Tags: Physical Seminar


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

Raman Lasers are an interesting option for Resonance Ion spectroscopy. They rely on a Raman transition which is not limited by bound transition. This work demonstrates Raman lasers ability to be used for high resolution spectroscopy to observe atomic transitions. 


Frequency Combs as the Route to the Spectroscopic Trifecta: High Time Resolution, High Frequency Resolution, and High Sensitivity

Many consequential chemical processes take place on ultrafast timescales, including molecular vibrations and bond breaking. Measurements that follow ultrafast molecular dynamics in real time are changing our understanding of these processes. We are designing new tools to study ultrafast molecular dynamics and quantum mechanics with the sensitivity enough to study the molecules in molecular beams and the spectral resolution sufficient for…


Automatic Differentiation of Explicitly Correlated MP2

For a long time, explicitly correlated (F12) methods have offered a solution to the slow convergence of the one-electron basis set. Although there have been numerous studies in which F12 methods have improved the accuracy of single-point energies, most of these methods have not been extended to gradients and Hessians. One such method is the highly robust explicitly-correlated second-order Moeller-Plesset perturbation theory within the 3C(FIX)…


Potential PFAS Degradation Technique: Exploring Plasma-Mediated Chemistry

PFAS (per- and polyfluoroalkyl substances) have been used in a variety of applications over the past 70 years, ranging from firefighting foam to nonstick cookware. The strong carbon-fluorine bond is what gives these substances their desirable chemical characteristics, but this is also the cause of their greatest drawback. They are known as “forever chemicals,” highly persistent chemicals that do not occur in nature, and many of which have been…


Instrumentation and Precursor Development for Infrared Helium Nanodroplet Isolation Spectroscopy

Helium nanodroplet isolation spectroscopy is a technique useful for studying highly reactive, open shell systems due to its low temperature, fast adiabatic cooling, and minimally perturbative matrix. The technique is particularly good at studying pre-reactive complexes with low activation barriers and small, hydrocarbon systems where rotational resolution is maintained due to the superfluid nature of the droplets. These types of systems are…


Kinetic Monte Carlo Simulations for Heterogeneous Catalysis

Monte Carlo simulations are a broad, popular class of algorithms that solve chemical problems by changing the position of atoms in a molecule by small, random displacements over a period of time.  The kinetic Monte Carlo approach improves on its earlier counterparts by allowing all of the atoms to move dynamically and by grouping these molecular vibrations such that they are treated simultaneously until there is a change in the overall…


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…
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