Research

Our current research in details.
Positronium collisions with ions, atoms, and molecules

Positronium (Ps) is a bound state of an electron and a positron. Ps scattering from atoms and molecules has interesting similarities to that of electron scattering from atoms and molecules. A charge-transfer reaction between Ps and an antiproton can generate antihydrogen which is important for experiments that test the fundamental symmetry laws of our universe. We perform inelastic Ps scattering calculations with different targets in order to explain experimental results and provide theoretical estimates for antiydrogen experiments

Recent publications

  1. H. B. Ambalampitiya, D.V. Fursa, A. S Kadyrov, I. Bray and I. Fabrikant, “Charge transfer in positronium-proton collisions: Comparison of classical and quantum mechanical theories”, J. Phys. B 53, 155201 (2020). Link
  2. R. S. Wilde and I. I. Fabrikant, "Positronium collisions with atoms and molecules", J. Phys.: Conf. Ser. 1412, 052011 (2020). Link
  3. R. S. Wilde and I. I. Fabrikant, "Resonant scattering of positronium atoms by nitrogen molecules ", J. Phys. B 53, 185202 (2020). Link

An animation of a Ps-(anti)proton collision leading to the formation of (anti)hydrogen. 

                                                  

Laser-assisted electron-ion processes

In the semiclassical limit, we study various electron-ion processes in the presence of a laser field. Interesting phenomena such as Coulomb focusing and chaotic scattering can have striking effects on the computed probabilities and cross sections

Recent publications

  1. I. I. Fabrikant and H. B. Ambalampitiya, “Laser-assisted spontaneous radiative recombination”,
    Phys. Rev. A 101, 053401 (2020). Link

  2. H. B. Ambalampitiya and I. I. Fabrikant, “Classical theory of laser-assisted spontaneous bremsstrahlung”, Phys. Rev. A 99, 063404 (2019). Link

A schematic of an electron's classical path undergoing spontaneous bremsstrahlung in the presence of a laser field and a Coulomb center.

                                                                    

Dissociative electron attachment

Dissociative electron attachment or DEA has many practical applications in medicine, industry, and astrophysics. In DEA, a low-energy electron can break up a large molecule via a resonant attachment process. We develop full quantum mechanical as well as semiclassical theories to treat DEA  when the molecule has more than one degree of vibrational freedom.

Recent publications

  1. H. B. Ambalampitiya and I. I. Fabrikant, “Nonlocal theory of dissociative electron attachment: Inclusion of two vibrational modes” , Phys. Rev. A 102, 022801 (2020). Link

Schematic of potential energy curves/cuts for qualitative explanation of the DEA process.

                                                                            

Semiclassical methods in AMO physics

A combination of classical and quantum ideas is the best way to comprehend and answer many problems in quantum mechanics. Not only semiclassical methods are highly intuitive,  but they are also the only path for solution when exact quantum calculations are unfeasible. We apply semiclassical Van Vleck-Gutzwiller propagator formalism, WKB, and classical trajectory Monte Carlo (CTMC) methods to solve our current and new research problems.

Publications

  1. I. I. Fabrikant, "Interference effects in photodetachment and photoionization of atoms in homogeneous electric field", Sov. Phys. JETP 52, 1045 (1980).

  2. H. B. Ambalampitiya and I. I. Fabrikant, “Photodetachment microscopy in time dependent fields”, Phys. Rev. A 95, 053414 (2017). Link

A semiclassical simulation of spatial and temporal interference structure in the electron current density of a photodetachment microscopy experiment in a time-dependent field.