RUI: Exploring Differences between Condensed Phase Photolysis and Radiolysis

化学系的化学结构，动力学和机制（CSDM-A）计划正在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，用于研究在低能量电子或光子照射前后，纳米级薄膜在真空条件下的成分。 这些探针使他的团队能够观察和表征辐射引起的微妙但重要的化学变化。 这类重要的化学反应影响了在工业上重要的工艺中使用的低温等离子体，例如等离子体蚀刻;使用低能电子而不是光子进行高度选择性的键离解;识别与复杂有机分子（COM）星际合成的特定途径相关的示踪分子;以及电子和光子在大气过程中的相对作用。 计划让女性和少数民族本科生参与这项研究，以促进STEM劳动力的多样化。 这项工作特别试图评估由低能（8 eV）电子和光子引发的反应之间的差异和相似之处。目标系统包括冷凝相氨，水和甲醇，其中每一个都是使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/光子激发脱附研究。具有亚电离能的电子/光子用于避免产生低能二次电子，从而确保探测电子和光子照射之间的根本差异。本研究的主要目的是：（i）测量电子/光子诱导反应和脱附的有效截面，并确定所有的电子/光子诱导反应产物;（ii）研究反应截面和产率对电子/光子注量、入射电子/光子能量和膜厚的依赖关系;和（iii）确定通过辐照后程序升温脱附鉴定的产物是否是新生辐解产物。这些研究旨在确定电子诱导的凝聚相反应是否会产生独特的分子物种;以及电子是否比光子更有效地引发特定的凝聚相反应。

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.