Physical & Analytical Chemistry Seminar: Complex Resonance Eigenvalues from Hermitian (Standard) Quantum Chemistry Packages

Physical & Analytical Chemistry Seminar: Complex Resonance Eigenvalues from Hermitian (Standard) Quantum Chemistry Packages

January 22nd

12:30

Gal Bouskila, under the supervision of Prof. Nimrod Moiseyev

Resonances are perhaps amongst the most pivotal phenomena in nature,
especially in chemistry. Molecules in metastable states (so called resonances)
do not ionize or dissociate immediately despite the fact they have enough energy
for that. Nevertheless, they decay after a finite lifetime. The products of their
decay can be electrons, molecules, ions and radicals.
Non-Hermitian (NH) quantum mechanism (QM) provides powerful numerical
and analytical tools for studying resonance phenomena. However, NHQM
lacks available quantum chemistry packages compare to the Hermitian QM
(HQM), which has a collection of packages with decades of development behind
them. Therefore, it is in great interest to develop a method that uses HQM
packages data as input and calculates complex physical quantities of resonances.
Such method was developed in our group, named Resonance via Pade (RVP).
The method is based on analytical dilation of real stabilization curves into the
complex plane and it has been successfully applied to many small molecular
systems.
This seminar will divide in two. First, I will present an ab initio NH investigation
of the resonance positions and decay rates for the low lying shape-type
states of uracil anion. In addition, the complex transition dipoles between these
resonance states were calculated. This work is the first application of the RVP
method to a medium-sized system. The ability to calculate ab initio energies
and lifetimes of biologically relevant systems paves the way for studying autoionization
reactions of such systems. Likewise, the ability to calculate their
complex transition dipoles opens the door for investigating the photo-induced
dynamics of biological molecules. Second, to emphasize the significance of those
abilities, I will present a theoretical concept for reducing the damage in RNA
done by the studied resonances of uracil anion using their complex physical
properties showed in the first part of the lecture.