New Coupled-cluster Methods for Linear and Non-linear Valence and Core-level Spectroscopy in Gas and Condensed Phase

University Of Southern California, Los Angeles CA

Investigators

Abstract

Anna Krylov of the University of Southern California is supported by an award from the Chemical Theory, Models and Computational Methods program in the Division of Chemistry to develop new theoretical approaches, computer algorithms, and software to describe interaction of molecules and light in new regimes (high energy, high intensities, etc). Using light to interrogate matter is the basis of spectroscopy, which provides the most powerful set of tools for unraveling mechanisms of chemical reactions, structures and intrinsic properties of materials and biological objects. Using high-energy (X-rays) and high-intensity radiation opens new exciting opportunities, which motivate the worldwide development of multi-billion facilities for advanced light sources. Recent advances in beam quality in these facilities greatly expanded possible applications of X-rays, giving rise to a proliferation of techniques including those operating in time-resolved and non-linear regimes. These novel techniques promise to greatly expand our ability to interrogate molecular structure and dynamics, but their full potential can only be realized when experiment is augmented by accurate theoretical tools for modeling these phenomena. Despite significant efforts, the theory is still lagging behind the experimental capabilities, creating a bottleneck for maximizing the scientific impact of multi-billion advanced light source facilities. Krylov will bridge this gap by developing novel electronic structure methods for modeling linear and non-linear core-level spectroscopies in the gas and condensed phases. The research plans include training and mentoring of graduate students and postdocs for careers in academia and industry as well as contributions to the research infrastructure. Capitalizing on her previous work, Krylov will further extend highly reliable coupled-cluster (CC) and equation-of-motion CC (EOM-CC) methods to the domain of core-level ionized and excited states by exploiting core-valence separation (CVS) and damped response theory (or complex polarization propagator, CPP) approaches. Specifically, she will further develop theoretical framework and efficient computer codes for modeling E2PA (entangled 2PA), PECD (photoelectron circular dichroism), MCD (magnetic CD), and electronic SFG (sum-frequency generation) spectra. She aims to develop a uniform theoretical framework for both UV–vis (valence transitions) and X-ray (core-level transitions) domains. Continuing close collaborations with experimentalists guides and calibrate the developments, as well as helps to design new experiments and interpret the experimental results. 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.