Semi-classical models for ultra-fast multi-electron phenomena in intense electro-magnetic laser fields
Lead Research Organisation:
University College London
Department Name: Physics and Astronomy
Abstract
Attoscience is one of the great scientific challenges of the 21st century. Attoseconds and sub-femtoseconds are the natural time scale for multi-electron effects during the ionization and break-up of atoms and molecules. The proposed research will explore the physical mechanisms underlying correlated
multi-electron dynamics and devising schemes to probe/control these mechanisms. Correlated electron dynamics is of fundamental interest to
attosecond technology. For instance, an electron extracted from a molecule carries information determining the electronic molecular orbital and
position of the nuclei, thus paving the way for molecular imaging. Moreover, the proposed work will explore magnetic field and quantum interference
effects on attosecond processes. These effects are crucial for fully understanding many phenomena, such as the generation of attosecond pulses and
holography with photoelectrons.
The overall aim of the proposed work is to explore attosecond phenomena, magnetic field and interference effects during multi-electron ionization in atoms and multi-center molecules triggered by ultra-short and ultra-strong near-infrared and mid-infrared laser pulses. The rapid experimental advances place these phenomena at the forefront of Attoscience. New theoretical tools are urgently needed to address the challenges facing this field. In response to this quest, I offer novel, efficient and sophisticated semi-classical methods that are much faster than quantum-mechanical ones and that allow for significant insights into the physical mechanisms. These semi-classical techniques are appropriate for ionization processes through long-range Coulomb forces. Using these techniques, I will address some of the most fundamental problems facing Attoscience. My objectives are:
1) Account for non-dipole effects to explore photon momentum sharing between electrons and ions in two-electron atoms and diatomic molecules driven by near-IR and mid-IR laser pulses.
3) Account for non-dipole and interference effects to explore "frustrated" ionization and non-sequential double ionization in two-electron atoms and diatomic molecules
driven by mid-IR laser pulses.
4) Explore non-sequential and "frustrated" ionization in two- and three-electron three-center molecules driven by near-IR laser pulses.
multi-electron dynamics and devising schemes to probe/control these mechanisms. Correlated electron dynamics is of fundamental interest to
attosecond technology. For instance, an electron extracted from a molecule carries information determining the electronic molecular orbital and
position of the nuclei, thus paving the way for molecular imaging. Moreover, the proposed work will explore magnetic field and quantum interference
effects on attosecond processes. These effects are crucial for fully understanding many phenomena, such as the generation of attosecond pulses and
holography with photoelectrons.
The overall aim of the proposed work is to explore attosecond phenomena, magnetic field and interference effects during multi-electron ionization in atoms and multi-center molecules triggered by ultra-short and ultra-strong near-infrared and mid-infrared laser pulses. The rapid experimental advances place these phenomena at the forefront of Attoscience. New theoretical tools are urgently needed to address the challenges facing this field. In response to this quest, I offer novel, efficient and sophisticated semi-classical methods that are much faster than quantum-mechanical ones and that allow for significant insights into the physical mechanisms. These semi-classical techniques are appropriate for ionization processes through long-range Coulomb forces. Using these techniques, I will address some of the most fundamental problems facing Attoscience. My objectives are:
1) Account for non-dipole effects to explore photon momentum sharing between electrons and ions in two-electron atoms and diatomic molecules driven by near-IR and mid-IR laser pulses.
3) Account for non-dipole and interference effects to explore "frustrated" ionization and non-sequential double ionization in two-electron atoms and diatomic molecules
driven by mid-IR laser pulses.
4) Explore non-sequential and "frustrated" ionization in two- and three-electron three-center molecules driven by near-IR laser pulses.
Planned Impact
The proposed work is on exploring attosecond phenomena, magnetic field and interference effects during the ionization of multi-electron
atoms and molecules driven by ultra-intense near-infrared and mid-infrared laser pulses. Understanding the electronic motion on an attosecond time-scale in atomic and
molecular systems will be of importance in the future for a number of industries that closely work with applied researchers in order to enhance the industries' capabilities.
My research will be communicated to these applied researchers through academic dissemination and also through direct interaction with them at the London Center for Nanotechnology (LCN). LCN aims to provide the nanoscience and nanotechnology needed to solve major problems in information processing, health care, and energy and environment. In the sense mentioned above, my research will contribute in addressing problems in economy, health care and information processing.
Specifically, one of the goals of the proposed research is to explain magnetic field effects in strong-field phenomena and in particular photon momentum sharing in atoms and molecules. The combined momenta of the photons can give rise to radiation pressure which has significant applications in the generation of terahertz radiation.
There is a fast growing interest in terahertz radiation. The reason is that it has a wide range of applications, such as manufacturing, inspection of packaged goods and remote sensing. Terahertz radiation is also non-ionizing and thus it can not damage DNA making terahertz radiation safe for medical imaging.
Moreover, one of the goals of the proposed research is to understand and control the attosecond electronic motion in molecules. Controlling electron motion in molecules
and solid state structures opens up the way for researching technologies that may lead to speeding up current electronics by several orders of magnitude.
Namely, the density of information flow, such as operations performed by a computer, is determined by how fast the electron current can be switched on and off in a
digital chip. The current state-of-the-art in electronic circuits dictates a switching time within a fraction of a nanosecond. To achieve higher density of information, faster switching times need to be achieved, such as attoseconds. The latter is the natural time-scale for electronic motion in neighboring atoms in a crystal lattice or in a small molecule.
atoms and molecules driven by ultra-intense near-infrared and mid-infrared laser pulses. Understanding the electronic motion on an attosecond time-scale in atomic and
molecular systems will be of importance in the future for a number of industries that closely work with applied researchers in order to enhance the industries' capabilities.
My research will be communicated to these applied researchers through academic dissemination and also through direct interaction with them at the London Center for Nanotechnology (LCN). LCN aims to provide the nanoscience and nanotechnology needed to solve major problems in information processing, health care, and energy and environment. In the sense mentioned above, my research will contribute in addressing problems in economy, health care and information processing.
Specifically, one of the goals of the proposed research is to explain magnetic field effects in strong-field phenomena and in particular photon momentum sharing in atoms and molecules. The combined momenta of the photons can give rise to radiation pressure which has significant applications in the generation of terahertz radiation.
There is a fast growing interest in terahertz radiation. The reason is that it has a wide range of applications, such as manufacturing, inspection of packaged goods and remote sensing. Terahertz radiation is also non-ionizing and thus it can not damage DNA making terahertz radiation safe for medical imaging.
Moreover, one of the goals of the proposed research is to understand and control the attosecond electronic motion in molecules. Controlling electron motion in molecules
and solid state structures opens up the way for researching technologies that may lead to speeding up current electronics by several orders of magnitude.
Namely, the density of information flow, such as operations performed by a computer, is determined by how fast the electron current can be switched on and off in a
digital chip. The current state-of-the-art in electronic circuits dictates a switching time within a fraction of a nanosecond. To achieve higher density of information, faster switching times need to be achieved, such as attoseconds. The latter is the natural time-scale for electronic motion in neighboring atoms in a crystal lattice or in a small molecule.
People |
ORCID iD |
| Agapi Emmanouilidou (Principal Investigator) |
Publications
Chen A
(2017)
Non-sequential double ionization with near-single cycle laser pulses.
in Scientific reports
Chen A
(2016)
Frustrated double ionization in two-electron triatomic molecules
in Physical Review A
Chen A
(2016)
Frustrated double and single ionization in a two-electron triatomic molecule H + 3
in Journal of Physics B: Atomic, Molecular and Optical Physics
Emmanouilidou A
(2017)
Recollision as a probe of magnetic-field effects in nonsequential double ionization
in Physical Review A
Emmanouilidou A
(2017)
Non-dipole recollision-gated double ionization and observable effects
in Journal of Physics B: Atomic, Molecular and Optical Physics
G. P. Katsoulis
(2019)
Fingerprints of slingshot non-sequential double ionization on two-electron probability distributions
in Scientific Reports
Georgios Petros Katsoulis
(2021)
Signatures of magnetic field effects in non-sequential double ionization manifesting as back-scattering for molecules versus forward-scattering for atoms
in Physical Review A
Katsoulis G
(2020)
Enhancing frustrated double ionization with no electronic correlation in triatomic molecules using counter-rotating two-color circular laser fields
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
| Description | My team and I have developed three-dimensional semi-classical techniques to tackle magnetic field effects in double ionization of two-electrons atoms driven by intense and ultra-short infrared laser fields. Using these techniques we were able to identify a new magnetic field phenomenon, namely, non-dipole re-collision gated ionization. That is, the magnetic field and the re-collision act as a gate which results in favoring initial momenta, of the electron that tunnel-ionizes in the initial state, in the direction opposite to the propagation direction of the field. This asymmetry in the initial momentum results in asymmetries on the electron spectra of the two escaping electrons that can be measured experimentally. Moreover, we have developed a state-of-the-art three-dimensional semi-classical theoretical and computational tool that allows us to investigate multi-electron ionization during the break-up of two-electron triatomic molecules. These ultrafast phenomena are currently out of reach for quantum mechanical techniques. The tools we develop can be currently developed by very few people in the world. Using this cutting-edge tool we investigated double ionization and frustrated double ionization during the break-up of molecules. In the latter process one electron ionizes but the second one remains bound in a highly Rydberg state. Our results were found to be in very good agreement with experimental results. In addition, we have demonstrated attosecond control, that is, we have demonstrated how the electron-electron correlation can be turned on and off by employing two color laser fields and varying the time delay between the two pulses. With these studies we open the way for future experiments on attosecond control. In a very recent study, we have identified yet another mechanism of Rydberg formation in strongly-driven diatomic and triatomic molecules. That is, in 2012 we have identified two major mechanisms for Rydberg formation, with the electron that remains bound undergoing frustrated ionization either in the first step or the second one. For linear fields we have found that electron-electron correlation is important in the mechanism of Rydberg formation where the first step of ionization is frustrated. In this very recent study, we have found significant enhancement of Rydberg formation via a mechanism where the first ionization step is frustrated but there is no electron-electron correlation. This mechanism is dominant when a two-electron triatomic molecule is driven by two counter propagating laser fields. In addition, by varying the ratio of the strengths of the two laser fields we have demonstrated control of the mechanism of Rydberg formation. We have identified a new mechanism of non-sequential double ionization in atoms driven by laser fields at small intensities. This mechanism we named slingshot non-sequential double ionization. With this mechanism we demonstrated how important the role of the Coulomb force that an electron experiences from the nucleus is in double ionization of atoms driven by intense laser fields. This Coulomb slingshot motion is similar to the gravitational slingshot that alters the motion of a spacecraft around a planet. The hallmark of this new mechanism is that the two electrons escape in opposite directions along the laser field. Currently experiments are on their way at LMU University in Germany in order to identify experimentally this new mechanism. Moreover, in a very recent study of Ar driven by two orthogonally polarised laser fields, together with our experimental collaborators at NRC in Ottawa Canada, we have paved the way for streaking the ionization time of the two electrons escaping in double ionization. Moreover, in the last few months, we have developed a powerful theoretical technique and computational tool that has allowed us to perform ground breaking studies of magnetic field effects in non-sequential double ionization during the break-up of two-electron diatomic molecules. Specifically, we have found that the re-colliding electron backscatters along the direction of light propagation resulting in both electrons escaping with a large negative average sum of the final momenta. This is in striking contrast to atoms where the re-colliding electron forward scatters and both electrons escape with a large positive average sum of the final electron momenta. Very interestingly, these magnetic field phenomena are observed at laser field intensities which are significantly smaller than the intensities previously expected to give rise to magnetic field effects. Moreover, during this last year we have achieved the first steps towards acounting for more than two electrons in molecules driven by intense laser fields. Currently, ab-initio quantum calculations can only address up to two-electron dynamics in strongly-driven atoms and molecules with fixed nuclei. We are currently one of teh very few groups in the world which can address three-electron dynamics in strongly-driven systems. In the coming year we will improve our model for treating three-electron dynamics and perform ground breaking studies on strongly-driven molecules |
| Exploitation Route | The computational and theoretical tools we develop can be used by researchers in other fields of science to study attosecond phenomena. Moreover, we are now using these tools as a stepping stone to develop techniques that address magnetic field effects in molecules and also tackle three-electron triatomic molecules which is a highly challenging problem. Slingshot non sequential double ionization is a new mechanism of double ionization in strong-field physics that we identified in 2018. We expect that our finding will motivate several new theoretical and experimental studies. Moreover, our studies on the mechanisms of Rydberg formation have significant impact in the attosecond science community. Namely, experiments are performed to identify the different mechanisms we have identified for Rydberg formation in molecules. Also, several theoretical studies motivated by our studies of the effect of electron-electron correlation in Rydberg formation in molecules, study the effect of electronic correlation in Rydberg formation in strongly-driven atoms. Our studies of magnetic field effects of two-electron molecules in diatomic molecules will be generalized to three and four center molecules in order to provide theoretical support for experimental studies of chiral molecules driven by intense fields where the magnetic field of light plays a crucial role. |
| Sectors | Digital/Communication/Information Technologies (including Software),Education |
| Description | I have been communicating the results of my research to junior high and high school students with the aim to educate young students about ultrafast phenomena and laser technologies and inspire them to follow a career path in science. |
| First Year Of Impact | 2016 |
| Sector | Education |
| Description | Ultra-fast three and four-electron dynamics in intense electro-magnetic laser fields |
| Amount | £430,851 (GBP) |
| Funding ID | EP/W005352/1 |
| Organisation | Engineering and Physical Sciences Research Council (EPSRC) |
| Sector | Public |
| Country | United Kingdom |
| Start | 12/2021 |
| End | 11/2024 |
| Title | Magnetic field effects in molecules |
| Description | The last year we have developed a state-of-the-art three-dimensional semi-classical technique to be able to describe magnetic field effects in two-electron diatomic molecules driven by intense laser fields. This is a unique tool since we are currently maybe the only group in the world which can account for the magnetic field of light in our calculations. |
| Type Of Material | Improvements to research infrastructure |
| Year Produced | 2021 |
| Provided To Others? | Yes |
| Impact | Using this sophisticated 3-d semi-classical technique we have predicted that the re-colliding electron backscatters in teh direction of light prropagation in striking contrast to the re-colliding electron forward-scattering in two-electron atoms driven by intense laser fields. The final average sum of the electron momenta along the direction of lught propagation is large and negative for molecules in contrast to atoms. This occurs at intensities where it was previously expected that magnetic field effects do not have a large effect. |
| Title | Three-electron dynamics in systems driven by intense laser fields |
| Description | The last year we have taken the first steps towards developing a state-of-the-art 3-d semi-classical tool to describe three-electron dynamics during the break-up of triatomic molecules driven by intense laser fields. Currently, ab-initio quantum mechanical techniques are restricted to the study of double ionization in atoms and diatomic molecules with fixed nuclei. Hence, this tool will significantly advance the field of ultra-fast science since it is one of the very few that will allow the study of multi-electron dynamics in molecules driven by intense fields. |
| Type Of Material | Improvements to research infrastructure |
| Year Produced | 2021 |
| Provided To Others? | Yes |
| Impact | Using the above tool, we were able to study for the first time triple frustrated ionization, where two electron escape while one stays in ahigh Rydberg state during the break-up of H_{2}He^{+}. |
| Title | Two-electron dynamics in ultra-short and intense electromagnetic fields |
| Description | The last few months we have developed in my group a new state-of-the-art theoretical and computational tool to describe the two-electron dynamics in intense and ultra-short laser pulses. The innovative aspect and strength of this theoretical technique and computational tool is that it allows one to account for non-dipole effects, i.e. the effect of the magnetic field, in strongly-driven molecules. The vast majority of strong-field studies use the dipole approximation to describe strongly-driven molecules and in most studies the nuclei are fixed. This powerful computational tool will allow our group to perform the first studies of magnetic field effects during the break-up of strongly driven diatomic and triatomic molecules. In the next few months we will investigate the effect of the magnetic field in the different mechanisms of Rydberg formation, we have introduced the latter a few years ago, as well as the magnetic effects on non-sequential double ionization. This tool along with the magnetic field effects will be published in the next few months. |
| Type Of Material | Improvements to research infrastructure |
| Year Produced | 2020 |
| Provided To Others? | No |
| Impact | This tool will have significant impact on studies of magnetic field effects during the break-up of strongly-driven multi-centre molecules. It will also allow to perform studies of magnetic field effects on non-sequential double ionization, which have never been performed before. |
| Title | Semi-classical model to account for three-electron dynamics in strongly-driven molecules |
| Description | We developed a state-of-the-art semiclassical model that account for three-electron dynamics during the break-up of triatomic molecules. |
| Type Of Material | Computer model/algorithm |
| Year Produced | 2021 |
| Provided To Others? | Yes |
| Impact | We computed for the first time triple frustrated ionization where two electrons escape and one electron stays in a highly excited Rydberg state during the break-up of the triatomic molecule H_{2}He^{+} |
| Title | Semiclassical tool and method to account for non-dipole effects in strongly-driven molecules |
| Description | The last few months we have developed a new theoretical and computational tool to account for magnetic field effects in molecules driven by intense laser fields. This new tool will have big impact in the attoscience and strong field community since almost all studies up to now do not include magnetic field effects. |
| Type Of Material | Computer model/algorithm |
| Year Produced | 2019 |
| Provided To Others? | No |
| Impact | This theoretical and computational tool we have developed in 2020, we will soon be published in an appropriate journal to effectively disseminate the results. We will use this technique to perform ground-breaking studies of magnetic field effects during the break-up of strongly-driven diatomic and triatomic molecules. |
| Title | Semiclassical tool for accounting for non-dipole effects in atoms |
| Description | We have developed a 3-d model for studying the effect of magnetic fields in strongly driven atoms |
| Type Of Material | Computer model/algorithm |
| Year Produced | 2017 |
| Provided To Others? | Yes |
| Impact | We have identified a new non-dipole effect, namely, non-dipole re-collision gated ionization |
| Title | Semiclassical toolkit for traitomic molecules |
| Description | We have developed a novel semiclassical 3-dimensional model that fully accounts for the break-up of strongly driven three center molecules. Using this model one can describe double ionization, frustrated double and frustrated single ionization in triatomic molecules. |
| Type Of Material | Computer model/algorithm |
| Year Produced | 2016 |
| Provided To Others? | Yes |
| Impact | We have produced already three papers on strongly-driven triatomic molecules in 2016 and 2017. |
| Description | LMU Munich |
| Organisation | Ludwig Maximilian University of Munich (LMU Munich) |
| Country | Germany |
| Sector | Academic/University |
| PI Contribution | We provided the theory for non-sequential double ionization of Ar for a range of intensities triggered by near-single cycle pulses. This collaboration resulted in 1 publication. In addition, we have collaborated on identifying a new mechanism of non-sequential double ionization for low intensities. Mainly we have identified the slingshot non-sequential double ionization, where two electrons escape opposite to each other. The main reason for the anti-correlation pattern is that one electron undergoes a slingshot motion around the nucleus as is the case in the gravitational slingshot motion of a spacecraft. The nucleus assists the electron in escaping in conjunction to the laser field. That is the change in momentum is in the same direction as the force from the field thus resulting in the electron absorbing the energy needed to escape. |
| Collaborator Contribution | The group of Prof. M. F. Kling provided the experimental results for the above project. Moreover, in the second project Prof. M. Kling and B. Bergues contributed to formulating the new mechanism of non-sequential double ionization. |
| Impact | This collaboration resulted in a very accurate theoretical description of the ultra-fast phenomena underlying non-sequential double ionization in atoms triggered by ultra-short laser pulses and the theory we provided explained very well the experimental results of Prof. M. F. Kling. Moreover, this collaboration resulted in identifying and formulating a new mechanism in strong field physics, namely, slingshot non-sequential double ionization which is the analog of the gravitational slingshot motion in strong field physics. |
| Start Year | 2017 |
| Description | National Research Council in Ottawa and University of Ottawa |
| Organisation | National Research Council - Ottawa |
| Country | Canada |
| Sector | Public |
| PI Contribution | My team was the main contributor in a collaboration with experimentalist Prof. P. B Corkum that resulted to the identification of a new non-dipole effect in non-sequential double ionization of strongly-driven He, namely, to non-dipole re-collision gated ionization In 2018, we collaborated with the group of Prof. Paul Corkum and Dr. Andre Staudte to control double ionization of Ar. To do so, we employed two-colour laser fields, one at 800 nm and the other at 2400 nm. |
| Collaborator Contribution | Prof. P. B. Corkum discussed with me the signatures of non-dipole effects in single ionization of atoms which his attoscience experimental group has identified in 2011, and then we were then able to investigate new effects in double ionization of atoms. In 2019, my experimental collaborators have provided the experiments for strongly-driven Ar by two-colour laser fields, while my group has provided the theory. The work from this latter project has resulted in a publication where we identify how to streak the ionization times of two electrons in double ionization when Ar is strongly driven by a two-colour laser field. |
| Impact | This collaboration has resulted in the identification of a new non-dipole effect and the publication of two journal papers. The collaboration is multi-disciplinary in the sense that Prof. Corkum is an experimentalist in the field of attoscience and my group is a theoretical and computational group in attosecond and strong-field science. Our joint work in 2018,. will result in an experimental scheme of identifying the ionization time of electrons in non-sequential double ionization of atoms driven by intense fields. |
| Start Year | 2008 |
| Description | An international conference taking place at University College London July 2-4 2018, "Atto-FEL 2018" |
| 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 | This is an international conference with 27 invited speakers including world leaders in the field of attosecond science. The speakers and attendees are from all over the world. This conference aims to bring together theorists from the FEL and Attosecond-Strong Field Science communities to discuss and present recent advances in theoretical techniques developed to tackle multi-electron effects in ionization of atoms and molecules. Another goal of this meeting is to draw together theorists and experimentalists in order to identify the most interesting challenges that both communities will face in the future. |
| Year(s) Of Engagement Activity | 2018 |
| URL | https://eventbooking.stfc.ac.uk/news-events/afels-2018 |
| Description | Deliver invited talks at the seminar series of the JASLab of the Attoscience Group at the National Research Council in Ottawa and the University of Ottawa |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | International |
| Primary Audience | Postgraduate students |
| Results and Impact | I delivered a talk on the semi-classical activities in my group on atoms and molecules driven by intense laser fields to the seminar series of the JASLab in Ottawa with an audience of Professors, senior researchers, graduate students and postdocs. |
| Year(s) Of Engagement Activity | 2021 |
| Description | Seminar Series : Frontiers of Ultafast Science UK |
| Form Of Engagement Activity | Participation in an activity, workshop or similar |
| Part Of Official Scheme? | No |
| Geographic Reach | National |
| Primary Audience | Other audiences |
| Results and Impact | Starting in 2017, I have initiated a seminar series "Frontiers of Ultafast Science UK". This seminar series takes place in different Institutions and Universities across the UK. Up to now I have organised 5 such seminars up to now. The goal is to bring together scientists working in different ultrafast-science fields such as, atomic and molecular physics, condensed matter physics, quantum optics, ultrafast chemistry and so on. |
| Year(s) Of Engagement Activity | 2017,2018,2019,2020 |