Metastable Autoionizing States of Molecules and Radicals in Highly Energetic Environment
Abstract
This proposal focuses on the electronic structure method development targeting electronic states that are metastable with respect to electron detachment and computational studies of fundamental chemical processes involving molecules and radicals in highly excited states. Such metastable electronic states, which lie above the ionization (or electron-detachment) continuum, are called resonances; they are common in energetic environments such as plasma, which is generated in electric arcs, supersonic combustion, fusion reactors, plasma displays, extremely hot flames, lightning, polar aurorae, etc. Plasmas (and, consequently, these metastable states) play an important role in technology. Moreover, the quantum mechanical description of resonances is of fundamental importance on its ownÑit is a prerequisite for understanding chemical dynamics in plasmas and matter in high-energy environments. We are developing new methodology based on complex-variable approaches such as complex-scaled (CS) hamiltonians and complex-absorbing potential (CAP) techniques that allow one to extend quantum chemical methods devised for bound states to resonances. We developed efficient codes for CS and CAP EOM-CCSD and introduced important improvements into the formalism, such as a new approach for deperturbing the energy by removing the CAP contributions, which greatly improved their robustness and predic- tive power, especially in applications to molecules. For example, our deperturbed CAP-EOM-CCSD method yields smooth and internally consistent potential energy surfaces for transient anions (this has not been achieved in prior applications of the CAP technique). In the scope of this proposal, we pursue the following directions: (i) extension to core-ionized states via new iterative diagonalization approaches; (ii) improvement of computational efficiency and extending these tools for larger molecules via resolution-of-identity (RI) and Cholesky decomposition (CD) techniques as well as parallelization; (iii) development of the formalism and codes for calculations of properties (such as transition dipole moments and Dyson orbitals) and integration with our code for calculating photoionization/photodetachment cross sections; and (iv) development of the conceptual framework for the analysis of complex densities and density currents. These developments will enable fundamental studies of processes involving metastable species and will aid practical applications (such as facilitating the interpretation of novel experiments using new advanced light sources). For example, core-ionized states are encountered in experiments using high-energy X-ray (e.g., near-edge absorption) or novel free-electron lasers. The ability to compute dipole moments and Dyson orbitals is a prerequisite for calculating photoionization/photodetachment cross sections, which is important for planning and interpreting a broad range of experiments. The positions, oscillator strengths, and lifetimes of resonance states are necessary for kinetic modeling of processes in highly energetic environments, such as supersonic combustion, extremely hot flames, fusion reactors, and explosives, as well as for interpreting experimental studies involving high-energy ionization (e.g., for modeling photoionization efficiency curves). Thus, we anticipate that our codes will be used by a broad range of scientists and engineers. The proposed program goes beyond developing practical tools for studying and quantifying properties of metastable states, such as directions (i)-(iii) above. We also aim to develop a new conceptual framework for resonances [direction (iv)]. We intend to explore new ways of analyzing imaginary density, with the goal of deriving insight about decay channels and revealing connections between the molecular structure and electronic properties of resonances. Method development will be conducted in parallel with validation and benchmarking, and collaborations with experimentalists.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Feb 19, 2019
- Source ID
- W911NF1610232
Entities
People
- Anna Krylov
Organizations
- Army Contracting Command
- United States Army
- University of Southern California