Research, teaching and outreach in Physics at UW–Madison
Year: 2022
Thad Walker honored with Vilas Distinguished Achievement Professorship
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Thad Walker
Extraordinary members of the University of Wisconsin–Madison faculty, including physics professor Thad Walker, have been honored during the last year with awards supported by the estate of professor, U.S. senator and UW Regent William F. Vilas (1840-1908).
Walker was one of seventeen professors were named to Vilas Distinguished Achievement Professorships, an award recognizing distinguished scholarship as well as standout efforts in teaching and service. The professorship provides five years of flexible funding — two-thirds of which is provided by the Office of the Provost through the generosity of the Vilas trustees and one-third provided by the school or college whose dean nominated the winner.
In addition, nine professors received Vilas Faculty Mid-Career Investigator Awards and six professors received Vilas Faculty Early Career Investigator Awards.
Detailed analysis of old star provides template for heavy element formation
The fusion furnaces that are the universe’s stars create the elements from helium up to iron. But iron is only number 26 on the periodic table out of well over 100 known elements. So the heavier ones, like gold, lead and uranium, must come from somewhere other than fusion.
Scientists have long known that those heavy elements come from neutron capture, where neutrons are added to an element that make it unstable, then it radioactively decays and its atomic number increases by one. Nearly 70 years ago, they confirmed one site, or event, of a neutron capture method known as the slow, or s-process. The rapid, or r-process, was not confirmed with a site until 2017, when the LIGO/VIRGO collaboration detected a neutron star merger.
“With a neutron star merger, the neutron stars are ripped apart and they throw out neutrons, and you can build lots of heavy elements out of these neutron stars,” says Jim Lawler, a professor of physics at the University of Wisconsin–Madison. “The mystery arises when we look at the total r-process inventory of our home galaxy: Can we explain all that with neutron star mergers or are there additional sites?”
In a new study led by astronomers from the University of Michigan, Lawler and colleagues identified the elemental composition of HD 222925, a Milky Way star located over 1400 lightyears from earth. Their analysis confirmed that the star was rich in r-process elements, and they were able to identify and calculate the relative abundance of each element. They also found that the star is iron- and metal-poor, a proxy for age that indicates HD 222925 is relatively old and provides information about early star formation.
“We were able to determine a complete r-process abundance pattern for what we think is probably one event that happened early in the beginning of the universe,” Lawler says. “So that r-process template now can be used to screen various models of the nuclear physics that produce the r-process and see if the models for all sites are physically correct.”
At UW–Madison, Lawler and scientist Elizabeth Denhartog contributed the spectroscopic analysis that identified the elements in the star. Every element has a unique electromagnetic spectrum that can be separated into spectral lines using a diffraction grating — just like a prism separates white light into a rainbow. HD 222925 is a relatively bright star, meaning it provided stronger spectra to analyze. It was also identified by the Hubble Space Telescope, providing access to data in the ultraviolet range that is normally blocked by the ozone layer and undetectable by telescopes on Earth.
THIS STUDY WAS SUPPORTED IN PART BY NASA (GRANTS GO-15657, GO-15951, AND 80NSSC21K0627); U.S. NATIONAL SCIENCE FOUNDATION (NSF, GRANTS PHY 14-30152, OISE 1927130, AST 1716251 AND AST 1815403); AND THE U.S. DEPARTMENT OF ENERGY (GRANT DE-FG02-95-ER40934); AND NOIRLAB, WHICH IS MANAGED UNDER A COOPERATIVE AGREEMENT WITH THE NSF.
Researchers aim X-rays at century-old plant secretions for insight into Aboriginal Australian cultural heritage
For tens of thousands of years, Aboriginal Australians have created some of the world’s most striking artworks. Today their work continues long lines of ancestral traditions, stories of the past and connections to current cultural landscapes, which is why researchers are keen on better understanding and preserving the cultural heritage within.
Secretions called exudate cover parts of the spike of a Xanthorrhoea plant — colloquially called “grass tree” or “yakka” — used in aboriginal art. PHOTO COURTESY FLINDERS UNIVERSITY, SOUTH AUSTRALIA
In particular, knowing the chemical composition of pigments and binders that Aboriginal Australian artists employ could allow archaeological scientists and art conservators to identify these materials in important cultural heritage objects. Now, researchers are turning to X-ray science to help reveal the composition of the materials used in Aboriginal Australian cultural heritage – starting with the analysis of century-old samples of plant secretions, or exudates.
Aboriginal Australians continue to use plant exudates, such as resins and gums, to create rock and bark paintings and for practical applications, such as hafting stone points to handles. But just what these plant materials are made of is not well known.
Therefore, scientists from six universities and laboratories around the world turned to high-energy X-rays at the Stanford Synchrotron Radiation Lightsource (SSRL) at the Department of Energy’s SLAC National Accelerator Laboratory and the synchrotron SOLEIL in France. The team aimed X-rays at ten well-preserved plant exudate samples from the native Australian genera Eucalyptus, Callitris, Xanthorrhoea and Acacia. The samples had been collected more than a century ago and held in various institutions in South Australia.
The results of their study were clearer and more profound than expected.
“We got the breakthrough data we had hoped for,” says Uwe Bergmann, physicist at the University of Wisconsin–Madison and former SLAC scientist who develops new X-ray methods. “For the first time, we were able to see the molecular structure of a well-preserved collection of native Australian plant samples, which might allow us to discover their existence in other important cultural heritage objects.”
Researchers today published their results in the Proceedings of the National Academy of Sciences.
Uwe Bergmann
Looking below the surface
Over time, the surface of plant exudates can change as the materials age. Even if these changes are just nanometers thick, they can still block the view underneath it.
“We had to see into the bulk of the material beneath this top layer or we’d have no new information about the plant exudates,” SSRL Lead Scientist Dimosthenis Sokaras says.
Conventionally, molecules with carbon and oxygen are studied with lower-energy, so-called “soft” X-rays, that would not be able to penetrate through the debris layer. For this study, researchers sent high-energy X-ray photons, called “hard” X-rays, into the sample. The photons squeezed past foggy top layers and into the sample’s elemental arrangements beneath. Hard X-rays don’t get stuck in the surface, whereas soft X-rays do, Sokaras says.
Once inside, the high-energy photons scattered off of the plant exudate’s elements and were captured by a large array of perfectly aligned, silicon crystals at SSRL. The crystals filtered out only the scattered X-rays of one specific wavelength and funneled them into a small detector, kind of like how a kitchen sink funnels water drops down its drain.
Next, the team matched the wavelength difference between the incident and scattered photons to the energy levels of a plant exudate’s carbon and oxygen, providing the detailed molecular information about the unique Australian samples.
Century-old plant exudate samples in amber jars. Researchers mapped the chemistries of these samples using high-energy photons, knowledge that will help study and preserve the work of aboriginal artists who used plant material. PHOTO COURTESY FLINDERS UNIVERSITY, SOUTH AUSTRALIA
A path for the future
Understanding the chemistries of each plant exudate will allow for a better understanding of identification and conservation approaches of Aboriginal Australian art and tools, Rafaella Georgiou, a physicist at Synchrotron SOLEIL, said.
“Now we can go ahead and study other organic materials of cultural importance using this powerful X-ray technique,” she says.
Researchers hope that people who work in cultural heritage analysis will see this powerful synchrotron radiation technique as a valuable method for determining the chemistries of their samples.
“We want to reach out to that scientific community and say, ‘Look, if you want to learn something about your cultural heritage samples, you can come to synchrotrons like SSRL,’” Bergmann says.
SSRL is a DOE Office of Science user facility. In addition to SSRL, parts of this research were carried out at SOLEIL in France and three CNRS laboratories (PPSM, IPANEMA, IMPMC). The University of Pisa, the Université Paris-Saclay, the University of Melbourne, Flinders University, the Australian Synchrotron International Synchrotron Access Program, and other organizations also supported this research.
Kevin Anderson ’83 never abandoned his youthful passion, and now he’s one of the most successful authors in his field.
When he was growing up in Wisconsin, there was little on the surface of Kevin Anderson ’83’s life to suggest he’d become one of the world’s most prolific science-fiction authors.
“I was an alien child, I think,” says Anderson, who grew up first in Racine and then in Oregon, outside of Madison. “My dad was a bank president, and my mom was an accountant. We didn’t have an artsy streak in our family.”
Still, when Anderson was five, he saw the 1953 film The War of the Worlds and was mesmerized. Later he raced through the Ray Bradbury paperbacks he checked out of his school library, and he was left with one consuming thought.
“I wanted to tell stories like that,” he says.
In ninth grade, Anderson submitted his first science fiction story to a magazine.
“I got my first rejection slip,” he says. “I now have around 800 rejection slips. But I’ve had a couple of successes, too.”
You could say that. Anderson, who turns 60 in 2022 and now lives with his wife, Rebecca Moesta, outside Colorado Springs, has published a staggering 175 books, though that number may already be dated. Many have landed on various best-seller lists.
He has written Star Wars novels, X-Files novels, Dune novels in collaboration with Brian Herbert (son of Dune creator Frank Herbert), and even steampunk fantasy novels with a rock-and-roll star for a coauthor. Clockwork Lives, Anderson’s second novel with the late Rush drummer, Neil Peart, is his favorite among all his books.
The genesis of their unlikely friendship is itself a good tale. It followed the appearance of Resurrection, Inc., Anderson’s first novel, published when he was 25 and working as a technical writer at the Lawrence Livermore National Laboratory in California.
Anderson got the Livermore job after graduating from UW–Madison with a degree in physics and astronomy and a minor in Russian history. He took a few writing classes but says, “I guess I wanted to know things to write about rather than how to write. I wanted to have ingredients, not cookbooks.”
Recalling his time at the UW, Anderson notes, “I loved the campus and student life. I still miss Rocky Rococo’s pizza. That was one of my main food groups.”
More seriously, he adds, “Growing up in a small town was great. But being sort of an odd duck who liked to read comic books and make up stories about space battles and things — I didn’t have a whole lot of people that I had much in common with. It wasn’t until I got to the university that I found other writers and creative people.”
Resurrection, Inc. was inspired by the Rush album Grace under Pressure. Anderson had admired the band for years. He sent signed copies of the novel to Mercury Records, asking that they be forwarded to Rush, not really expecting that to happen.
Yet Peart not only received the novel, he loved it and sent Anderson a seven-page, single-spaced letter saying so. A correspondence ensued. The friendship included yearly invitations for Anderson to hang backstage at Rush concerts. It was in 2010 while hiking on a mountain in Colorado — a passion of Anderson’s — that the two agreed to collaborate on a novelization of Rush’s album Clockwork Angels. The book appeared in 2012.
Anderson has published a staggering 175 books, with many landing on various best-seller lists.
When Anderson met Moesta, a science-fiction fan who was working as a proofreader and copy editor at the Livermore lab, “we hit it off right away,” he says. In three decades of marriage, they’ve coauthored dozens of books, including an entire series of Star Wars adventures for young adults. They moved to Colorado in 1997, and in 2021, Anderson was inducted into the Colorado Authors’ Hall of Fame.
Anderson’s writing has paid off handsomely. A 1997 Publishers Weekly article stated that he and Herbert had signed a $3 million deal for a trilogy of sequels to Dune. Anderson’s website notes that 23 million copies of his books are in print in more than 30 languages.
These days he’s busier than ever. Anderson teaches writing at Western Colorado University, and he and Moesta have a publishing company, WordFire Press, that has released some 400 titles.
When his schedule allows, Anderson likes to write in the mornings. But he doesn’t sit at a computer. Instead, he heads outside and talks.
“I do all my writing on a digital recorder,” he says. “I love to go out on the trail and dictate — usually two chapters a morning. I go for a walk and tell myself a story. I send it off to a transcriptionist, who sends it back. Then I have to polish it, of course.”
Anderson has several titles coming in 2022, including the third book in the Dune trilogy and the last novel in his Clockwork series with Peart, who died in 2020. More will surely follow. This is an author who loves what he’s doing.
“It’s exactly what I’ve wanted to do since I was five years old and saw War of the Worlds,” he says. “Not many people can say they’ve built their entire career on what they wanted to be when they were a little kid.” •
Thirty-two members of the University of Wisconsin–Madison faculty — including physics professor Mark Saffman — have been awarded fellowships from the Office of the Vice Chancellor for Research and Graduate Education for 2022-23. The awardees span the four divisions on campus: arts and humanities, physical sciences, social sciences and biological sciences.
“These awards provide an opportunity for campus to recognize our outstanding faculty,” says Steve Ackerman, vice chancellor for research and graduate education. “They highlight faculty efforts to support the research, teaching, outreach and public service missions of the university.”
The awards are possible due to the research efforts of UW–Madison faculty and staff. Technology that arises from these efforts is licensed by the Wisconsin Alumni Research Foundation and the income from successful licenses is returned to the OVCRGE, where it’s used to fund research activities and awards throughout the divisions on campus.
Mark Saffman was awarded a WARF professorship. These professorships come with $100,000 and honor faculty who have made major contributions to the advancement of knowledge, primarily through their research endeavors, but also as a result of their teaching and service activities. Award recipients choose the names associated with their professorships. Saffman, the Johannes Rydberg Professor of Physics and director of The Wisconsin Quantum Institute, first began work on atomic physics and initiated a long-term effort to develop quantum computers. He is known for his research as a leader in the ongoing development of atomic quantum computers based on the Rydberg blockade mechanism.
In addition, physics affiliate professor Mikhail Kats received a Romnes Faculty Fellowship.
Congratulations to Professor Lawler on his retirement!
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After 42 years on the UW–Madison faculty, Jim Lawler, the Arthur and Aurelia Schawlow Professor of Physics, has announced his retirement. Lawler is an atomic, molecular & optical physicist with a focus developing and applying laser spectroscopic techniques for determining accurate absolute atomic transition probabilities. His retirement is official as of May 22.
“What we’ve really done gradually over four-plus decades is make atomic spectroscopy more quantitative so that people can use it to really learn the detailed physics and chemistry of the remote universe,” Lawler says.
Lawler received his MS (’74) and PhD (’78) from this department, studying with now-professor emeritus Wilmer Anderson. In the two years after earning his doctorate, he was a research associate at Stanford University, and returned to UW–Madison as an assistant professor in 1980.
“There was a little bit of a disadvantage to come back to a place where I had recently been as a student,” Lawler says. “But I knew I would get extremely good graduate students and I would have access to a lot of infrastructure, and that combination really drew me back.”
He had extremely good graduate students and postdocs. Lawler supervised 26 PhD students and 10 terminal MS students. Those students and postdocs have gone on to prestigious National Research Council Fellowships, group lead positions at major companies, and tenured professorships, amongst many others.
Lawler served as department chair from 1994-1997. He also accumulated numerous awards and honors over his distinguished career. He is a fellow of the American Physical Society, the Optical Society of America, the U.K. Institute of Physics, and in 2020 he was elected a Legacy Fellow of the inaugural class of American Astronomical Society Fellows. He won the 1992 W. P. Allis Prize of the American Physical Society and the 1995 Penning Award from the International Union of Pure and Applied Physics for research in plasma physics, the two highest National and International Awards in the field of Low Temperature Plasma Physics. In 2017, he won Laboratory Astrophysics Prize of the American Astronomical Society for research in spectroscopy.
Longtime collaborator Blair Savage, UW–Madison professor emeritus of astronomy, says:
“Jim’s work in laboratory astrophysics provided extremely important atomic ultraviolet transition probabilities in support of the Hubble Space Telescope programs to determine elemental abundances of gaseous matter in the interstellar medium from three different ultraviolet spectrographs over the 32-year history of the space observatory. They included the Goddard High Resolution Spectrograph, the Space Telescope Imaging Spectrograph and the Cosmic Origins Spectrograph.”
And Wilmer Anderson, Lawler’s doctoral advisor, says:
“He was a very good graduate student, and he of course has turned out to be a really great scientist and colleague. His lifetime measurements on atomic physics played a key role in understanding the neutron star collisions. I’m sorry to see him retiring but I’m sure that he will leave a legacy behind that’s really fantastic. It’s going to be a big loss to the department not to have him around.”
Lawler has collaborated with his AMO colleagues over the years, but in more of an intellectual capacity than in research. As he notes, much of AMO is headed in the quantum information and quantum computing direction, with public and private funding helping to drive it. Still, he does not see AMO headed solely in the quantum direction.
“Decades from now the currently Hot areas of physics will be less glamorous, but those stars are still going to be light years away,” Lawler says. “I think the connection of astronomy and spectroscopy — the way we learn about the physics and chemistry of the remote universe — is strong enough that it will survive. And helping make spectroscopy in astronomy more quantitative is what we’ve done that will have some lasting significance.”
Congrats, grads!
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Congrats to all of the Physics and AMEP students who are graduating this weekend! Their names are listed below. Best of luck to all of you on your future endeavors — we know you’ll do great things!
Congrats, Spring 2022 grads! (* denotes graduating with honors)
Physics undergraduates named 2022 Hilldale Fellows
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Three UW–Madison undergraduate physics majors have been named 2022 Hilldale Fellows, in addition to one engineering physics major who is conducting their research in the Physics Department.
The Hilldale Undergraduate/Faculty Research Fellowship provides research training and support to undergraduates at UW–Madison. Students have the opportunity to undertake their own research project in collaboration with UW–Madison faculty or research/instructional academic staff. Approximately 97 – 100 Hilldale awards are available each year.
The students are:
Astronomy-Physics and Physics major Elyse Incha, in Susanna Widicus Weaver’s group (Chemistry)
Mathematics and Physics major Haoyi Jia, in Sridhara Dasu’s group (Physics)
Music and Physics major Daniel Laws, in Mary Halloran’s group (Integrative Biology)
Engineering physics major Nico Ranabhat, in Shimon Kolkowitz’s group (Physics)
Lee Pondrom’s High Energy Physics textbook now available
Summary: Elementary particle physics is a mature subject, with a wide variety of topics. Size considerations require any text to make choices in the subject matter, and such choices are to a large extent a matter of taste. Each topic in this text has been selected for its accessibility to as wide an audience of interested readers as possible, without any compromise in mathematical sophistication. There are of necessity a lot of formulas, but every one is derived, and an effort has been made to explain the various steps and clever tricks, and how to avoid pitfalls. The text is supplemented by exercises at the end of each chapter. The reader is urged to do the exercises that are designed to increase one’s skills in the material. The goal of the book is to bring to undergraduates an ability to enjoy this interesting subject.
Overall, forty-five textbooks have been awarded 2022 Textbook Awards by TAA. 12 textbooks received William Holmes McGuffey Longevity Awards, 13 textbooks received Textbook Excellence Awards, and 20 textbooks received Most Promising New Textbook Awards.
The awardees were recognized during an awards ceremony today, April 27.
A testimony in support of the award for Physics in the Arts says:
“Physics in the Arts is the third edition of a textbook which makes physics intriguing and even fun. It is a great effort in connecting complex physics principles with procedures and activities of artists. As artists and artisans, we create and share the beautiful through light and sound. For those of us interested in the aesthetic side of life, this book shows how a physical understanding of light and sound can expand and deepen our appreciation of the world opened up by these media. Understanding the concepts and connections of the book make their professional lives more fulfilling and more efficient.”
