中文摘要：

利用同步辐射光电离质谱结合理论计算，研究了异亮氨酸的真空紫外光诱导电离解离．在光子能量为13eV的质谱中探测到了m／z=86、75、74、69、57、46、45、44、41、30、28、18能碎片离子．对于异亮氨酸的主要碎片离子为：C5H12N＋（m／z=86）、C2H5NO4＋（m／z=75）、C5H9＋（m／z=69）、C4H9＋（m／z=57）和CH4N＋确良（m／z=30）．由光电离效率曲线得到出现势分别为：8．84±0．07、9．25±0．06、10．20±0．12、9．25±0．10、11．05±0．07eV．结合量化理论计算（B3LYP／6—31＋＋G（d，p）），详细给出了它们可能的生成路径．这些解离通道包括简单的键断裂反应和涉及中间体、过渡态的反应，实验值和理论计算的离子出现能或势垒一致．关键词：

英文摘要：

Vacuum ultraviolet photon-induced ionization and dissociation of isoleucine are investi- gated with synchrotron radiation photoionization mass spectroscopy and theoretical cal- culations. The main fragment ions at m/z=86, 75, 74, 69, 57, 46, 45, 44, 41, 30, 28, and 18 from isoleucine are observed in the mass spectrum at the photon energy of 13 eV. From the photoionization efficiency curves, appearance energies for the principal fragment ions CsH12N＋ （rn/z=86）, C2H5NO2＋ （m/z=75）, C5H9＋ （rn/z=-69）, C4H9＋ （m/z=57）, and CH4N＋ （m/z=30） are determined to be 8.844-0.07, 9.254-0.06, 10.20-4-0.12, 9.254-0.10, and 11.05＋0.07 eV, respectively, and possible formation pathways are established in detail by the calculations at the B3LYP/6-31＋＋G（d, p） levels. These proposed channels include simple bond cleavage reactions as well as reactions involving intermediates and transition structures. The experimental and computational appearance energies or barriers are in good agreement.