离主要从振动激发的S₀基态开始，尽管观察到的平动能释放与先前的分布有显著偏差。然而，脉冲模型也不能代表平动能释放。由于在235纳米的单色实验中观察到Cl/Cl*分支比为9:1或更高，我们得出结论，从激发电子态的直接解离仅起次要作用。
