Nadia Fomin Elected APS Fellow

October 13, 2026

Professor Nadia Fomin calls her path to success “untraditional.” The latest stop on that journey is election as a Fellow of the American Physical Society (APS), making her the 11th member of UT’s current physics faculty to win the honor.

APS recognized Fomin “for extensive studies of short-range correlations in nuclei and their impact on the in-medium structure of the nucleon, critical contributions to a broad program of hadronic weak interaction experiments, and a remarkable record of leadership and mentoring.”

Professor and Department Head Adrian Del Maestro explained how Fomin’s contributions strengthen the university’s research and educational goals.

“This well-deserved honor for Professor Fomin recognizes the remarkable achievements she has made, which connect the University of Tennessee with world-leading facilities at Oak Ridge and Jefferson National Laboratory,” he said. “Her extensive mentorship track record has provided unique educational and research experience for our students and this fellowship places her amongst an elite group of physicists in Knoxville.”

Nucleons in Close Quarters

Every atom is governed by a nucleus made up of particles called nucleons (protons and neutrons). Held together by the strong force, how they interact at very short distances in bound nuclei can show scientists how the intricate structure evolves and what that means for a specific nucleus.

“Those can be interactions of the substructure, the nucleons,” Fomin said, “but also their substructure, quarks, and how that behavior is modified by the fact that the proton or neutron is inside the nuclear medium. If it’s a neutron or a proton in carbon versus one in gold, you might see different things.”

This goes to the heart of quantum chromodynamics (QCD), the fundamental theory describing how the strong force builds on the substructure of a nucleus to form larger particles.

“Underlying quantum chromodynamics is one of the earliest stages in how collective behavior emerges from the substructure,” Fomin explained, giving scientists a deeper understanding of matter.

The research is based at Jefferson Lab in Virginia, though Fomin also plays a key role in experiments using neutrons from Oak Ridge National Laboratory’s Spallation Neutron Source. The current program aims to probe physics beyond the Standard Model via studies of neutron beta decay. Along with her campus laboratory, this broad program gives her 12 research students (undergraduate and graduate) opportunities to work at UT or national laboratories.

An Untraditional Path to Success

Fomin first came to UT as a postdoctoral associate working with Geoff Greene (now professor emeritus). She joined the faculty in 2013 and estimates that she’s mentored 50 students, as well as junior faculty.

She and colleague Shelly Lesher won a grant to lead a mentoring workshop for early career faculty at the APS Division of Nuclear Physics meeting. (UT Assistant Professor Dien Nguyen, a Department of Energy Early Career Award winner, is a past participant.)

Fomin draws on her own experience to show younger scientists there’s no single way to achieve success as a physicist. After graduating from Georgetown University with a bachelor’s degree in physics and computer science, she said, “I took a year and a half off. I worked. I didn’t know what I wanted to do.”

She decided to leave her job as a software engineer and enrolled as a physics graduate student at the University of Virginia, though she didn’t intentionally choose nuclear physics as a focus.

“I didn’t know how it worked,” she said. “I didn’t know that you do research over the summer. I thought I had to get a summer job.”

When other students talked about labs where they worked she didn’t understand what they meant. A classmate encouraged Fomin to join a nuclear physics group that had solid funding, so she chose that route out of pragmatism.

“That’s how I ended up in nuclear physics,” she said. “It was not a permanent commitment. It was just for the summer. But I liked it.”

Fomin shares that story with students in her Picture a Physicist Seminar (Physics 211) to give them a clear picture of what graduate school is like. She said she tells them things that no one told her so they can make more informed choices. She sees these personal examples as an important part of being a professor.

“I think (it shows) both our graduate students and undergrads that success can be fairly untraditional,” she explained.

Mentorship plays a central role in Fomin’s work. Physics students have awarded her the department’s Research Advisor of the Year Award three times over the past five years. The APS Fellowship is also her second Society honor in five years: the Southeastern Section of APS presented her with the Francis G. Slack Award in 2021 for her service to physics in the Southeast.

Fomin will receive her official APS Fellowship award at the APS Division of Nuclear Physics meeting this week in Philadelphia. Fellows are selected based on exceptional research, innovative contributions in applying physics to science and technology, advancements in teaching, and exemplary service to the Society. The number of recommended nominees each year may not exceed one-half percent of the then-current APS membership.

“I really enjoy the feeling of being appreciated by the community,” Fomin said. “Not just recognized, but appreciated.”

Research Rock Stars: Thomas Papenbrock Explores the Forces at the Core of Matter

June 23, 2026

Rules for Nuclear Couples

June 10, 2026

Atoms are governed by nuclei and nuclei have rules of their own. Physicists like Assistant Professor Dien Nguyen study those rules. In a just-published Nature paper, she and colleagues report on a new quantum selection process that could impact how scientists understand nuclear structure, which plays a major role in fields like medicine and energy.

How Particles Pick Partners

A nucleus is a quantum system made up of protons and neutrons (nucleons), held together by the strong nuclear force. At very short distances, those nucleons can double up momentarily into short-range correlated (SRC) pairs.

“SRC pairs play an important role in helping us understand how protons and neutrons interact at very short distances inside the nucleus,” Nguyen explained. “This nucleon-nucleon interaction is what binds protons and neutrons together and determines many properties of the nucleus.”

To find out how these partnerships form, she and the research team scattered electrons from calcium (Ca-40 and Ca-48) and iron (Fe-54) targets at the Thomas Jefferson National Accelerator Facility, detecting both scattered electrons and knocked-out protons. Nguyen said the three nuclei chosen were a special collection based on how their protons and neutrons are arranged in discrete energy levels, or “shells.”

“Calcium-40 and calcium-48 have the same number of protons, but calcium-48 has eight additional neutrons in an outer shell,” she said. “Calcium-48 and iron-54 have the same number of neutrons, but iron-54 has six additional protons in the same outer shell. This comparison allowed us to separate the effect of adding neutrons from the effect of adding protons in a specific shell.”

The six additional protons in iron translated into some surprising results.

Nguyen explained that adding eight neutrons (40 percent) in calcium-48 resulted in only about 10 percent more SRC proton pairs over calcium-40. Adding six protons (30 percent) in iron-54, however, led to about 50 percent more SRC proton pairing compared to calcium-48. She said the results show that pair formation isn’t controlled simply by the total number of protons or neutrons.

“Instead, it depends strongly on the quantum orbitals that the protons and neutrons occupy,” she said. “In other words, nucleons are much more likely to form SRC pairs when their quantum states are favorable.”

She added that the results point to a new kind of quantum selection rule governing how nucleons can pair at short distances.

“It was not known before and could have an important impact on how we understand nuclear structure, especially how protons and neutrons interact and organize themselves inside the nucleus,” Nguyen explained.

Meaning in Every Achievement

Nguyen is the first author on the Nature paper and worked with the CaFe team (as they call themselves) to lead the project. They took the first data in late August 2022, when she was a Nathan Isgur Fellow at Jefferson Lab and a week away from delivering her daughter. A good friend and fellow CaFe member had a two-month-old baby at the time, and Nguyen said the two young moms made a pact.

“We said to each other ‘Let’s get the first paper out before our kids turn four,’” she said. “And we did it: we kept our promise with our babies.”

(For Nguyen there was an additional bonus: her husband promised her an upscale “CaFe” machine for morning coffee if they published in Nature, which he’s made good on.)

She is quick to acknowledge the research success is shared among the entire CaFe team, Jefferson Lab’s Hall C collaboration, including physics graduate and paper co-author Casey Morean (PhD, ’23).

“I am truly grateful to everyone who helped bring the project to this point,” Nguyen said.

Publishing in Nature is the latest in a string of successes she’s earned since joining the physics faculty in 2024. In 2025 she won a U.S. Department of Energy Early Career Award to support her research on how spin shapes the fundamental structure of matter. In 2026 she was recognized with the UT College of Arts and Sciences Excellence in Research and Creative Achievement Award (Early Career). She’s also deeply invested in helping her students succeed and has been voted the department’s Research Advisor of the Year by both the graduate students (2025) and the undergraduate physics majors (2026).

“For me, professional life is my passion and it always goes along with my personal life and with my loved ones,” she said. “So (the) personal part is meaningful to me (in) every achievement.”

Measuring What Comes Before Alpha

May 27, 2026

University of Tennessee physicists and their colleagues have made critical measurements of the lifetime and decay energy of tellurium-104 (Te-104), an important step in answering a century-old question and understanding how hundreds of nuclei decay. The results are published in Nature.

A Particle Determined to Escape

Professor Robert Grzywacz led the experimental team at the Radioactive Isotope Beam Factory (RIBF) at RIKEN in Japan. He explained how the results match decades-old predictions that tellurium-104 is a special case in alpha decay, a process where an alpha particle (a strongly-bound system of two protons and two neutrons) tunnels through the barrier surrounding the nucleus where it resides. Though alpha radioactivity was discovered more than 125 years ago, where the particle comes from is still a mystery, especially in nuclei that have large numbers of protons and neutrons.

“Alpha decay is the oldest decay mode,” Grzywacz said. “The big question is how the alpha particle forms in heavy nuclei, which are known to have uniform matter distribution. There must be a mechanism which causes local ‘clump’ or ‘cluster’ formation.”

Clustering is connected to how a nucleus is structured. Called preformation, it’s a signal an alpha particle is about to make a break for it.

“Once formed,” Grzywacz explained, “the alpha particle will escape from the nucleus.”

He said that this emission is a well-understood quantum mechanical tunneling process that depends on available energy. Since the 1960s scientists have thought that one nucleus—tellurium-104—has a special enhancement that could better explain how it happens.

Following the Decay Chain

While tellurium lives among the metalloids on the periodic table and can be found in nature, the isotope tellurium-104 has to be synthesized. Creating these nuclei is a challenge for multiple reasons. First, they only live for a few nanoseconds. Second, they’re a result of the decay of xenon-108, which in itself is difficult to produce. In this experiment, the team overcame these still-formidable obstacles with technological advances at RIBF. Using four coupled cyclotrons, they accelerated a beam of xenon-124 into a beryllium target. The collision produced fragments of xenon-108, whose decay populates tellurium-104, which is followed in this decay chain by tin-100.

“We have measured the lifetime and energy of this decay and found that the preformation probability is much larger than expected based on predictions, which used available experimental knowledge,” Grzywacz said. “We also found that tellurium-104 is the shortest known alpha particle radioactive nucleus with a 7.2 nanosecond half-life. This very short half-life, corrected for decay energy, gives unusually high alpha particle preformation. It will likely be a single case like that among all nuclei.”

He added the only other case is the well-studied decay of polonium-212 to lead-208, which has preformation probability 10 times smaller than that of tellurium-104.

Grzywacz said that more than half a century ago scientists pictured tellurium-104 having a brief existence as a molecule comprising tin-100 and an alpha particle. Tin-100 is a doubly-magic nucleus, meaning it’s strongly bound, as is an alpha particle. He and the research team attribute tellurium-104’s high preformation to its relation to doubly-magic tin, creating favorable conditions to form an alpha particle.

A Trail Blazed at Oak Ridge

Years of previous studies made these findings possible. Much of that work was rooted at the U.S. Department of Energy’s Oak Ridge National Laboratory (ORNL), where researchers have been at the forefront of exploring the island of alpha-emitting nuclei near tin-100 for decades. In 2006, a team including Grzywacz and ORNL physicists Krzysztof Rykaczewski and Carl Gross used the Recoil Mass Spectrometer at ORNL’s historic Holifield Radioactive Ion Beam Facility (HRIBF) to discover the neighboring xenon-109 to tellurium-105 to tin-101 alpha-decay chain. The measurement suggested that alpha-particle preformation was growing as nuclei approached doubly-magic tin-100. This strengthens the case that tellurium-104 would be the definitive test of the “superallowed” prediction, where the parent nucleus is essentially the doubly-magic plus a preformed alpha particle.

Independently, a 2018 experiment at Argonne National Laboratory (ANL) achieved the first observation of the xenon-108 to tellurium-104 to tin-100 chain, though the two decays could not be fully separated, leaving the individual half-life and energy of tellurium-104 unmeasured. In parallel, the detector technology pioneered at Holifield—fast-response scintillator crystals coupled to position-sensitive photomultiplier tubes—was further developed by Grzywacz’s group and ORNL collaborators at Japan’s Advanced Science Research Center, and proved essential for the present RIKEN experiment.

Rykaczewski, a Distinguished Senior Researcher in ORNL’s Physics Division and co-spokesperson for the RIKEN experiment, played a central role in designing and executing the measurement. Toby King, a UT physics graduate now on ORNL’s staff, was instrumental in building and operating the detection system and data acquisition. Additional ORNL support came from James Allmond and Thomas Ruland, who provided supplemental equipment and on-site experimental assistance.

“The path from the Holifield discovery of the tellurium-105 decay chain to this definitive measurement of tellurium-104 spans nearly two decades of sustained effort between UT and ORNL,” Rykaczewski said. “Each step—new isotopes, new detectors, new accelerator capabilities—brought us closer to this singular nucleus.”

A Strong Foundation for Students

Ian Cox (PhD, 2024) was the paper’s lead author. Now a postdoctoral appointee with ANL, he began working on the project as an undergraduate physics major and handled most of the experimental analysis “in record time,” according to Grzywacz.

“Studying nuclei on the edge of existence presents significant challenges but can also produce profound results,” Cox said.  “It has been a pleasure to start my research career with a result that can greatly impact the field.”  

Following in his footsteps, current Graduate Students Nico Braukman and Donnie Hoskins (physics), as well as Benjamin Kreider (engineering) were all co-authors on the Nature publication.

“Getting exposure to the kind of work that goes into producing high-impact physics results is an important part of being a grad student,” Braukman said. “I’m glad to have had the opportunity to participate in this experiment early in my grad school career.”

Hoskins shared similar sentiments.

“As a graduate student, one of our goals is to learn and participate in research to prepare us for our futures,” he said. “Exposure in prestigious journals, like Nature, increases visibility for me as an independent scientist to set up my own research in the future with a proven strong foundation in nuclear physics.”

The experimental effort included UT Physics Research Assistant Professor Z.Y. Xu, along with partners from ORNL, RIKEN, the University of Tokyo, the University of Warsaw, the National Centre for Nuclear Research (Poland), the Universität zu Köln (Germany), Universidad Complutense de Madrid (Spain), Lawrence Livermore National Laboratory, and the Japan Atomic Energy Agency.

The U.S. Department of Energy Office of Science and the National Science Foundation helped support this work.

How Spin Shapes the World

January 15, 2026

One Experiment: Three Discoveries

October 13, 2025

You can’t have gold until a nucleus decays. The specifics of that process have been hard to pin down, but UT’s nuclear physicists have published three discoveries in one paper explaining key details. The results can help scientists come up with new models to describe the stellar processes that give us heavy elements, as well as make better predictions about the expanding landscape of exotic nuclei.

The Physics of Bling

Elements like gold and platinum are created under extreme conditions, like when stars collapse, explode, or collide. In the rapid neutron-capture process (or r-process for short), a nucleus captures a barrage of neutrons in quick succession until it becomes so heavy it decays into lighter, more stable nuclei. As it crosses the nuclide chart, the r-process path winds through territory where the main decay mode is beta decay of the parent nucleus, followed by the emission of two neutrons. The nuclei involved are difficult (if not impossible) to study experimentally, so the calculations describing them lean heavily on models that need to be validated in the lab.

To get a better picture of how all this happens, researchers including UT Graduate Students Peter Dyszel and Jacob Gouge, Professor Robert Grzywacz, Associate Professor Miguel Madurga, and Research Associate Monika Piersa-Silkowska worked with a host of scientists from other institutions. Building on data analysis methods outlined by Research Assistant Professor Zhengyu Xu, they started with large amounts of indium-134.

“These nuclei are hard to make and require a lot of new technology to synthesize in sufficient quantities,” Grzywacz explained.

The ISOLDE Decay Station at CERN met the challenge by providing plenty of indium-134 nuclei, as well as sophisticated laser separation technology to make sure they were pristine. When indium-134 decays, it populates excited states in tin-134, tin-133, and tin-132. Using a neutron detector funded by the National Science Foundation Major Research Instrumentation program and built at UT, scientists made three important discoveries. At the top of the list, they made the first measurement of neutron energies for beta-delayed two-neutron emission.

The two-neutron emission is the biggest deal,” Grzywacz said.

Beta-delayed two-neutron emission occurs only in exotic nuclei, those that are short lived and unstable. The two-neutron separation energy is very small, but in this experiment it was enough to be measured.

“The reason this is hard is because neutrons like to bounce around. It’s hard to tell if it’s one or two,” Grzywacz explained. In earlier attempts, “no one measured energies,” so this approach “opens a completely new field.”

This is the first study detailing the two-neutron emission for a nucleus that follows the r-process path, opening the door for clearer models about how stellar events can create elements like gold.

Tin Never Forgets

A second discovery was the first observation of a long-sought single-particle neutron state in tin-133. Grzywacz explained that “tin is in an excited state. (It) has to cool off. It can spit out a neutron, or, with enough energy, it can spit out two neutrons. It should always spit two neutrons, but it doesn’t.”

He said the traditional view is that tin “boils off” neutrons to cool down, becoming “an amnesiac nucleus,” with no memory of beta decay.

“We say the tin doesn’t forget,” Grzywacz said. “This ‘shadow’ of indium doesn’t completely disappear. The memory is not erased.”

In this experiment, state-of-the-art neutron detectors identified this elusive state, indicating that a better theoretical framework is needed to understand why sometimes one neutron is emitted and sometimes two are.

“People were searching for it for 20 years and we found it,” Grzywacz said. “Those two neutrons allowed us to see this state.”

He explained that this newly-observed state is an intermediate step in the two-neutron emission process. It’s also the last elementary excitation in the tin-133 nucleus, completing the picture and helping make calculations more accurate.

Better calculations and modeling are tied to the third discovery this research brought to light—the observation of non-statistical population of this newly-observed state. Grzywacz explained that the decay process is relatively clean, so everything is separate with no neighboring states.

“You’re not making split-pea soup,” he said. “Still, in most cases it behaves like split-pea soup. Somehow this statistical mechanism happens. Why is it statistical, even though it shouldn’t be and why in our cast it isn’t”?

The results indicate that as you travel the across the nuclear landscape, farther from stability and into realm of exotic nuclei like Tennessine, the old models don’t hold and new ones are needed.

Tying Multiscale Physics to Bedrock Theory

February 27, 2025

Research Takes UT Faculty and Students to the Extreme

December 12, 2024

Professor Christine Nattrass is among the College of Arts and Sciences faculty working in extreme environments. She talks about her nuclear physics research and the importance of moving the boundaries of what’s possible in this CAS feature.