Date of Award
Doctor of Philosophy (PhD)
Johnson, Mark A.
Molecular level interactions give rise to the macroscopic chemical and physical properties of bulk electrolyte systems. A fundamental knowledge of these interactions facilitates understanding of this behavior and enables rational manipulation of the system at the molecular level. Among the experimental techniques, vibrational spectroscopy is widely used in several variations including linear absorption spectroscopy, ultrafast multidimensional spectroscopy, and interface specific spectroscopy. The advantage of using vibrational spectroscopy to study systems at the molecular level is its sensitivity towards structural information as well as relatively high time resolution. Standard solution phase and surface-sensitive spectroscopies, however, suffer from the drawback that the spectra contain simultaneous contributions from species in many distinct chemical environments, which also undergo thermal fluctuations over time. Gas-phase vibrational spectroscopy of cryogenically (~10 K) cooled, mass-selected clusters represents an alternative, “bottom up” approach for elucidating the underlying chemical physics with a high degree of experimental control over the precise chemical composition and temperature. This dissertation utilizes this technique successfully to elucidate the behavior of nitric acid at the molecular level, using ionic water clusters as model microscopic subsystems. Correlations in the vibrational features associated with hydrogen-bonding interactions of acid with water and distortions in the nitrate scaffold gives insight to acidity of nitric acid, in addition to the effect of ion electric fields. In addition, strong solvatochromic shifts in hydrated nitromethane is analyzed in the context of the solute ion polarizability response and partial charge transfer to the water networks.
Mitra, Sayoni, "Spectroscopic Characterization of Microhydration: Studying Molecular Properties, Acidity and Solvation in Ionic Water Clusters using Cryogenic Infrared Vibrational Predissociation Spectroscopy" (2022). Yale Graduate School of Arts and Sciences Dissertations. 635.