Tags: Physical Seminar


In-Source High-Resolution Spectroscopy Using an Integrated Tunable Raman Laser

Raman Spectroscopy is a powerful technique that can probe states not visible in absorption spectroscopy. One limitation for the resolution of a stimulated Raman scattering experiment is the linewidth of the stokes pump. This proposed method uses a diamond based Fabry-Perot Cavity to generate a narrow linewidth stokes pump leading to increased resolution. Then this laser is used to perform spectroscopy in an Ion-Trap to observe sub-doppler…


Advancements in X-Ray Spectroscopy of Biologically Relevant Transition Metal Catalysts using X-Ray Free Electron Lasers

First row transition metals are at the center of many biological catalysts due to their abundance in nature and ability to accept and donate electrons with relative ease. Determining the electronic and structural changes as a catalytic process proceeds is difficult due to challenges associated with in situ and operando studies. X-Ray spectroscopic methods are powerful tools to elucidate oxidation states, spin states, and nature of the…


Creating Optimal Coordinates for Drastic Cost Reductions in Rigorous Ab Initio Quantum Chemistry Computations

The accurate determination of molecular vibrations and zero-point vibrational energies (ZPVEs) has been a crucial facet of quantum chemistry for decades. As system size increases, computing these molecular properties rapidly approaches computational intractability for ab initio methods such as CCSD(T). The Concordant Mode Approach (CMA) was recently established as a highly accurate protocol for computing vibrational frequencies at a fraction of…


The 37th Annual Charles A. Coulson Lecture: Reactions and Interactions in Complex Chemical Systems

Systems of chemical reactions are central to a wide range of technological and environmental questions, such as autoignition in combustion engines, heterogeneous catalysis, or formation of atmospheric aerosols. Understanding the details of these systems requires knowledge of not only the individual reaction steps but also the way these steps interact in the web of chemical transformations.  At the Combustion Research Facility (CRF) at…


Disagreement on the Degradation Mechanism and Applicability of Kinetic Models for Non-Platinum Group Metal Catalysts in Polymer Electrolyte Membrane Fuel Cells

One large roadblock to the development of commercially viable hydrogen fuel cells is the cost of the platinum group metal (PGM) oxygen reduction reaction (ORR) catalysts used in proton-exchange membrane fuel cells (PEMFCs). Unfortunately, similarly active catalysts, like Fe-N-C catalysts, have suffered from stability issues limiting their use. To better understand these stability issues and design better catalysts a number of degradation…


Competition between Solvent···Solvent and Solvent···Solute Interactions in the Microhydration of the Tetrafluoroborate Anion, BF4–(H2O)n=1,2,3,4

This study systematically examines the interactions of the tetrafluoroborate anion (BF4–) with up to four water molecules (BF4–(H2O)n=1,2,3,4). Full geometry optimizations and subsequent harmonic vibrational frequency computations are performed using a variety of density functional theory (DFT) methods (B3LYP, B3LYP-D3BJ, and M06-2X) and the MP2 ab initio method with a triple-ζ correlation consistent basis set augmented with diffuse functions on…


Nitrogen Vacancy Centers as Quantum Sensors

There has been a growing interest in nitrogen-vacancy (NV) centers as high precision sensors in biology, chemistry, and physics. NV centers are naturally occurring defects in diamonds. They can detect nanoscale perturbations in local temperature, pressure, magnetic and electric fields. These quantum sensors perform optimally in ambient conditions, and their biocompatibility permits their use in vivo. The electronic states of the NV center can be…


Low Temperature Combustion of C5 Cyclic Molecules

Probing reaction mechanisms during low-temperature combustion of cyclopentane, which is a representative naphthene species, is necessary for building a broader understanding of the effect of functional groups present in C5 cyclic biofuels, such as cyclopentanol and cyclopentanone. At temperatures below 1000 K, competing reactions of naphthenes include ring-opening of initial radicals (Ṙ) and oxidation of Ṙ via reaction with O2 that yields…


Semiconductor Quantum Dots: Theory, Production, and Application

Semiconductor quantum dots are quantum confined systems that exist on the nanometer scale. A close examination into the properties of these zero-dimensional dots offers insight into their highly tunable chemistry and optics. This high tunability, in turn, promotes their use in a wide variety of interdisciplinary fields such as photovoltaics and bioimaging. Since the discovery of quantum dots, around 40 years ago, they have been the spark of much…


Construction of a Cavity-Enhanced Transient Absorption Spectrometer for Ultrafast Molecular Beam Measurements

Ultrafast spectroscopy is a powerful tool in order to probe transient dynamics of a variety of chemically relevant systems. Traditional ultrafast spectroscopy is done in either a thin film or solution phase as the concentration of the samples can easily yield high signals at relatively low powers, however these measurements are subject to solvation effects and can have a difficult time agreeing with theoretical models and other experimental…
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