PhD Student Uses Alternative Formalism to Explore Quantum Chemistry
Anael Ben-Asher is a talented young scientist who will complete her PhD this summer at Technion’s Schulich Faculty of Chemistry under the supervision of Prof. Nimrod Moiseyev, and then will continue on to post-doctoral work at the University of Madrid, Spain. Her PhD thesis, “Non-Hermitian Quantum Scattering Theory for Cold Molecular Collision Experiments,” uses alternative formalism to explore aspects of quantum chemistry that are rarely studied.
Anael, who is 28, is from the town of Carmiel in northern Israel. Already in high school she became interested in Chemistry and was accepted to the prestigious Archimedes program, during which she attended Chemistry classes at Technion throughout high school. In 2016, after receiving a BSc from Technion’s Schulich Faculty of Chemistry, Anael continued to a direct PhD track in the same faculty.
As a member of Prof. Moiseyev’s group, which researches novel phenomena in atomic, molecular and other systems that are hard to explain using standard quantum mechanics, Anael has focused on non-Hermitian quantum scattering theory, which is a framework for studying the involvement of metastable states in scattering process. “My Ph.D. research focuses on two types of systems. The first type is autoionization reactions, which commonly occur in cold molecular reaction experiments. The second type is the resonance tunneling process within quantum wells, on which some electronic devices are based,” she explains, adding that, “We are developing new techniques. It’s interesting because this field is different from standard quantum chemistry, and the way it’s being researched is innovative.”
Autoionization is a process by which an atom or molecule in an excited state spontaneously emits one of the outer-shell electrons. “I use the theory to describe the movement of nuclei in molecules when autoionization occurs. When two atoms collide, for example, and one is unstable, they produce a compound and after some time they detach and the electron escapes,” she elaborates.
These reactions were measured at very low temperatures of around 0.02 K in the lab of Prof. Edvardas Narevicius at the Weizmann Institute of Science. Calculations by Prof. Moiseyev’s group describe the processes in these experiments.
Anael has also researched other autoionization processes, in particular interatomic Coulombic decay (ICD) – a very efficient relaxation process of an electronically excited atom. This phenomenon is interesting, notes Anael, because atoms do not actually collide; they transfer energy from one to another without being close to each other.
Anael studied interatomic Coulombic decay using a dimer of a helium atom in an excited state and a lithium atom in its ground state. Since helium is a noble gas, when it is in an excited state it has high relaxation energy that is sufficient to ionize the lithium, since lithium is a metal and easy to ionize. When the energy is transferred from the helium to the lithium atom, the lithium becomes ‘lithium plus’ since it loses an electron.
For now, this research is purely theoretical, and no experiment has yet been carried out to confirm the results. Anael believes that this will happen soon, as there is a great deal of interest in this field.