二乙基锌的同步辐射真空紫外光电离光解离

Synchrotron Radiation Vacuum Ultraviolet Photoionization and Photodissociation of Diethylzinc

利用同步辐射光源和反射式飞行时间质谱,在超声冷却条件下对二乙基锌(ZnC4H10)进行真空紫外(VUV,能量范围为8-22eV)光电离光解离研究.实验获得ZnC4H10的光电离质谱图;通过测量各碎片离子的光电离效率(PIE)曲线,获得ZnC4H10的电离势(IP=8.20±0.05eV)及其碎片离子(ZnC2H5+、ZnH+、Zn+、C2H5+、C2H3+等)的出现势.根据实验结果,并结合相关文献所给的热力学数据,推导出这些主要碎片离子的生成焓,并分析它们可能的解离通道和主要离子的分支比.结果表明,其主要解离通道是母体离子发生Zn—C键的断裂形成ZnC2H5+和C2H5+离子,ZnC2H5+离子再进一步解离形成Zn+离子,并且含锌碎片离子的丰度占75%以上.

Photoionization and photodissociation of diethylzinc （ZnC4H10） were performed using vacuum ultraviolet （VUV） synchrotron radiation and a time-of-flight mass spectrometer （TOF-MS）. The photoionization mass spectra of all the observed ions from diethylzinc and their photoionization efficiency （PIE） curves with the photon energy from 8 to 22 eV were measured. From their PIE curves, the ionization potential （IP） of ZnC4H10 （IP=8.20±0.05 eV） and appearance potentials of fragment ions （ZnC2H5^＋, ZnH^＋, Zn^＋, C2H5^＋, C2H3^＋, etc.） were obtained. According to the gas phase energetic data from references, the formation enthalpies of chief ions were evaluated and their possible channels of dissociative photoionization as well as their branch rates were discussed. The results indicated that the chief channels were the simple cleavage of Zn-C bond in the parent ions to form fragmental ions C2H5^＋ and ZnC2H5^＋ which further dissociated to Zn^＋ ion. More than 75% of the total production ions belonged to Zn-containing ions.