RUI: Condensed Phase Radiolysis vs. Photolysis

Wellesley College, Wellesley Hills MA

Investigators

Abstract

With this award, the Chemical Structure, Dynamics, and Mechanisms A (CSDM-A) program of the Division of Chemistry is funding Professor Christopher Arumainayagam of Wellesley College to study the differences and similarities between condensed-phase (as opposed to gas-phase) chemical reactions driven by low-energy electrons and light (photons). The main goal is to provide detailed chemical explanations (at the level of the mechanisms of molecular interactions) for macroscopic effects such as how photon- and electron-induced ice chemistry contribute to the (1) ozone hole over the Antarctic and (2) formation of prebiotic (precursors to life) molecules such as glycine in outer space. As well as providing insight into the energetic processing of ices in nature, Professor Arumainayagam’s studies may help to better control industrial chemical reactions to form specific products without unwanted side products. For example, both photons and electrons play a critical role in extreme ultraviolet lithography (EUVL), which is a next-generation manufacturing technique of semiconductor chips critical for better smartphones. In addition to scientific broader impacts to knowledge of ice chemistry, atmospheric chemistry, astrobiology, and industrial chemistry, this Research at Undergraduate Institutions award has a significant impact on education of female undergraduate students, including promoting participation by minority and economically disadvantaged students, and the award includes plans to further promote diversity within the STEM workforce. Students participating in research under this award gain experience with advanced experimental techniques, in addition to skills such as critical thinking, troubleshooting, and problem solving in the research lab. Radiolysis and photolysis of condensed phase NH3, H2O, and CH3OH are being investigated under ultrahigh vacuum (UHV) conditions by using post-irradiation temperature-programmed desorption (TPD), post-irradiation infrared spectroscopy, and isothermal electron/photon-stimulated desorption (ESD/PSD) techniques. Electrons/photons with sub-ionization energies (<10 eV) are employed to avoid the production of cations and low-energy secondary electrons, ensuring that fundamental differences between electrons and photons can be probed. The experiments involve a recently-commercialized high-intensity laser-driven low-energy (<7.4 eV) broadband photon source. When coupled to a monochromator, purchased with funds from this award, this high-intensity photon source will allow for wavelength-dependent condensed phase photochemistry studies that have previously been done at synchrotron facilities. Studying condensed-phase radiolysis and photolysis in a single UHV chamber using the same experimental protocol is critical in exploring fundamental differences between the dynamics of condensed phase electron- and photon-induced reactions. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.