Abstract Isopropanol (2-propanol) dissociatively photoionizes primarily into the CH2CHOH+, CH3CHOH+, CH3CHCH3+ fragment ions, and, as a minor product, into (CH3)2COH+ in the 10.0–13.1 eV photon energy range as shown by Imaging Photoelectron Photoion Coincidence (iPEPICO) spectroscopy. At internal energies of below 0.3 eV, the loss of CH4 dominates via a roaming pathway, in which the leaving CH3 abstracts a hydrogen atom from the other methyl group. At higher energies, the kinetically favored direct loss of a methyl radical quickly takes over as its transition state is looser. We use the measured CH3-loss appearance energy of 10.44 ± 0.01 eV to confirm the heat of formation of protonated acetaldehyde, CH3CHOH+, as ΔfH° = 608 ± 1 kJ mol−1 at 0 K. The highest-energy dissociation observed leads to CH3CHCH3+ + OH, which corresponds to C–O bond scission. This process is the premier example of a non-statistical dissociation which can be modeled using a statistical model, albeit with a physically meaningless appearance energy. This channel is shown to be non-statistical due to preferential OH loss from the first electronically excited ion state.

中文翻译：

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漫游或不漫游，这是异丙醇阳离子中甲基的问题

摘要 异丙醇（2-丙醇）主要通过光离光电离成为 CH2CHOH+、CH3CHOH+、CH3CHCH3+ 碎片离子，并且作为次要产物，在 10.0-13.1 eV 光子能量范围内进入 (CH3)2COH+，如成像光电子光电子偶合 (iP ) 光谱学。当内能低于 0.3 eV 时，CH4 的损失主要通过漫游途径，其中离开的 CH3 从另一个甲基中提取一个氢原子。在更高的能量下，甲基自由基的动力学有利的直接损失迅速接管，因为它的过渡态更松散。我们使用测量的 CH3 损失表观能 10.44 ± 0.01 eV 来确认质子化乙醛 CH3CHOH+ 的形成热，因为 ΔfH° = 608 ± 1 kJ mol−1 在 0 K。观察到的最高能量解离导致 CH3CHCH3+ + OH，对应于 C-O 键断裂。这个过程是非统计解离的首要例子，可以使用统计模型建模，尽管具有物理上无意义的外观能量。由于第一电子激发离子态的优先 OH 损失，该通道显示为非统计性的。