Bulletin of the American Physical Society
54th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 68, Number 7
Monday–Friday, June 5–9, 2023; Spokane, Washington
Session E03: Applied Collisions and Related ProcessesInvited Live Streamed
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Chair: Brant Bowers, University of Washington Room: Ballroom 111 B |
Tuesday, June 6, 2023 2:00PM - 2:30PM Withdrawn |
E03.00001: A Dirac-R-matrix approach in support of the interpretation of spectra from magnetically-confined plasmas and kilonovae. Invited Speaker: Connor Ballance The DARC (Dirac Atomic R-matrix Code) may be employed as a non-perturbative approach to electron-impact excitation/ionisation/recombination and photoionisation[1]. Fundamentally, the atomic structure and subsequent collisional rates are an integral part of subsequent collisional-radiative models and radiative transport simulations. Within the remit of this Applied Collisions session we shall consider two examples, namely the interpretation of the electro-magnetic counterpart of a neutron star merger (kilonova) GW170817 and the impurity influx from the plasma facing components of tokamak divertors. Both examples consider overlapping elements from Z=74 to Z=79 of the periodic table. |
Tuesday, June 6, 2023 2:30PM - 3:00PM |
E03.00002: Defying Boltzmann Equilibrium: Recent Advances in Nuclear Spin Hyperpolarization Invited Speaker: Rosa T Branca In the past 10 years the field of NMR and MRI has been revolutionized by the development of novel techniques that enable rapid and efficient transfer of spin order from electrons to nuclei and from nuclei to other nuclei. With respect to thermal equilibrium, these techniques can enhance the nuclear spin polarization by several orders of magnitude, enabling detection of nuclear spins and molecules that normally are invisible to induction-based NMR detection methods. In this talk I will give a broad overview of the field of nuclear spin polarization, as it has evolved in recent years, with a special emphasis on nuclear spin polarization of noble gases, recent technical developments, and novel biological applications it enabled. |
Tuesday, June 6, 2023 3:00PM - 3:30PM |
E03.00003: Atomic and Molecular Collision Models and Data for Plasma Modeling Invited Speaker: Mark C Zammit Non-equilibrium swarm and plasma modeling are active areas of research for academic, industrial, energy, and safety applications, which requires input of atomic and molecular physics and data. Modeling swarms, plasmas and streamers are complex physics and computational problems that couple particle kinetics (including those due to photons), electric and magnetic fields, and sometimes plasma-material interactions, in order to understand the interplay between microscopic and macroscopic processes. Over the last decade or so, Monte Carlo particle-in-cell and Boltzmann solver codes have been used to study several aspects of these problems and are the primary tools of use to understand macroscopic plasma properties, such as particle fluxes and energies, electric currents, etc. However, a major uncertainty in these modeling tools is the availability and accuracy of the input collision and photon-absorption cross sections, which are particularly difficult to calculate for low-temperature plasmas, where near-neutral atoms and molecules, and excited state species are abundant.
In this talk we will overview the tools we utilize to generate atomic and molecular data, recommend new collision models for efficient application in Monte Carlo particle-in-cell codes, and showcase the impact of these new data and models in plasma or swarm simulations. |
Tuesday, June 6, 2023 3:30PM - 4:00PM |
E03.00004: Positron Collisions with Cold Atoms Invited Speaker: Josh R Machacek The electron and its antiparticle, the positron, can form a hydrogenic bound state known as positronium in collisions with atoms and molecules. Cold atom targets (e.g., magneto-optical traps or MOTs) have become ubiquitous in the investigation of quantum correlations in many-body electronic systems, while the advent of the Surko trap has enabled the production of tailored room temperature positrons beams. These beams have been used to investigate positron binding in molecular systems where manybody affects play an important role. Our current work is focused on cold atomic systems (e.g., Rb) in a well-defined quantum state which can be manipulated before interaction with a room-temperature positron beam. The beam is formed from positrons obtained from nuclear beta decay. Hence, they have helicity due to the non-conservation of the weak interaction. It has been demonstrated that positrons do not suffer significant depolarization as a result of moderation or trapping/cooling collisions and thus, a positron beam obtained from a Surko trap will have a non-zero helicity. Positronium atoms produced, in the ground state or excited state, in collisions with atoms or molecules have either singlet or triplet character and are unstable to annihilation into 2 or 3 gamma rays, respectively. In collisions with a Rb-MOT target, the quantization axis of the spin-polarised Rb atoms can be varied with respect to the helicity of the incident positron beam. We will discuss the prospects to use this system for quantum mechanically complete experiments involving antimatter. |
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