Department of Chemistry, University of California, Berkeley, California 94720, USA and Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
J Chem Phys. 2017 Oct 7;147(13):134304. doi: 10.1063/1.4994713.
The photodissociation dynamics of the tert-butyl peroxy (t-BuOO) radical are studied by fast-radical-beam coincidence translational spectroscopy. The neutral t-BuOO radical is formed by photodetachment of the corresponding t-BuOO anion at 700 nm (1.77 eV), followed by dissociation at 248 nm (5.00 eV). Photofragment mass and translational energy distributions are obtained. The major channel is found to be three-body fragmentation to form O, CH, and acetone (83%), with minor two-body fragmentation channels leading to the formation of O + tert-butyl radical (10%) and HO + isobutene (7%). Experimental results show that the translational energy distribution for two-body dissociation peaks is close to zero translational energy, with an isotropic angular distribution of fragments. These results indicate that two-body fragmentation proceeds via internal conversion to the ground electronic state followed by statistical dissociation. For three-body dissociation, the translational energy distribution peaks closer to the maximal allowed translational energy and shows an anisotropic distribution of the plane of the dissociating fragments, implying rapid dissociation on an excited-state surface. A small shoulder in the three-body translational energy distribution suggests that some three-fragment dissociation events proceed by a different mechanism, involving internal conversion to the ground electronic state followed by sequential dissociation.
叔丁过氧（t-BuOO）自由基的光离解动力学通过快速自由基束符合平移谱学研究。中性 t-BuOO 自由基是通过在 700nm（1.77eV）处光解相应的 t-BuOO 阴离子形成的，随后在 248nm（5.00eV）处解离。获得了光碎片的质量和平移能分布。主要通道被发现是三体碎裂形成 O、CH 和丙酮（83%），而较小的二体碎裂通道导致 O+叔丁基自由基（10%）和 HO+异丁烯（7%）的形成。实验结果表明，二体解离峰的平移能分布接近零平移能，碎片具有各向同性的角分布。这些结果表明，二体碎裂通过内部转化到基态电子态然后进行统计解离进行。对于三体解离，平移能分布峰更接近最大允许平移能，并显示出解离碎片平面的各向异性分布，这意味着在激发态表面上快速解离。在三体平移能分布中有一个小的肩峰表明，一些三体解离事件通过不同的机制进行，涉及内部转化到基态电子态然后进行顺序解离。
