Ultra-fast three and four-electron dynamics in intense electro-magnetic laser fields
Lead Research Organisation:
University College London
Department Name: Physics and Astronomy
Abstract
Ultra-short and ultra-intense laser pulses provide an impressive camera into the world of electron motion. Attoseconds and sub-femtoseconds are the natural time scale of multi-electron dynamics during the ionization and break-up of atoms and molecules. The overall aim of the proposed work is to investigate attosecond phenomena, pathways of correlated electron dynamics and effects due to the magnetic field of light in three and four-electron ionization in atoms and molecules triggered by intense near-infrared and mid-infrared laser pulses. Correlated electron dynamics is of fundamental interest to attosecond technology. For instance, an electron extracted from an atom or molecule carries information for probing the spatio-temporal properties of an ionic system with angstrom resolution and attosecond precision paving the way for holography with photoelectrons. Moreover, studies of effects due to the magnetic field of light in correlated multi-electron processes are crucial for understanding a variety of chemical and biological processes, such as the response of driven chiral molecules. Chiral molecules are not superimposable to their mirror image and are of particular interest, since they are abundant in nature.
The proposed research will explore highly challenging ultra-fast phenomena involving three and four-electron dynamics and effects due to the magnetic field of light in driven atoms and during the break-up of driven two and three-center molecules. We will investigate the physical mechanisms that underly these phenomena and devise schemes to probe and control them. Exploring these ultra-fast phenomena constitutes a scientific frontier due to the fast advances in attosecond technology. These fundamental processes are largely unexplored since most theoretical studies are developed in a framework that does not account for the magnetic field of light. Moreover, correlated three and four-electron escape is currently beyond the reach of quantum mechanical techniques. Hence, new theoretical tools are urgently needed to address the challenges facing attoscience.
In response to this quest, we will develop novel, efficient and cutting-edge semi-classical methods that are much faster than quantum-mechanical ones, allow for significant insights into the physical mechanisms, compliment experimental results and predict novel ultra-fast phenomena. These semi-classical techniques are appropriate for ionization processes through long-range Coulomb forces. Using these techniques, we will address some of the most fundamental problems facing attoscience. Our objectives are:
1) Identify and time-resolve novel pathways of correlated three-electron dynamics in atoms driven by near-infrared and mid-infrared laser pulses.
2) Explore effects due to the magnetic field of light in correlated two and three-electron escape during ionization in atoms as well as in two and three-center molecules driven by near-infrared and mid-infrared laser pulses that are either linearly or elliptically polarized or by vector beams, i.e. "twisted" laser fields, an intriguing form of light that twists like a helical corkscrew.
3) Control correlated multi-electron ionization and the formation of highly exited Rydberg states in four-active-electron three-center molecules by employing two-color laser fields or vector beams.
The proposed research will explore highly challenging ultra-fast phenomena involving three and four-electron dynamics and effects due to the magnetic field of light in driven atoms and during the break-up of driven two and three-center molecules. We will investigate the physical mechanisms that underly these phenomena and devise schemes to probe and control them. Exploring these ultra-fast phenomena constitutes a scientific frontier due to the fast advances in attosecond technology. These fundamental processes are largely unexplored since most theoretical studies are developed in a framework that does not account for the magnetic field of light. Moreover, correlated three and four-electron escape is currently beyond the reach of quantum mechanical techniques. Hence, new theoretical tools are urgently needed to address the challenges facing attoscience.
In response to this quest, we will develop novel, efficient and cutting-edge semi-classical methods that are much faster than quantum-mechanical ones, allow for significant insights into the physical mechanisms, compliment experimental results and predict novel ultra-fast phenomena. These semi-classical techniques are appropriate for ionization processes through long-range Coulomb forces. Using these techniques, we will address some of the most fundamental problems facing attoscience. Our objectives are:
1) Identify and time-resolve novel pathways of correlated three-electron dynamics in atoms driven by near-infrared and mid-infrared laser pulses.
2) Explore effects due to the magnetic field of light in correlated two and three-electron escape during ionization in atoms as well as in two and three-center molecules driven by near-infrared and mid-infrared laser pulses that are either linearly or elliptically polarized or by vector beams, i.e. "twisted" laser fields, an intriguing form of light that twists like a helical corkscrew.
3) Control correlated multi-electron ionization and the formation of highly exited Rydberg states in four-active-electron three-center molecules by employing two-color laser fields or vector beams.
Publications
Bhattacharya D
(2021)
Potential Energy Curves of Molecular Nitrogen for Singly and Doubly Ionized States with Core and Valence Holes.
in The journal of physical chemistry. A
Emmanouilidou A
(2023)
Singularity in the electron-core potential as a gateway to accurate multielectron ionization spectra in strongly driven atoms
in Physical Review A
Emmanouilidou A
(2023)
Singularity in electron-core potential as a gateway to accurate multi-electron ionization spectra in strongly driven atoms
in Physical Review A
Georgios Petros Katsoulis
(2024)
General model and toolkit for the ionization of three or more electrons in strongly driven molecules using an effective Coulomb potential for the interaction between bound electrons
in Physical Review A
Katsoulis G
(2021)
Signatures of magnetic-field effects in nonsequential double ionization manifesting as backscattering for molecules versus forward scattering for atoms
in Physical Review A
Katsoulis G
(2023)
Nondipole electron momentum offset as a probe of correlated three-electron ionization in strongly driven atoms
in Physical Review A
Katsoulis G
(2022)
Momentum scalar triple product as a measure of chirality in electron ionization dynamics of strongly driven atoms
in Physical Review A
Mountney M
(2022)
Mapping the direction of electron ionization to phase delay between VUV and IR laser pulses
in Physical Review A
| Description | We have solved a long standing problem in semi-classical techniques of how to treat artificial autoionization in multi-electron ionization. That is, classically an electron can come very close to a nucleus resulting in infinite potential energy due to the Coulomb singularity. This energy is transferred to the other bound electrons through the Coulomb interaction of bound electrons. To address this issue, we have developed a general formalism where we can treat exactly the interaction of each electron with the nucleus as well as the interaction of a quasi-free electron with the bound electrons, while we have devised a model interaction between bound electrons. Moreover, our state-of-the-art technique allows on the fly during time propagation to decide whether an electron is bound or quasifree and hence to turn on or off effective Coulomb potentials between electrons. We developed this technique for multi-electron ionization of atoms driven by intense, infrared laser pulses in 2022 and 2023. We have demonstrated in a Letter in Physical Review A that our technique is currently the best semi-classical technique 3-dimensional technique since it has excellent agreement with experimental results. Other classical techniques soften the Coulomb potential in order to treat artificial autoionization resulting in not being able to accurately reproduce experimental results. Moreover, currently there are reduced dimensionality quantum models to address triple electron ionization in atoms which again can not reproduce experimental results. Due to the complexity of the problem, 3-dimensional quantum techniques will not be available for years to come. Hence, our technique is a ground breaking one that will allow the study of ultrafast phenomena which were unexplored due to the lack of available theoretical techniques. We have been generalizing this technique to multi-electron ionization in molecules driven by intense, infrared pulses and our work has just been published in PRA (March 2024). Again this is a significant advance in the field since currently there are no other classical or quantum mechanical models that can address 3 or more electron ionization during the break-up of strongly-driven molecules. We will soon submit an EPSRC proposal where we describe how to further improve these models and how to employ them to discover new ultrafast phenomena and to understand currently theoretically unexplored experimental results |
| Exploitation Route | As mentioned above, we will soon be submitting an EPSRC proposal where we describe how to further improve these models and how to employ them to discover new ultrafast phenomena and to understand currently theoretically unexplored experimental results. Moreover, our papers published in 2022,2023 and 2024 describe in detail these advanced model for strongly driven atoms and molecules and hence can be implemented by other researchers in the field of ultrafast and attosecond science in order to explore currently unexplored ultrafast phenomena. Also, PDRAs budgeted on future proposals can be trained to use this advanced, non-mainstream techniques to address problems that currently very few if any other groups in the world can address. This transfer of knowledge will significant enhance attosecond and strong-field science in the UK. |
| Sectors | Digital/Communication/Information Technologies (including Software) Education |
| Description | As described in the key findings we have developed advanced theoretical and computational tools to describe ultrafast phenomena in strongly-driven atoms and molecules. The new ultrafast phenomena we have identified, we present in outreach interactions that are taking place at UCL involving for instance school kids in order to entice them to get involved with science and potentially study a field of natural sciences. |
| First Year Of Impact | 2022 |
| Sector | Digital/Communication/Information Technologies (including Software),Education |
| Impact Types | Societal |
| Title | Novel three-dimensional semiclassical model for multi-electron ionization in strongly driven atoms and molecules |
| Description | Correlated multi-electron ionization in atoms and molecules driven by intense infrared and mid-infrared laser pulses is a fundamental problem in attosecond and strong-field science. Currently, there are only very few three-dimensional quantum mechanical techniques that address two-electron ionization in strongly-driven atoms. Hence, it is no surprise that there are only a couple of quantum mechanical models of reduced dimensionality that address triple ionization in atoms. Also, the few classical models available for triple ionization soften the Coulomb potential for the interaction of each electron with the core. They do so, in order to address unphysical autoionization. That is, classically an electron can approach the nucleus at an infinitely small distance and gain infinite energy. Through the Coulomb interaction of a bound with another bound electron this energy is transferred to another electron that is unphysically ionized. However, softening the Coulomb potential results in inaccurate energies for electrons that return to the core with high energy, rescatter from the core and transfer energy to the other bound electrons. To address artificial autoionization, we developed a novel, state-of-the-art, three-dimensional model and also developed and implemented the computational tool for this model. In this model and computational tool, we fully account for the Coulomb singularity (do not soften the potential) between each electron and the core as well as between a re-colliding electron and a bound electron. In doing so, we accurately account for the transfer of energy of the recolliding electron to the bound electrons when it returns to the core. To avoid unphysical autoionization, we use effective potentials to describe the interaction between any pair of bound electrons. A highly novel element of our model and computational tool is that we determine on the fly, i.e. during time propagation, whether an electron is bound or recolliding. We do so using a set of simple criteria motivated by the transfer of energy in recollisions. Hence, on the fly, we decide whether a pair of electrons interact via the exact Coulomb potential or through an effective potential. |
| Type Of Material | Improvements to research infrastructure |
| Year Produced | 2022 |
| Provided To Others? | Yes |
| Impact | This method, model and computational tool for multi-electron ionization in strongly-driven atoms is general and although we have currently used it to address three-electron ionization it can easily be generalized to address more than three electron ionization in atoms. This theoretical method and computational tool is currently the only one that provides three-electron ionization spectra that are in excellent agreement with experimental results. It will significantly advance the field of attosecond and strong-field science, since this method will be used to address problems in multi-electron ionization that are currently out of reach for any other theoretical technique. |
| Title | Novel three-dimensional semiclassical model for multi-electron ionization in strongly driven molecules |
| Description | Correlated multi-electron ionization in molecules driven by intense infrared and mid-infrared laser pulses is a fundamental problem in attosecond and strong-field science. Currently, there are no three-dimensional quantum mechanical techniques that address three-electron ionization in strongly-driven molecules that also account for the motion of the nuclei. In addition, there are no accurate classical models that address triple ionization or more than three-electron ionization in molecules. Most other classical models for strongly-driven atoms or molecules soften the Coulomb potential. They do so, in order to address unphysical autoionization. That is, classically an electron can approach the nucleus at an infinitely small distance and gain infinite energy. Through the Coulomb interaction of a bound with another bound electron this energy is transferred to another electron that is unphysically ionized. However, softening the Coulomb potential results in inaccurate energies for electrons that return to the core with high energy, rescatter from the core and transfer energy to the other bound electrons. To address artificial autoionization in molecules, we developed a novel, state-of-the-art, three-dimensional model and also developed and implemented the computational tool for this model. In this model and computational tool, we fully account for the Coulomb singularity (do not soften the potential) between each electron and the core as well as between a re-colliding electron and a bound electron. In doing so, we accurately account for the transfer of energy of the recolliding electron to the bound electrons when it returns to the cores. This model that we have just developed for molecules is a generalization to moelcules of the model we have developed for atoms in 2022. To avoid unphysical autoionization, we use effective potentials to describe the interaction between any pair of bound electrons. A highly novel element of our model and computational tool is that we determine on the fly, i.e. during time propagation, whether an electron is bound or recolliding. We do so using a set of simple criteria motivated by the transfer of energy in recollisions. Hence, on the fly, we decide whether a pair of electrons interact via the exact Coulomb potential or through an effective potential. This is a ground breaking model and tool that will allow the study of strongly-driven molecules which has been hindered by the lack of accurate theoretical and computational techniques that can address the high complexity of ultrafast processes in strongly driven molecules. |
| Type Of Material | Improvements to research infrastructure |
| Year Produced | 2024 |
| Provided To Others? | Yes |
| Impact | It will have a major impact to the development of new experiments of strongly-driven molecules and understanding of fundamental ultrafast processes in strongly-driven molecules where multi-electron ionization and Coulomb explosion of the nuclei takes place. |
| URL | https://arxiv.org/pdf/2311.17533.pdf |
| Title | A novel, three-dimensional, semiclasical model for studing multi-electron ionization in atoms driven by intense fields |
| Description | As mentioned already in the research method and tool, we have developed a novel, three-dimensional model to address three and more than three electron ionization. This model and the resulting computational tool is general since it also accounts for the magnetic field of the laser pulse. Hence we can use it to account for non-dipole effects in triple ionization, an area of research currently completely unexplored. |
| Type Of Material | Computer model/algorithm |
| Year Produced | 2022 |
| Provided To Others? | Yes |
| Impact | This method and computational tool is currently the only one that provides multi-electron ionization spectra in excellent agreement with experimental results. It is expected that it will be used to explore correlated multi-electron ionization in atoms and identify signatures of non-dipole effects an area of research largely unexplored. |
| Description | Collaboration with LMU and Indian Institute of Technology Tirupati |
| Organisation | Ludwig Maximilian University of Munich (LMU Munich) |
| Country | Germany |
| Sector | Academic/University |
| PI Contribution | With my group at University College London, we have developed a state-of-the-art, novel three-dimensional semi-classical model that can describe ionization of three or more electrons in atoms. We are currently generalizing the theoretical framework and computational tool to account for diatomic and triatomic molecules. The first step in this model that describes the tunnel ionization of a valence electron is quantum-mechanical. For molecules these tunnel-ionization rates are provided by our collaborators Prof. Armin Scrinzi at Ludwig Maximillian University and by Assistant Prof Vinay Majety at the Indian Institute of Technology Tirupati. |
| Collaborator Contribution | As mentioned above they use a state-of-the-art quantum mechanical formulation and computational code to obtain tunnel ionization rates which are used in the tunneling step in our 3-dimensional semi-classical model. Our collaborators are one of very few groups in the world that can provide such accurate rates. |
| Impact | This collaboration is indeed multi-disciplinary. Our collaborators at LMU and the Indian Institute of Technology are leaders in ab-initio quantum mechanical techniques while the PI is a leader in developing semiclassical techniques to address multi-electron ionization triggered by intense infrared and mid-infrared laser pulses. |
| Start Year | 2022 |
| Description | National Research Council of Canada and University of Ottawa |
| Organisation | University of Ottawa |
| Country | Canada |
| Sector | Academic/University |
| PI Contribution | We have developed a state-of-the-art, novel, three-dimensional model for addressing three electron ionization in atoms and are currently working on generalizing this model to address three and four-electron ionization in atoms. Once we have obtained the triple ionization results, we develop simple analytical models to identify the underlying mechanisms in correlated multi-electron ionization. To do so, we extensively discuss with Prof. Paul Corkum a world leader in attosecond science as well as Dr. Andre Staudte. Being both experimentalists, they also give us the experimental viewpoint in our theoretical work and help us identify the mechanisms underlying multi-electron escape and what laser pulses to use in order to experimentally measure these mechanisms. |
| Collaborator Contribution | As mentioned above, Prof. Paul Corkum as well as Dr. Andre Staudte, being both experimentalists, they give us the experimental viewpoint in our theoretical work and help us identify the mechanisms underlying multi-electron escape and what laser pulses to use in order to experimentally measure these mechanisms. Moreover, we discuss with them for possible future experiments to identify the mechanisms we predict with our theoretical work. |
| Impact | Prof. Paul Corkum has contributed through extensive discussions with him in our paper on triple ionization of Ne which has been published in Phys. Rev. A 107, L041101 (2023). This is a ground breaking paper since it demonstrates that our novel, three-dimensional model provides distributions for the sum of the three-electron final momenta that are in excellent agreement with experiments. Currently, this is the only model out of the very few existing ones, that provides such excellent agreement with experiment. |
| Start Year | 2021 |
| Description | National Research Council of Canada and University of Ottawa |
| Organisation | University of Ottawa |
| Country | Canada |
| Sector | Academic/University |
| PI Contribution | We have developed a state-of-the-art, novel, three-dimensional model for addressing three electron ionization in atoms and are currently working on generalizing this model to address three and four-electron ionization in atoms. Once we have obtained the triple ionization results, we develop simple analytical models to identify the underlying mechanisms in correlated multi-electron ionization. To do so, we extensively discuss with Prof. Paul Corkum a world leader in attosecond science as well as Dr. Andre Staudte. Being both experimentalists, they also give us the experimental viewpoint in our theoretical work and help us identify the mechanisms underlying multi-electron escape and what laser pulses to use in order to experimentally measure these mechanisms. |
| Collaborator Contribution | As mentioned above, Prof. Paul Corkum as well as Dr. Andre Staudte, being both experimentalists, they give us the experimental viewpoint in our theoretical work and help us identify the mechanisms underlying multi-electron escape and what laser pulses to use in order to experimentally measure these mechanisms. Moreover, we discuss with them for possible future experiments to identify the mechanisms we predict with our theoretical work. |
| Impact | Prof. Paul Corkum has contributed through extensive discussions with him in our paper on triple ionization of Ne which has been published in Phys. Rev. A 107, L041101 (2023). This is a ground breaking paper since it demonstrates that our novel, three-dimensional model provides distributions for the sum of the three-electron final momenta that are in excellent agreement with experiments. Currently, this is the only model out of the very few existing ones, that provides such excellent agreement with experiment. |
| Start Year | 2021 |
| Description | Invited talk of the PDRA budgeted in the proposal |
| Form Of Engagement Activity | Participation in an activity, workshop or similar |
| Part Of Official Scheme? | No |
| Geographic Reach | International |
| Primary Audience | Other audiences |
| Results and Impact | Dr. Georgios Katsoulis, who is the PDRA budgeted on the proposal, has delivered an invited talk on the research of this proposal at the International conference Atto-FEL 2022 that took place at University College London at the end of June 2022. The audience was Postgraduate students and Leaders in the field of Attosecond and Strong Field Science. |
| Year(s) Of Engagement Activity | 2022 |
| Description | Presentation as a poster of the PDRA budgeted in the proposal |
| Form Of Engagement Activity | Participation in an activity, workshop or similar |
| Part Of Official Scheme? | No |
| Geographic Reach | International |
| Primary Audience | Postgraduate students |
| Results and Impact | Dr. Georgios Katsoulis who is the PDRA budgeted on the proposal has presented the work relevant to this proposal in the international conference ICPEAC2023 that took place in Ottawa from July 25th to August 1st, 2023. |
| Year(s) Of Engagement Activity | 2023 |