Tags: Physical Seminar


Examining Cyclic Ether Consumption in Low-Temperature Oxidation

Oxiranes are a class of cyclic ethers formed in abundance during low-temperature combustion of hydrocarbons and biofuels. While rate coefficients for the formation of 2,3-dimethyloxirane are reported extensively, subsequent reaction mechanisms of the cyclic ether are not. As a result, chemical kinetics mechanisms commonly adopt simplified chemistry to describe the consumption of 2,3-dimethyloxirane, which may introduce mechanism truncation error…


Extracting Kinetic Data from Reactive Molecular Dynamic Simulations

Reactive molecular dynamics (RMD) is a branch of molecular dynamics in which chemical reactions can be simulated. This is made possible by a special group of force fields (e.g. ReaxFF) which allow for dynamic bond orders to be calculated as a function of bond distance. RMD simulations are particularly useful in situations where experiment would be too difficult or expensive to justify without some indication of success. They can also serve to…


Attosecond Transient Absorption “Spooktroscopy”: Using entanglement to overcome spectral instability in Xray Free Electron Lasers

X-ray Free Electron Lasers (XFELs) produce high intensity X-rays with attosecond pulse durations by “undulating” an electron beam at high speeds. The generation of these X-ray pulses allow for Attosecond Pump-Probe Spectroscopy to be used on dilute, gas phase samples. However, XFELs have a problem with shot to shot spectral variation, and due to this, they are not well suited to absorption measurements. To combat this, researchers at the…


Photochemical Synthesis and Spectroscopy of Polycyclic Aromatic Hydrocarbon Dimers

Laser desorption time-of-flight mass spectrometry (LD-ToF-MS) experiments on pressed-pellet samples of polycyclic aromatic hydrocarbons (PAHs) produce covalently-bonded dimers at masses (m/z) of 2M-2 and 2M-4 (where M is the parent mass). Through replication of these LD-ToF-MS conditions at higher throughput, PAH dimers have been produced and collected in milligram quantities. For collected samples of pyrene, perylene, and coronene,…


Experimental Catalyst Design Aided by Machine Learning

In the past, catalyst design has been highly characterized by trial and error based on previous experience and knowledge of catalysis.1 Due to the number of variables involved in catalyst performance, it is difficult to manually optimize highly active catalysts. In the past few years, there has been a movement toward the use of machine learning as a tool in experimental catalyst design. There have been numerous studies published using different…


Insights Into Molecular Structure Via Atomic Force Microscopy

Accurately characterizing the structure of molecules is a fundamental goal for chemists. Many powerful techniques exist to do so (e.g. NMR, IR Spectroscopy, X-ray Crystallography, etc.) and have proven themselves to be extremely effective. However, there are certain cases where these standard ensemble methods struggle to characterize certain systems. In 1986, Binning and coworkers developed Atomic Force Microscopy (AFM) as a complementary method…


Coupled Cluster Externally Corrected by Adaptive Configuration Interaction

An externally corrected coupled cluster (CC) 1 method, where an adaptive configuration interaction (ACI) 2,3 wave function provides the external cluster amplitudes, named ACI-CC, was presented. By exploiting the connection between configuration interaction and coupled cluster through cluster analysis, the higher-order T3 and T4 terms obtained from ACI are used to augment the T1 and T2 amplitude equations from traditional coupled cluster. These…


Gaseous SO2 and H2O Droplets: A Deep Dive Into Surface-level Interactions

The interactions between gaseous SO2 and the surface of water droplets have been studied extensively over the years due to the environmental impacts of aerosols. Spectroscopic methods including vibrational sum-frequency spectroscopy (VSFS) have been used to better understand the mechanism in which gaseous SO2 reacts and dissolves on a water droplet surface1-3. A weakly bonded SO2:H2O complex on the surface of water droplets has been observed…


Application of Kinetic Doping of Silica Sol-Gel Thin Films to Internal Coating of Capillary Tubes and Doping of Branched Polyethylenimine

Doped or functionalized silica thin films are highly desirable technologies for many chemical applications. Current procedures for doping can be costly, environmentally unfriendly, require many synthetic steps, or have low doping efficiency. Kinetic doping is a technique for loading guest molecules into sol-gel thin films that involves introducing guest molecules into a still-evolving film, allowing them to be entrapped by the growing silica…


Two-dimensional electronic spectroscopy study of the Fenna-Matthews-Olson photosynthetic protein

Excitation of light-harvesting pigment-protein complexes is the first step in photosynthesis. The absorbed energy is transferred to reaction centers where it is used to fuel biological processes. Pump-probe and time-resolved fluorescence spectroscopy have been traditionally used to study the energy flow within these systems. However, in the past decades two-dimensional electronic spectroscopy (2DES) emerged as a powerful technique for detailed…
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