Unveiling reaction mechanisms by isomer‐selective detection of reactive intermediates requires advanced spectroscopic knowledge. We study the photoionization of fulvenone (c‐C₅H₄=C=O), a reactive ketene species relevant in catalytic pyrolysis of lignin, which was generated by pyrolysis of 2‐methoxy acetophenone. The high‐resolution threshold photoelectron spectrum (TPES) with vacuum ultraviolet synchrotron radiation revealed well‐resolved vibrational transitions, assigned to ring deformation modes of the cyclopentadiene moiety. The adiabatic ionization energy was determined to be 8.25±0.01 eV and is assigned to the ²A₂← ¹A₁ transition. A broad and featureless band arising at 9 eV is associated with the ²B₁← ¹A₁ excitation. A conical intersection is responsible for the ultrafast relaxation of the fulvenone cation from the into the state resulting in a featureless and lifetime broadened band. These insights will increase the detection capabilities for fulvenone and thereby help to elucidate reaction mechanisms in lignin catalytic pyrolysis.

中文翻译：

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Fulvenone的阈值光电子能谱：木质素平衡中的一种反应性酮衍生物。

通过异构体选择性检测反应性中间体来揭示反应机理需要先进的光谱学知识。我们研究了富烯酮（c-C ₅ H ₄ = C = O）的光电离，这是一种由木质素2-甲氧基苯乙酮的热解产生的木质素催化热解相关的反应性烯酮。具有真空紫外同步加速器辐射的高分辨率阈值光电子能谱（TPES）揭示了分辨良好的振动跃迁，该跃迁被指定为环戊二烯部分的环变形模式。绝热电离能确定为8.25±0.01 eV，并分配给 ² A ₂ ← ¹ A ₁过渡。在9 eV处出现的宽而无特征的频带与 ² B ₁ ← ¹ A ₁激发相关。圆锥形相交导致富烯酮阳离子从 到态的超快弛豫，导致无特征且终生变宽的谱带。这些见解将提高对富维酮的检测能力，从而有助于阐明木质素催化热解中的反应机理。