RUI: Exploring Differences between Condensed Phase Photolysis and Radiolysis

在获奖的情况下，化学系的化学结构、动力学和机制(CSDM-A)计划资助韦尔斯利学院的Christopher Arumainayagam教授研究由光和/或电子相互作用驱动的化学反应。Arumainayagam博士设计了探测器，用于研究低能电子或光子照射前后纳米级薄膜在超高真空条件下的成分。这些探测器使他的团队能够观察和描述辐射引起的微妙但重要的化学变化。这一重要的化学反应类别影响到在工业上重要的过程中使用的低温等离子体，如等离子体蚀刻；使用低能电子而不是光子进行高度选择性的键解离；识别与星际合成复杂有机分子(COM)的特定路径相关的示踪分子；以及电子和光子在大气过程中的相对作用。计划让女性和少数族裔本科生参与这项研究，以促进STEM劳动力的多样化。这项工作专门寻求评估由低能(8 EV)电子和光子引发的反应之间的差异和相似之处。靶体系包括凝聚相氨、水和甲醇，分别用辐照后程序升温脱附、辐照后红外反射吸收光谱和等温电子/光子刺激脱附进行了研究。具有亚电离能的电子/光子被用来避免产生低能量的二次电子，从而确保了电子和光子辐照之间的根本区别被探测出来。研究的目标包括：(I)测量电子/光子诱导的反应和脱附的有效截面，并确定所有电子/光子诱导的反应产物；(Ii)研究电子/光子通量、入射电子/光子能量和薄膜厚度对反应截面和产率的依赖关系；以及(Iii)确定辐照后程序升温脱附鉴定的产物是否为新生的辐解产物。这些研究旨在确定电子诱导的凝聚相反应是否产生独特的分子物种；以及电子是否比光子更有效地启动特定的凝聚相反应。

With with award, the Chemical Structure, Dynamics, and Mechanisms (CSDM-A) Program of the Division of Chemistry is funding Professor Christopher Arumainayagam at Wellesley College to study chemical reactions that are driven by interactions with light and/or electrons. Dr. Arumainayagam has devised probes to study the composition of nanoscale thin films under ultrahigh vacuum conditions before and after irradiation by low-energy electrons or photons. These probes enable his team to observe and characterize the subtle but important chemical changes induced by irradiation. This important category of chemical reactions impacts low-temperature plasmas used in industrially important processes such as plasma etching; use of low-energy electrons instead of photons for highly selective bond dissociations; identification of tracer molecules associated with specific pathways for interstellar synthesis of complex organic molecules (COM); and the relative roles of electrons and photons in atmospheric processes. Involvement of women and minority undergraduate students in this research is planned to promote diversification of the STEM workforce. The work specifically seeks to assess the differences and similarities between reactions initiated by low-energy ( 8 eV) electrons and photons. Target systems include condensed-phase ammonia, water and methanol, each of which is investigated using post-irradiation temperature programmed desorption, post-irradiation infrared reflection absorption spectroscopy, and isothermal electron/photon-stimulated desorption. Electrons/photons with sub-ionization energies are used to avoid production of low-energy secondary electrons, thereby ensuring that fundamental differences between electron and photon irradiation are probed. Among the objectives of the research are: (i) to measure the effective cross-section for electron/photon-induced reaction and desorption, and to identify all of the electron/photon-induced reaction products; (ii) to study the dependence of the reaction cross-sections and yields on electron/photon fluence, incident electron/photon energy, and film thickness; and (iii) to determine if the products identified by post-irradiation temperature-programmed desorption are nascent radiolysis products. The studies are designed to establish whether electron-induced condensed phase reactions generate unique molecular species; and whether electrons are more effective than photons for initiating specific condensed phase reactions.