Giegerich Jens, Fischer Ingo
Institute of Physical and Theoretical Chemistry, University of Würzburg, Am Hubland, D-97074 Würzburg, Germany.
J Chem Phys. 2015 Jan 28;142(4):044304. doi: 10.1063/1.4906605.
The photodisscociation dynamics of the alkyl radicals i-propyl (CH(CH3)2) and t-butyl (C(CH3)3) are investigated by H-atom photofragment imaging. While i-propyl is excited at 250 nm, the photodynamics of t-butyl are explored over a large energy range using excitation wavelengths between 347 nm and 233 nm. The results are compared to those obtained previously for ethyl, CH3CH2, and to those reported for t-butyl using 248 nm excitation. The translational energy (ET) distribution of the H-atom photofragments is bimodal and appears rather similar for all three radicals. The low ET part of the distribution shows an isotropic photofragment angular distribution, while the high ET part is associated with a considerable anisotropy. Thus, for t-butyl, two H-atom loss channels of roughly equal importance have been identified in addition to the CH3-loss channel reported previously. A mechanism for the photodissociation of alkyl radicals is suggested that is based on interactions between Rydberg- and valence states.
通过氢原子光碎片成像研究了异丙基（CH(CH₃)₂）和叔丁基（C(CH₃)₃）烷基自由基的光解离动力学。虽然异丙基在250nm处被激发，但使用347nm至233nm之间的激发波长在较大能量范围内研究了叔丁基的光动力学。将结果与先前获得的乙基（CH₃CH₂）的结果以及使用248nm激发报道的叔丁基的结果进行了比较。氢原子光碎片的平动能（ET）分布是双峰的，并且对于所有三种自由基来说看起来相当相似。分布的低ET部分显示出各向同性的光碎片角分布，而高ET部分与相当大的各向异性有关。因此，对于叔丁基，除了先前报道的CH₃损失通道之外，还确定了两个重要性大致相等的氢原子损失通道。提出了一种基于里德堡态和价态之间相互作用的烷基自由基光解离机制。
