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首页> 外文期刊>Journal of mass spectrometry: JMS >Fourier transform infrared matrix-isolation analysis of acetaldehyde fragmentation products after charge exchange with Ar~(?+) under varied ionization density conditions
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Fourier transform infrared matrix-isolation analysis of acetaldehyde fragmentation products after charge exchange with Ar~(?+) under varied ionization density conditions

机译：在不同电离密度条件下与Ar〜（？+）交换电荷后乙醛裂解产物的傅里叶变换红外矩阵分离分析

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摘要

The products of the Ar~(?+) charge exchange ionization of acetaldehyde have been isolated and compared with related photoionization results and computational work. Acetaldehyde has been used to assess the effect of varied ion density in the ionization region of the electron bombardment matrix isolation apparatus. The amount of acetaldehyde destruction has been measured for constant gas-sample composition and constant ionization current for two anode geometries: a pin anode and a plate anode. For the same ionization current, a pin-shaped anode demonstrates higher precursor molecule destruction efficiency (85%) than the plate-shaped anode (30%), resulting in substantial effect on the yield and quantity of isolated products. When the plate anode is used, the observed infrared products correspond to matrix-isolated carbon monoxide (CO), methane (CH_4), ketene (CH_2CO), ethynyloxy radical (HCCO), formyl radical (HCO~?), acetyl radical (CH _3CO~?), vinyl alcohol (H_2C = CH-OH), and cationic proton-bound dimer, Ar_2H~+. When the pin anode is used, the same products are observed with different relative proportions and new absorption features corresponding to dicarbon monoxide (CCO) and methyl radical (CH_3~?) are observed. The surprising observation of infrared absorptions corresponding to vinyl alcohol along with low yield of products anticipated through the analysis of photoelectron-photoionization coincidence measurements suggests that the initially formed fragmentation products are able to further react within the matrix-isolation environment to influence observed product yields. Related experiments, using the isotopomer CD_3CHO, suggest that the observed products are formed via radical-radical reactions that occur under the high pressure conditions of the matrix isolation environment.
机译：已分离出乙醛的Ar〜（α+）电荷交换电离产物，并将其与相关的光电离结果和计算工作进行比较。乙醛已被用于评估电子轰击基质分离装置的电离区域中变化的离子密度的影响。对于恒定的气体样品组成和恒定的电离电流，已针对两种阳极几何形状（销形阳极和板状阳极）测量了乙醛的破坏量。对于相同的电离电流，针形阳极比板形阳极（30％）具有更高的前驱分子破坏效率（85％），从而对分离产物的产量和数量产生实质性影响。当使用板状阳极时，观察到的红外产物对应于基质分离的一氧化碳（CO），甲烷（CH_4），乙烯酮（CH_2CO），乙炔氧基（HCCO），甲酰基（HCO〜α），乙酰基（CH _3CO〜？），乙烯醇（H_2C = CH-OH）和阳离子质子结合的二聚体Ar_2H〜+。当使用针形阳极时，观察到相同产物具有不同的相对比例，并且观察到对应于一氧化碳（CCO）和甲基（CH 3-α）的新吸收特征。令人惊讶的观察到对应于乙烯醇的红外吸收以及通过对光电子-光电离重合测量的分析预期的低产率的产物表明，最初形成的裂解产物能够在基质分离环境中进一步反应以影响观察到的产物的产率。使用同位素异构体CD_3CHO进行的相关实验表明，观察到的产物是通过在基体分离环境的高压条件下发生的自由基自由基反应形成的。

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