Electron Attachment to van der Waals Molecules

范德华分子上的电子吸附不仅在气相中的基本反应过程中，而且在电离气体中的各种现象中都是非常重要的。最近，我们课题组在气相中获得了一些特殊的电子附着过程，这被解释为与范德沃尔斯分子的附着过程。本项目的目的是阐明范德华分子上电子附着的基本机理，并提取在不同反应动力学中控制这一过程的一般规律。在这项工作中，首先用微波电导技术结合脉冲辐解方法详细地研究了O_2、N_2O、NO、NO_2、SO_2、C_3O_2和一些卤代烷分子上的电子附着。得到了分子吸附过程速率常数的绝对值，阐明了分子吸附过程的机理。此外，还得到了速度常数与压力和温度的关系，其中明显地观察到了电子与范德华分子的结合。为了用更直接的方法扩展上述研究，我们构建了一台由范德华分子在超音速膨胀中产生的低能电子能量损失谱装置。我们已经用常规喷嘴获得了孤立原子和分子的电子能量损失谱和光谱散射角的关系，证实了在超音速喷嘴膨胀过程中有效地产生了范德华分子和范德华团簇。

Electron attachment to van der Waals molecules is of great importance not only in a fundamental reaction process in gas phase but also in various phenomena in ionized gas. Very recently, our group has obtained some peculiar phenomena in electron attachment process in gas phase, which has been interpreted in terms of an attachment process to van der Walls moleules. The objectives of the present project are to elucidate a fundamental mechnizm of the peculiar phenomena in the electron attachment to van der Waals molecules and to extract general rules which governs the process in various reaction kinetics.In this work, first, electron attachment to isolated moleules of O_2, N_2O, NO, NO_2, SO_2, C_3O_2, and some alkyl halides has been studied in detail using a microwave conductivity technique combined with a pulse radiolysis 1method. The absolute values of rate constants of the attachment process to the molecules have been obtained elucidating the mechanizm of the attachment process. Furthermore, pressure dependence and temperature dependence of the rate constants have been obtained, in which electron attachement to van der Waals molecules are clearly observed.In order to extend the study described above by means of a more direct method, we have constracted an apparatus of a low energy electron energy loss spectroscopy from van der Waals molecules produced in a supersonic expansion. We have already obtained electron energy loss spectra and scattering angular dependence of the spectra for isolated atoms and molecules using a convensional effusive nozzle, and confirmed efficient production of van der Waals moleules and van der Waals clusters in supersonic nozzle expansion.