Tags: Physical Seminar


Applications of Material Science in Support of Nuclear Forensics and Non-Proliferation

With globalization and the spreading availability of technologies, nuclear proliferation challenges continue to grow and evolve. Savannah River National Laboratory (SRNL) works to counter proliferation by providing scientific and technological solutions, as well as expert advice to combat emerging threats. Working with the National Nuclear Security Administration (NNSA) and other government agencies, SRNL’s Global Security Directorate provides…


Strategies for the Reduction of Detailed Chemical Kinetics Mechanisms

Detailed chemical kinetics mechanisms describing low-temperature combustion often include thousands of species and reactions due to the abundance of intermediates and their complex potential energy surfaces. While these mechanisms are necessary for accurately predicting species concentrations and global combustion metrics, they are often too large for practical engine simulations that require computational fluid dynamics. As such, strategies…


Photodissociation Spectroscopy of Carbon Cluster Cations


Quantum Computers for Quantum Chemistry: Making the Best of a Limited Technology

Development of error correcting quantum computers for practical computations still lies out of reach. However, many algorithms have been designed for use with near-term quantum computers, commonly referred to as Noisy Intermediate-Scale Quantum (NISQ) devices. On such devices, there is a conflict between increasing computational power while maintaining a short quantum circuit depth. More circuits are needed to simulate more complex systems, but…


Energetics and Kinetics of Various Cyano Radical Hydrogen Abstractions

The cyano radical (CN) is an abundant, open-shell molecule found in a variety of environments, including the atmosphere, the interstellar medium and combustion processes. In these environments, it often reacts with small, closed-shell molecules via hydrogen abstraction. Both carbon and nitrogen atoms of the cyano radical are reactive sites, however the carbon is more reactive with reaction barrier heights generally between 2-15 kcal/mol lower…


Four Isomers of In2H2: a Careful Comparison Between Theory and Experiment

Four constitutional isomers of diindium dihydride have been studied utilising rigorous quantum mechanical methods. Geometries were optimised with the CCSD(T) method using the aug-cc-pwCVTZ basis set and a small-core pseudopotential for the indium atoms. Relative energetics were determined at the CCSD(T)/CBS level of theory, and the higher order δT(Q) contributions are also computed. The monobridged and vinylidene-like isomers lie 10.8 and 13.6…


The Many-Body Expansion in Chemistry

The Many-Body Expansion (MBE) of the energy of a chemical system is a powerful tool that encodes physical descriptors of cooperative effects in chemical systems. Depending on the definition of what a “body” is, the expansion can be applied to a wide variety of chemical ensembles. When applied to hydrogen bonded systems, such as water and aqueous ionic clusters including ions in the Hofmeister series, it has direct implications in the development…


HENDI Spectroscopy of the Butyl Radicals

Butyl radicals (n-, s-, i-, and tert-butyl) are formed from the pyrolysis of nitrite or azo- precursors. The radicals are doped into a beam of liquid helium droplets and probed with infrared action spectroscopy from 2700−3125 cm-1, allowing for a low temperature measurement of the CH stretching region. The presence of anharmonic resonance polyads in the 2800 − 3000 cm-1 region complicates its interpretation. To facilitate spectral assignment,…


Development of Sub-Mechanisms for Cyclic Ethers: Alkyl-Substituted Oxiranes

Oxiranes are a class of cyclic ethers formed in abundance during the low-temperature combustion of hydrocarbons and biofuels from the unimolecular decomposition of hydroperoxyalkyl radicals (Q̇OOH). For example, ethyloxirane, cis-2,3-dimethyloxirane, and trans-2,3-dimethyloxirane are produced as intermediates during the oxidation of n-butane. While rate coefficients for the unimolecular decomposition of Q̇OOH to the aforementioned species are…


A Helium Nanodroplet Instrument for Infrared Spectroscopy of Molecular Ions

Helium nanodroplets provide a cold, inert, and optically transparent environment for doping atomic and molecular species. Helium's weak interaction with dopants is minimally perturbing, and facilitates the collection of high-resolution vibrational and rotational spectra. An instrument was designed that facilitates the ionization of dopant molecules using resonant two-photon ionization. Excitation of the molecular ions then occurs using a tunable…
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