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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Threshold photoionization of fluorenyl, benzhydryl, diphenylmethylene, and their dimers
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Threshold photoionization of fluorenyl, benzhydryl, diphenylmethylene, and their dimers

机译：芴基，二苯甲基，二苯基亚甲基及其二聚体的阈值光电离

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Two π-conjugated radicals, fluorenyl (C_(13)H_9) and benzhydryl (C_(13)H_(11)), as well as the carbene diphenylmethylene (C_(13)H_(10)) were studied by imaging photoelectron-photoion coincidence spectroscopy using VUV synchrotron radiation. The reactive intermediates were generated by flash pyrolysis from 9-bromofluorene and α-aminodiphenylmethane (adpm), respectively. Adiabatic ionization energies (IE_(ad)) for all three species were extracted. Values of 7.01 ± 0.02 eV for fluorenyl and 6.7 ± 0.1 eV for benzhydryl are reported. For the triplet diphenylmethylene, an IE_(ad) of 6.8 ± 0.1 eV is found. The dissociative photoionization of 9-bromofluorene, the precursor for fluorenyl, was also studied and modeled with an SSACM approach, yielding an appearance energy AE_(0K)(C _(13)H_9 +/C_(13)H_9Br) of 9.4 eV. All experimental values are in very good agreement with computations. For fluorenyl, the IE_(ad) agrees well with earlier values, while for the benzhydryl radical, we report a value that is more than 0.6 eV lower than the one previously reported. The geometry change upon ionization is small for all three species. Although individual vibrational bands cannot be resolved, some vibrational transitions in the threshold photoelectron spectrum of fluorenyl are tentatively assigned based on a Franck-Condon simulation. In addition, the dimerization products of fluorenyl and the benzhydryl radical were detected. Ionization energies of (7.69 ± 0.04) and (8.11 ± 0.04) eV were determined for C_(26)H_(18) and C_(26)H_(22), respectively. On the basis of the ionization energies, we identified both molecules to be the direct dimerization products, formed in the pyrolysis without further rearrangement. Both dimers might be expected to play a role in soot formation because the radical monomers do appear in flames.
机译：通过光电子成像研究了两个π共轭基团芴基（C_（13）H_9）和二苯甲基（C_（13）H_（11））以及卡宾二苯基亚甲基（C_（13）H_（10））。使用VUV同步加速器辐射的符合光谱。通过快速热解分别从9-溴芴和α-氨基二苯甲烷（adpm）生成反应性中间体。提取了所有三种物质的绝热电离能（IE_（ad））。据报告，芴基的值为7.01±0.02 eV，二苯甲基的值为6.7±0.1 eV。对于三重联苯二亚甲基，发现IE_（ad）为6.8±0.1 eV。还研究了9-溴芴（芴基的前体）的解离光电离，并使用SSACM方法建模，产生的表观能量AE_（0K）（C _（13）H_9 + / C_（13）H_9Br）为9.4 eV。所有实验值都与计算非常吻合。对于芴基，IE_（ad）与早期值非常吻合，而对于二苯甲基，我们报告的值比先前报告的值低0.6 eV以上。对于所有三种物质，电离时的几何形状变化均很小。尽管无法解析各个振动带，但基于弗兰克-康登模拟，暂时指定芴基的阈值光电子光谱中的某些振动跃迁。另外，检测到芴基和二苯甲基的二聚产物。对C_（26）H_（18）和C_（26）H_（22）分别确定了（7.69±0.04）和（8.11±0.04）eV的电离能。根据电离能，我们确定这两个分子均为直接二聚产物，它们在热解过程中形成而无需进一步重排。由于自由基单体的确会出现在火焰中，因此可以预期两个二聚体都在烟灰形成中起作用。

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