NSF Award
1465161
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. <br/><br/>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.
