Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, United Kingdom.
J Chem Phys. 2009 Dec 14;131(22):224305. doi: 10.1063/1.3266940.
Relative partial ionization cross sections and precursor-specific relative partial ionization cross sections for fragment ions formed by electron ionization of methanol have been measured using time-of-flight mass spectrometry coupled with a two-dimensional ion coincidence technique. Relative cross sections are reported for ionizing energies from 30 to 200 eV. Good agreement is found between our data and one set of recently published absolute partial ionization cross sections. Conversely, discrepancies are observed with another set of recently published data; we attribute these discrepancies to the loss of translationally energetic fragment ions. Our precursor-specific cross sections allow the contribution from single and double ionization to the individual fragment ion yields, following ionization of methanol, to be quantified for the first time. Our analysis shows that the contribution of double ionization to the total ion yield reaches a maximum of 20% between 150 and 200 eV.
采用飞行时间质谱联用二维离子符合技术，测量了甲醇在电子电离过程中碎片离子的相对部分离化截面和前体特异性相对部分离化截面。报道了离子化能量在 30 到 200 eV 之间的相对截面。我们的数据与最近公布的一组绝对部分离化截面吻合较好。相反，与另一组最近公布的数据存在差异；我们将这些差异归因于平移能量碎片离子的损失。我们的前体特异性截面首次允许量化甲醇电离后单个和双电离对各个碎片离子产率的贡献。我们的分析表明，在 150 到 200 eV 之间，双电离对总离子产率的贡献达到最大值的 20%。
