AMO

Posts related to atomic and molecular optics research

Physics alumnus Prof. Douglas Goodman and Professor Emeritus Winthrop Smith Featured in Online Peer Review Journal

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Prof. Emeritus Winthrop Smith and former student Prof. Douglas Goodman (Quinnipiac University) Edit Special Issue of Open Access Journal Atoms, on Low Energy Interactions between Ions and Ultracold Atoms

 The Special Issue of the online journal Atoms is a collection of current peer-reviewed articles by experts in the field of ultracold collisions and reactions involving ions and atoms co-trapped by electromagnetic fields in a common volume (a hybrid ion-neutral trap). Prof. Goodman, a recent UConn Ph.D. student of Prof. Smith (2015) who worked with hybrid traps for his dissertation, is now on the faculty of Quinnipiac University in Hamden, CT.

Prof. Smith’s research, on which he supervised four doctoral dissertations over the last few years, centers around the study of low-energy ion-neutral collisions. At long range, universal types of charge-induced polarization effects produce very large elastic, inelastic, reactive, and charge-transfer cross-sections leading to a high interaction probability between ions and neutral atoms at low temperature. The Special Issue articles highlight recent experimental and simulation work in this field and discuss the outlook for future developments.

Two of the manuscripts in this Special Issue explore recent advances in hybrid trap technology. The paper by Prof. Karpa explains the use of bichromatic optical dipole traps, which can be used instead of the previously developed hybrid rf ion trap and magneto-optic trap. This remarkable new technique avoids the use of rf fields and associated micromotion heating limitations and allows access to the long-sought quantum-dominated regime of interaction.

Karpa, L. Interactions of Ions and Ultracold Neutral Atom Ensembles inComposite Optical Dipole Traps: Developments and Perspectives. Atoms2021, 9(3), 39; https://doi.org/10.3390/atoms9030039 The manuscript included by Prof. Denschlag’s team, early practitioners of hybrid-trap ion-neutral studies, introduces a novel type of low-energy reaction. Denschlag’s group discusses the interaction between an atomic ion and an atom with a valence electron in a highly excited Rydberg state that reacts to yield a long-range atom-ion Rydberg molecule, with binding lengths up to the micrometer scale.Deiß, M.; Haze, S.; Hecker Denschlag, J. Long-Range Atom–Ion RydbergMolecule: A Novel Molecular Binding Mechanism. Atoms 2021, 9(2), 34;https://doi.org/10.3390/atoms9020034 https://www.mdpi.com/2218-2004/9/2/34

The remaining two manuscripts in this Special Issue address important phenomenology of rf Paul traps as they are used in ion-neutral interaction experiments. The paper by Prof. Blumel analyzes the properties of ion clouds loaded from a magneto-optical trap in a hybrid ion-neutral system. He develops theoretical predictions for optimal loading conditions for hybrid-trap experiments, which are supported by numerical simulations. Additionally, he predicts the existence of a new type of ion heating mechanism caused by the increase in Coulomb energy associated with each newly loaded ion within the existing ion-cloud volume.

Blümel, R. Loading a Paul Trap: Densities, Capacities, and Scaling inthe Saturation Regime. Atoms 2021, 9(1), 11; https://doi.org/10.3390/atoms9010011https://www.mdpi.com/2218-2004/9/1/11

Last, the manuscript by Prof. Rangwala’s group, numerically and analytically explores the benefits of using linear multipole rf traps for studying low-energy ion-neutral collisions, as opposed to the conventional quadrupole ion-trap configuration. Using new analyses of the heating effects, Rangwala’s group shows that the higher-order multipolar trap configurations reduce unwanted heating in the ion-neutral system. In doing so, they develop a methodology for comparing and optimizing hybrid trap designs.

Niranjan, M.; Prakash, A.; Rangwala, S. Analysis of Multipolar Linear

Paul Traps for Ion–Atom Ultracold Collision Experiments. Atoms 2021,

9(3), 38; https://www.mdpi.com/2218-2004/9/3/38

https://doi.org/10.3390/atoms9030038

New Faculty Hire-Dr. Anh-Thu Le

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The Physics Department welcomes our newest faculty member, Dr. Anh-Thu Le, although he prefers to be called simply AT. AT worked for many years at the well-known James R. Macdonald Laboratory, rising to the rank of Research Professor. He worked alongside a world-known theorist, Dr. Chii-Dong Lin. Dr. Le went on to become an Assistant Professor at Missouri University of Science and Technology before coming to UConn. Dr. Le is well-versed in current theoretical methods for exploring the interaction of ultrafast lasers with atoms and molecules. He has a strong overlap with the ultrafast AMO experimental programs at UConn and has collaborated with high-profile experimental groups.

Dr. Le has a thoroughly international and diverse background, having grown up in the Vietnamese countryside. His research career has taken him from Vietnam to the Republic of Belarus, Germany, Canada, and ultimately the US. This has left him with a lasting commitment to serving diverse populations, both in the classroom and in his research.

Professor Nora Berrah Awarded a Blaise Pascal Chaire d’Excellence to Conduct Research in France

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Professor of Physics Nora Berrah has been awarded the International Blaise Pascal Chaire d’Excellence, a prestigious honor whose previous winners include scientists and scholars from a wide range of disciplines, including multiple Nobel laureates. Her award was selected by a committee of scientists and voted on by the Permanent Commission Regional Council of the Région Île-de-France.

Prof. Berrah in her lab
Prof. Berrah in her laboratory.

This award is bestowed to scientists of international reputation who are invited to conduct research in the Paris area. The goal is to establish international collaborations and exchange, as well as share science globally. In Berrah’s case, the collaboration is between UConn and the Commissariat à l’énergie atomique et aux énergies alternatives de Saclay (CEA, Paris Saclay). The collaborative work is aimed to push the frontiers of science, as well as enrich and facilitate international research.

The Région Île-de-France selects every year four  laureates of high international standing in their field of expertise. All research areas are included, such as the humanities, arts, and sciences, in the selection of the awardees. Six Nobel laureates have been selected for the award since 1996. Prof. Berrah was selected by the Blaise Pascal Chaire Committee for the field of Fundamental Physics.

For more information about Professor Berrah’ award, see the article in UConn Today

Radiation Damage Spreads

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Radiation Damage Spreads Among Close Neighbors

X-ray absorption cascade
Direct hit. A soft x-ray (white) hits a holmium atom (green). A photo-electron zooms off the holmium atom, which releases energy (purple) that jumps to the 80-carbon fullerene cage surrounding the holmium. The cage then also loses an electron. (Courtesy of Razib Obaid)

March 17, 2020 – Kim Krieger – UConn Communications

A single x-ray can unravel an enormous molecule, physicists report in the March 17 issue of Physical Review Letters. Their findings could lead to safer medical imaging and a more nuanced understanding of the electronics of heavy metals.

Medical imaging techniques such as MRIs use heavy metals from the bottom of the periodic table as “dyes” to make certain tissues easier to see. But these metals, called lanthanides, are toxic. To protect the person getting the MRI, some chemists wrap the lanthanide inside a cage of carbon atoms.

Molecular physicist Razib Obaid and his mentor, Prof. Nora Berrah in the physics department, wanted to know more about how the lanthanides interact with the carbon cages they’re wrapped in. The cages, 80 carbon atoms strong, are called fullerenes and are shaped like soccer balls. They don’t actually bond to the lanthanide; the metal floats inside the cage. There are many similar situations in nature. Proteins, for example, often have a metal hanging out close to a giant organic (that is, mostly made of carbon) molecule.

So Obaid and his team of collaborators from Kansas State University, Pulse Institute at Stanford, Max Planck Institute at Heidelberg, and the University of Heidelberg studied how three atoms of the lanthanide element holmium inside of an 80-carbon fullerene reacted to x-rays. Their initial guess was that when an x-ray first hit one of the holmium atoms, it would get absorbed by an electron. But that electron would be so energized by the absorbed x-ray that  it would fly right out of the atom, leaving a vacant spot. That spot would than get taken by another of the holmium’s electrons, which would have to jump down from the outer edge of the atom to fill it. That electron had formerly been partnered with another electron on the outskirts of the atom. When it jumped down, its lonely ex, called an Auger electron, would zoom away from the whole molecule and get detected by the scientists.  Its distinctive energy would give it away. 

It sounds complicated, but that would have been the simplest (and thus most likely) scenario, the physicists thought. But it’s not what they saw.

When Obaid and his colleagues zapped the holmium-fullerene molecule with a soft x-ray (about 160 electron-volts), the number of the Auger electrons detected was too low. And too many of the electrons had energies much less than the Auger electrons should have. 

After some calculating, the team figured out there was more going on than they’d guessed.

First, the x-ray would hit the holmium, which would lose an electron. The vacant spot would then be filled by the outer edge electron from the holmium atom. That much was correct. But the energy released by the jumping electron (when it jumps ‘down’ from the outskirts of the atom to the interior, it also jumps ‘down’ in energy) would then be absorbed by the carbon fullerene cage or another of the neighboring holmium atoms. In either case, the energy would cause an additional electron to zoom away from whatever absorbed it, the fullerene cage or the holmium atom.

Losing these multiple electrons destabilized the whole molecule, which would then fall apart entirely.

The end result?

“You can induce radiation damage just by striking one atom out of 84,” says Obaid. That is, a single x-ray strike is  enough to destroy the entire molecule complex through this energy transfer process involving neighboring atoms. It gives some insight into how radiation damage occurs in living systems, Obaid says. It was always thought that radiation damaged tissue by stripping away electrons directly. This experiment shows that interactions between an ionized atom or molecule and its neighbors can cause even more damage and decay than the original irradiation.

The work also gives medical physicists an idea of how to limit patient’s exposure to heavy metals used as dyes in medical imaging. Shielding all parts of the body from the radiation except for those to be imaged with heavy metal dyes can potentially restrict the heavy metal exposure as well as the radiation damage, the researchers say. The next step of this work would be to understand exactly how fast this interaction with the neighbors occurs. The researchers expect it to take place in just a few femtoseconds (10-15 s). 

The work was funded by Department of Energy, Basic Energy Sciences (BES), Division of Chemical Sciences, Geosciences, and Biosciences, under Grant No. DE-SC0012376.

Daniel McCarron wins NSF Early Career Award

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Daniel McCarron, assistant professor of physics, the College of Liberal Arts and Sciences, will receive $645,000 over five years for his work on the development of techniques to trap large groups of molecules and cool them to temperatures near absolute zero. The possible control of molecules at this low temperature provides access to new research applications, such as quantum computers that can leverage the laws of quantum mechanics to outperform classical computers.

The NSF Faculty Early Career Development (CAREER) Program supports early-career faculty who have the potential to serve as academic role models in research and education, and to lead advances in the mission of their department or organization. Activities pursued by early-career faculty build a firm foundation for a lifetime of leadership in integrating education and research.

McCarron was one of 8 junior faculty at the University of Connecticut to receive the prestigious Early Career awards from NSF in 2019. For a description of all 8 awards, see this recent article published in UConn Today.

Meet the Researcher: Carlos Trallero

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August 19, 2019 – Anna Zarra Aldrich ’20 (CLAS), Office of the Vice President for Research

When Carlos Trallero started his academic career in physics, he had no idea he would become a pioneer in a field of research that uses high-power lasers to investigate atomic and molecular physical phenomena.

Originally from Cuba, where there isn’t much funding for experimental research, Trallero began his academic career by studying theoretical physics. But as a senior graduate student at Stony Brook University, he got the chance to work in a lab doing experimental work and quickly recognized it was his true passion.

“I talked to a professor doing experimentation with ultra-fast lasers and I fell in love with it. And at first, I sucked at it — I was horrible,” says the professor of physics who is now working with four research grants funding separate investigations.

Trallero works with very short laser beams, with an emphasis on very short. The lasers he uses can pulse with attosecond precision. As a comparison, there are as many attoseconds in one second as there have been seconds in the entire history of the universe since the Big Bang.

It takes light half an attosecond to cross the orbit of hydrogen, the smallest atom. When trying to study something that fast, scientists need the kind of precision the lasers Trallero can offer. The goal of this research is to gain a better understanding of how electrons, one of the fundamental atomic building blocks in the universe, move and react to light. By understanding the physics of electron movement, scientists could improve the design of technologies like superconductors.

“The dream is to be able to perform logistical operations like a computer at the attosecond level,” Trallero says. “It would really advance computational speeds. If you could make as many calculations in a second as there have been seconds in the history of the universe – that’s an astounding number.”

His lab is now working to break the attosecond barrier into the zeptosecond barrier which is 1,000 times faster than the attosecond.

While some of the potential applications of this research remain unknown since the field is still in its infancy, Trallero views the premise of his research as creating basic knowledge. He is investigating the atomic and molecular phenomena which determine so many things in our universe but about which we still know relatively little.

Members of Trallero’s lab from left to right, Edward McManus, Michael Davino, Carlos Trallero, Brandin Davis, Zhanna Rodnova, Tobias Saule, Rich Sadlon. (Carson Stifel (’21 CLAS)/UConn Photo)

One project funded by the Department of Energy has Trallero looking at the properties of atoms and molecules in the quantum world by harnessing light waveforms at the attosecond time scale through interferometry. Interferometers provide precise measurements of molecules using two beams of light which interfere with each other. The images produced by this technology will allow Trallero to find out information about the rotational dynamics of molecules.

“In the quantum world, properties of atoms and molecules are not as simple as in the real world,” says Trallero.

Another of Trallero’s grants, from the U.S. Air Force Office of Scientific Research, involves creating an incredibly bright beam. Trallero’s lab is working on taking electrons out of nanoparticles and then sending them back in, which will produce a bright, energetic light. “The process to study these dynamics has never been executed in this manner,” Trallero says.

Trallero is also working on two grants from the U.S. Navy,  including one that aims to develop infrared “body heat lasers.”

Through these grants, Trallero is developing a new class of laser which is only comparable to those found at large, multinational laser facilities like the European Light Infrastructure. Compared to the technology currently available to Trallero at UConn, this new class of laser will have almost 20 times more average power than the current laser.

Developing a laser of this caliber will be incredibly useful for studying phenomena that only occur a few times per shot of the laser in real time. The laser will enable researchers to probe the molecules with X-rays and ultraviolet rays to look at their structure and is being developed through a partnership with a Canadian company, Few-cycle, and a German company, Amphos. Researchers like Trallero are able to get advanced technology for a fraction of their retail value by doing research of interest for these companies, which are constantly trying to innovate in step with the science.

“We’re only paying a fraction of the price because the company is interested in showing they can develop this kind of technology,” Trallero says. “Showing they have the capacity and showcasing what we do with, and for, them helps them gain a customer base and it helps us make major advances in basic science at the same time.”

Trallero is also considering creating spin-off tech companies based on his university inventions with graduate students and postdocs. He has developed nanoparticle technology which can help transform molecules from a liquid to a gaseous state which could be beneficial for producing aerosols.

Trallero views physics as “the broadest science” since it has unique applications to math, engineering, chemistry and, even, biology. “I try to think about particular scientific questions in a different way than perhaps other people who have been working in this field for a long time do,” Trallero says. “Often we suffer from too much in-depth specialization.”

He wants to make use of the tools from every specialty he can, and he instills this same inclination in the students working in his lab.

“They don’t know what they’re going to face in the future and by having a broad skill set and a broad mindset they’ll be prepared for anything,” Trallero says. “You’re opening your mind to more possibilities.”

This article first appeared on UConn Today, August 19, 2019

2019 Pollack Lecture

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On April 11th and 12 of 2019 Prof. Paul Corkum of the Joint Attosecond Laboratory (University of Ottawa and the National Research Council of Canada) visited the department. Prof. Corkum’s main area of research is on the interaction of ultrashort laser pulses with matter broadly defined. His most notable contribution is perhaps the discovery of the so-called three-step model, which has become the basis of the emerging field of attosecond science. Attoseconds, equal to 1 billionth of 1 billionth of a second (10-18 s) is the shortest time scale ever measured or controlled by humans and is at the forefront of modern optics.

Prof. Corkum is a member of the US National Academy of Sciences, the Russian Academy of Sciences, the Austrian Academy of Sciences, the Royal Canadian Academy of Sciences and the Royal Society of London. He has received many accolades throughout his career, including the Thomson Reuters Citation Laureate which is awarded to researchers who are “of Nobel class” and likely to earn the Nobel someday and the Order of Canada.

On April 12, Prof. Corkum presented the annual Edward Pollack Distinguished Lecture, entitled “Attosecond Pulses Generated in Gases and Solids”. This lecture is supported by an endowment established by the family of the late Professor Edward Pollack in 2005. Ed’s family, friends and colleagues made contributions in his memory. This special colloquium provides a presentation in Ed’s honor in the field of atomic, molecular and optical physics, his area of research expertise. This year Mrs. Rita Pollack and their three children: Cindy [U.S. Government civil servant], Lois [now a professor of applied physics at Cornell], and Howard [professor of modern languages (German) at dePauw University in Indiana] were all in attendance.

Below, dinner with the Pollack family members, UConn faculty, and guests.

Clockwise from left: Victoria Starzef, George Gibson, Win Smith, Anne Smith, Margaret Kessel, Quentin Kessel, Nadia Corkum, Paul Corkum, Robin Côté, Lois Pollack, Cindy Blazar, Rita Pollack, Howard Pollack-Milgate, Sophie Pollack-Milgate, and Sarah Trallero

 

2 for the price of 1: UConn researcher finds new mechanism making double ionization an efficient process

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Schematic of dICD

An international research team headed by Dr. Aaron LaForge from the research group of Prof. Nora Berrah in the Physics department at UConn has recently discovered a new type of decay mechanism leading to highly efficient double ionization in weakly-bound systems. The team has published its results in the science journal “Nature Physics”.

Ionization is a fundamental process where energetic photons or particles strip an electron from an atom or molecule. Normally, a much weaker process is double ionization, where two electrons are simultaneously emitted, since it requires higher-order interactions such as electron correlation. However, these new results show that double ionization doesn’t necessarily need to be a minor effect and can even be the primary ionization mechanism thereby getting two electrons for the price of one.

The enhancement is likely due to double ionization proceeding through a new type of energy transfer process termed double intermolecular Coulombic decay, or dICD, for short. The experiments were performed at the synchrotron, Elettra, in Trieste, Italy. There, electrons are accelerated to near the speed of light and then rapidly undulated through an alternating magnet field. In this way, the electrons emit short wavelength light which is needed to trigger dICD. The researchers produced superfluid helium droplets, which are cryogenic, nanometer-sized matrices capable of attaching various atomic and molecular species in order to perform precise spectroscopic measurements. In this case, dimers consisting of two alkali metal atoms were attached to the surface of helium droplets. The dICD process, schematically shown in Fig. 1, occurs through an electronically excited helium atom (red), produced by the synchrotron radiation, interacting with the neighboring alkali dimer (blue and white) resulting in energy transfer and double ionization. Although an alkali dimer attached to a helium nanodroplet is a model case, dICD is potentially relevant for any system where it is energetically allowed.

dICD belongs to a special class of decay mechanisms where energy is exchanged between neighboring atoms or molecules leading to enhanced ionization rates. Seemingly ubiquitous in weakly-bound, condensed phase systems such as van der Waals clusters or hydrogen-bonded networks like water, these processes can contribute to radiation damage of biological systems by producing particularly harmful low-energy electrons. dICD could strongly enhance such effects through the production of two low-energy electrons for each intermolecular decay.

Original publication:

A. C. LaForge, M. Shcherbinin, F. Stienkemeier, R. Richter, R. Moshammer, T. Pfeifer & M. Mudrich, “Highly efficient double ionization of mixed alkali dimers by intermolecular Coulombic decay”, Nature Physics (2019) DOI: 10.1038/s41567-018-0376-5

Nora Berrah Named 2018 AAAS Fellow

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Physics professor Nora Berrah has been named a 2018 Fellow of the American Association for the Advancement of Science (AAAS). Prof. Berrah has been recognized for her distinguished contributions to the field of molecular dynamics, particularly for pioneering non-linear science using x-ray lasers and spectroscopy using synchrotron light sources.

Prof. Berrah

View full story on CLAS website.

Prof. C. Trallero awarded multiple research grants

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Anna Zarra Aldrich, Office of the Vice President for Research
(Photo: Trallero Lab/Kansas State Photo)

University of Connecticut physics professor Carlos Trallero has been granted $1.06 million from the Department of Defense, the U.S. Air Force and the Air Force Office of Scientific Research to study recollision physics at the nanoscale to help develop ultrafast electronics.

This research will enhance the knowledge base of electron recollision dynamics at the nanoscale, which can be used to develop ultrafast light-driven electronics. These applications may be made possible by cultivating an improved understanding of the interactions and knowledge of the time scales of light-induced electronic motion including collective plasmonic excitations.

Trallero and co-PIs from Kansas State University will study the response of individual gas-phase nanoparticles to intense femtosecond (10-15 seconds) laser fields using high-harmonics spectroscopy, momentum-resolved photoelectron imaging and corresponding theoretical modeling.

Earlier research on photoelectron emission from dielectric and metal nanoparticles has demonstrated that nanoparticles may be a promising system for exploiting the effects of laser-induced electron recollision due to the interplay between the laser field and the near-field of the particle.

By extending these studies to longer wavelengths (400 to 9000 nanometers) and complementing them with high-harmonic generation from nanoparticles and nanoparticle aggregates, Trallero and his team will help build a better knowledge base of electron recollision dynamics at the nanoscale.

“We predict that through this study, we will identify behaviors on the nanoscale that will differ significantly from those that have been studied at the atomic level,” said Trallero.

The UConn-led team will work on the possibilities of controlling the nanoparticle response, especially plasmonic excitations, by applying synthesized two-color fields. They will also explore harmonic generation from tailor-made nanoparticles as a potential source of intense, short-pulsed XUV light.

By generating harmonics from fractal aggregates and supper-lattices of nanoparticles, Trallero will gather information on the transition from localized molecule-like to de-localized solid-like electron-field interactions. The team also plans to study plasmonic excitations in laser pump, X-ray probe experiments using time-resolved soft X-ray scattering.

In collaboration with ultrafast physics faculty, Professors George Gibson and Nora Berrah, Trallero has started planning and building an “Ultrafast Center,” with ties to industry for research that includes an interdisciplinary group of faculty from the department of physics, the Institute of Materials Science,  and the Schools of Engineering and Pharmacy. These faculty are specialized in optics, atomic and molecular physics, condensed matter, material science and engineering.

Carlos Trallero, who received his PhD in physics from Stony Brook University in 2007, joined UConn in 2017. His research focuses on attosecond science, strong field molecular spectroscopy, cohere control, higher-order harmonic generation, non-Gaussian optics, strong field science at long wavelengths and ultrafast optics.

This research is funding under DOD project number FA9550-17-1-0369.