RUI: Characterizing Valence, Temporary, and Non-valence Anions: Computational Methods and Photo-detachment Spectroscopy

With support from the Chemical Theory, Models and Computational Methods program in the Division of Chemistry, Professor Thomas Sommerfeld of Southeastern Louisiana University will model temporary molecular anions. Negatively charged molecular ions that decay by spontaneous electron emission are called temporary anions as they show lifetimes similar to other species.

Temporary anions cannot form stable compounds, but they occur as critical intermediates in many natural and technical processes including plasma etching, atmospheric chemistry, radiation damage to living tissue, and cancer therapy. Modeling temporary anions is far more challenging than modeling of stable molecules. Dr.

Sommerfeld and his group aim to simulate the quantum mechanical equations describing all electrons of the temporary anion including the outgoing electron. Professor Sommerfeld will work to develop reliable, cost-efficient models to compute the lifetime of temporary anions, a critical parameter for more coarse-grained simulations. Moreover, Dr.

Sommerfeld’s group will apply the developed methods to aid with the interpretation of photo-detachment spectra measured by Dr. Chick Jarrold’s group at Indiana University. Since Southeastern is a PUI (predominantly undergraduate institution) located in a rural, low-income region of a traditionally low-income state, and since the research will be conducted with undergraduate group members, the impact on disadvantaged students and their access to the research infrastructure is expected to be significant.

Under this award, Professor Thomas Sommerfeld and his group will combine method development for resonance states with the study of photo-detachment experiments. Dr. Sommerfeld will extend his framework for systematic method comparison from model potentials into the electronic structure world and from L²-methods to projection-operator approaches.

Methods for resonances combine at least five aspects: a continuum approach, an electronic structure method, a valence basis, a diffuse basis, and a data analysis. Owing to the large number of factors entering these calculations, comparisons are challenging, and Dr. Sommerfeld will focus on an unbiased comparison of continuum methods.

For this purpose, Dr. Sommerfeld will implement symmetry-conforming confinement potentials into the open-source Psi4 package. Dr.

Sommerfeld will use the new and traditional methods to aid in the interpretation of photo-detachment spectra by elucidating initial state distributions, identifying short-lived intermediates, and suggesting mechanisms. These studies from the Sommerfeld group have the potential for broad scientific impact; most importantly, the development of a systematic framework for comparing continuum methods and the confinement potential based methods in Psi4 would be beneficial for the research community in the area of temporary anion electronic structure.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.