| NSF Org: |
PHY Division Of Physics |
| Recipient: |
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| Initial Amendment Date: | July 18, 2019 |
| Latest Amendment Date: | July 18, 2019 |
| Award Number: | 1912093 |
| Award Instrument: | Standard Grant |
| Program Manager: |
Robert Forrey
PHY Division Of Physics MPS Directorate for Mathematical and Physical Sciences |
| Start Date: | August 1, 2019 |
| End Date: | July 31, 2023 (Estimated) |
| Total Intended Award Amount: | $117,226.00 |
| Total Awarded Amount to Date: | $117,226.00 |
| Funds Obligated to Date: |
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| History of Investigator: |
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| Recipient Sponsored Research Office: |
CAMPUS BOX 1100 NORMAL IL US 61790-1100 (309)438-2528 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
Normal IL US 61790-1000 |
| Primary Place of
Performance Congressional District: |
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| Unique Entity Identifier (UEI): |
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| Parent UEI: |
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| NSF Program(s): | AMO Theory/Atomic, Molecular & |
| Primary Program Source: |
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| Program Reference Code(s): |
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| Program Element Code(s): |
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| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.049 |
ABSTRACT
Atomic collisions are a well-established method for probing the structure of atoms and molecules, as well as understanding the dynamics of how charged particles interact with matter. Due to their quantum mechanical nature, the particles involved in the collision must be modeled as matter waves, not as individual point particles. In the last decade, particles with unique waveforms have been created. These new matter waveforms (known as vortex waves or twisted particles) have properties that offer the opportunity for control and rotation of nanoparticles and improved resolution in electron microscopy, as well as the study of fundamental atomic properties, such as the magnetic moment and atomic transitions. Currently, there is a very limited understanding of how twisted particles interact with individual atoms or molecules. In order to realize the proposed applications, it is necessary to develop theoretical models that describe the particles' interaction with atoms at the most basic level. The researchers will develop and apply theoretical models to describe the physics of collisions between twisted particles and atoms in order to explain recently observed quantum phenomena and provide guidance for future experiments and applications. In addition to the science, another key aspect of the project is the inclusion of undergraduate students in cutting-edge research and the training of the next generation of physicists. Participation in this project provides students with valuable hands-on research experience through conceptual development of the models, as well as implementation and analysis. The students will also present their results at regional and national conferences, giving them a more global view of scientific research and encouraging them to pursue careers in STEM fields.
The goals of the project will be accomplished through the development of two distinct computational models. All of the models will be designed for use on high performance computers and will be parallelized to improve efficiency. One of the models is based on the time-dependent Path Integral Quantum Trajectory (PIQTr) method that utilizes a Lagrangian approach to quantum mechanics. This model will be applied to phenomena such as electron capture, coherence, diffraction, tunneling, and quantum reflection. Application of the PIQTr model to higher dimensional systems will require the implementation of numerical techniques, such as adaptive stepsize, Monte Carlo integration, and boundary matching techniques. The results of the PIQTr model will provide a time-dependent analysis of collision processes allowing researchers to view the evolution of the interaction. A second model will be developed for the study of electron vortex beam collisions with atoms. This model will provide insight into orbital angular momentum transfer, as well as orientation and rotation effects that may occur during the collision process. A multipole expansion of the collision transition amplitude will yield information regarding potential selection rules or the possibility of state selectivity. The results of the electron vortex beam studies will be in the form of collision cross sections that can be used to provide guidance to experimentalists and others interested in applications of electron vortex beams.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
PUBLICATIONS PRODUCED AS A RESULT OF THIS RESEARCH
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PROJECT OUTCOMES REPORT
Disclaimer
This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.
The research conducted with this grant focused on understanding the interaction of charged particles with matter in the context of collisions between electrons and individual atoms or molecules. Electron collisions are a well-established method for probing the structure of atoms and molecules, and over the last decade new types of electron waveforms have been created. These wave forms are known as twisted electrons or sculpted electrons. Twisted electrons have the same charge and mass as traditional electrons, but their matter waveforms are different. These new twisted electrons open the door to many novel applications, including control and rotation of nanoparticles, improved resolution in electron microscopy, as well as new techniques to study fundamental atomic properties. One of the goals of this grant was to establish how twisted electrons interact with atoms and molecules in order to provide the fundamental information necessary for developing applications that use twisted electrons.
Intellectual Merit: We developed new theoretical methods to simulate interactions between twisted electrons and sculpted wave packets with matter. Our group performed the first simulations of ionization (removal of an electron from an atom) by twisted electrons and we showed that the mechanisms of ionization by twisted electrons are different than those of traditional electrons. When twisted electrons collide with atoms, they cause secondary electrons from the atom to be emitted in different locations and with different intensity than traditional electron projectiles. In many applications, the production of secondary electrons through ionization can cause negative effects. For example, in biological tissue, secondary electrons from collisions can cause damage to healthy tissue. In microscopy applications, secondary electrons may result in a loss of resolution or damage to the sample under observation. Our work has demonstrated that twisted electrons interact differently with matter than traditional electrons, which may lead to greater means of controlling secondary electrons and their negative effects.
Our research has also demonstrated that twisted electrons and other sculpted matter waveforms can be used to control the fundamental dynamics of charged particle interactions. The results of our simulations indicated that the properties of twisted electrons can provide an additional control mechanism for the localization of the electron wave packet, known as coherence. By controlling the electron’s coherence, it is possible to control with which parts of a target atom or molecule the electron interacts. Additionally, we showed that sculpted matter waveforms exhibit different dynamics that traditional matter wave forms. We established that by controlling the sculpted waveform’s phase (a property unique to sculpted waveforms), it is possible to control its arrival time after transmission through a barrier. The ability to control the wave packet’s arrival time is unique to sculpted particles and may provide a new tool to study electron dynamics in greater detail.
Broader Impacts: The results of our research demonstrate the unique properties of twisted electrons and sculpted matter waveforms and how these properties can be used for greater control of particles and interactions at the atomic scale. This work has implications in many applied physics fields and may influence the development of new technologies and our ability to control particles at ever smaller scales. In addition to the science, another important objective of our grant was the involvement and training of undergraduate students in physics research. During the grant, 3 undergraduate students participated in our research, each for multiple years. The students were trained in the latest physics and computational techniques. Collectively, they coauthored 4 papers in peer-reviewed journals and gave 10 presentations at regional and national conferences. By attending and presenting at conferences, students gain valuable networking experience, exposure to cutting edge scientific research, as well as practice communicating their work to a wider audience. Their participation in research provided them with experiences, training, and skills not accessible through the traditional university curriculum. These research experiences make our graduates valuable contributors to the science and technology workforce. All of our students have gone onto careers in science fields or are pursuing graduate degrees in physics, contributing to the pipeline of talent that is needed in these areas. All of our group’s research is published in peer-reviewed journals and available open access through arxiv.org.
Last Modified: 11/28/2023
Modified by: Allison L Harris
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