August 30, 2021

Well, This Is Cool: PNNL’s Bruce Kay Is A Supercooled Water Expert

PNNL physicist prepares to move equipment to new Energy Sciences Center and enhance collaboration with colleagues


PNNL Physicist Bruce Kay, standing in front of a molecular beam surface scattering instrument, is regarded as an international expert on the behavior of water.

(Photo by Andrea Starr | Pacific Northwest National Laboratory)

Bruce Kay maneuvers carefully through an equipment-filled laboratory, glancing at tubes, wires, and various instruments while heading to his destination.

The physicist stops in the middle of the lab, at the stainless steel vessel with windows bolted to hold vacuum that has been at the center of his attention for years.

It’s a molecular beam surface scattering instrument. This device and two others in the room have been Kay’s research partners for about three decades, resulting in numerous studies and cementing Kay’s stature as an international authority on water—how fast reactions occur between molecules and surfaces and also how they convert from solid to liquid to gas. The instruments and Kay will be moving soon to the Energy Sciences Center, the collaborative research hub that is expected to open later this year on the Pacific Northwest National Laboratory (PNNL) campus in Richland, Washington.

“This instrument has two molecular beams that cross at right angles and then they hit a target at the end of this long probe,” said Kay, pausing while giving a tour of his existing PNNL campus laboratory. “And that target is at a very, very cold temperature. In this case it’s 18 degrees kelvin—18 degrees above absolute zero. At that temperature, anything except helium, hydrogen, and neon will stick to the surface.”

Kay, dressed in an orchid-themed Hawaiian shirt and baggy shorts, pauses in delivering his description to emphasize that two long-time PNNL colleagues—physicists Scott Smith and Greg Kimmel—were key players in building this one-of-a-kind instrument along with two other instruments.

It wasn’t just me, Kay emphasizes. It was the two guys who, as postdoctoral researchers in the early 1990s, trusted that the affable 6-foot-3-inch Kay was capable of discovering and achieving big things.

The instruments have been at PNNL almost as long as Kay. He arrived in 1991 as a newly minted laboratory fellow. PNNL leaders recruited Kay from Sandia National Laboratories in Albuquerque, New Mexico, where he’d worked as a staff scientist for 10 years. He’d been sought to be among the first PNNL scientists creating the Molecular Sciences Research Center, which evolved into the Environmental Molecular Sciences Laboratory, known as EMSL, a U.S. Department of Energy (DOE) Office of Science user facility located at PNNL. Today, Kay is the project manager and a principal investigator for the DOE Basic Energy Sciences-funded Experimental Condensed Phase and Interfacial Molecular Sciences Research Program at PNNL.

Chicago South Side to Colorado Rockies

That trajectory could not have been foreseen, of course, when he was a sports-loving kid on Chicago’s southwest side.

His parents emigrated separately, as toddlers, from Lithuania. They met and married after World War II, landing in the early 1950s near South Ashland Avenue and West 84th Street in Gresham, what was then one of Chicago’s European melting pot neighborhoods. His father was a psychologist for Chicago’s public school system, and his mother was an accountant. Kay, an only child, attended public schools, living in a house without a television but a lot of books. He excelled at math, a hint at his future interests.

He stuck close to home for undergraduate studies, graduating from the University of Illinois Chicago with a chemistry degree and nearly enough credits for a mathematics degree. Of several chemical physics programs that caught his eye, he chose the University of Colorado Boulder in part because of the school’s recruitment efforts. Also, he had recently developed an interest in skiing.

Physical chemistry is about understanding the basic nature of energy transfer and bond-breaking underlying how chemical reactions occur,” Kay says. “It tends to be both experimental and mathematical, and I'm predominantly an experimentalist.” I tell people the operational definition of a chemical physicist is a person who knows enough chemistry to confuse the physicist, enough physics to confuse the chemist, and enough mathematics to confuse themselves.”

Classes at the Boulder campus would sometimes conclude at noon. “And we’d drive up to the mountains in the afternoon for night skiing,” Kay says. “There was this one place that had a great deal on a season’s pass for students. I think my first year in graduate school I skied 60 days.”

While at Colorado, he’d also pursue his teenage love of the Grateful Dead, eventually attending 26 of the band’s concerts over the next decade or so, most of them at Red Rocks Amphitheater near Boulder.

Made it at Sandia

Upon completing his PhD research in 1981, Kay was prepared to follow his sense of adventure to Germany for a postdoc fellowship. Serendipity intervened. Before heading to Europe, he paid a visit to a friend in Albuquerque. There, he learned that Sandia National Laboratories existed. With his interest piqued, he made a cold call to someone at the lab whose name he recognized, told them he was interested in learning about the place, had an introductory lunch, and impressed the impromptu suitors. The recruitment continued when Kay returned to Boulder. Sandia offered him a job as a staff scientist.

“I was really looking forward to going to Germany,” he says. “But this is 1981. The economy is horrible, inflation is high, and so is unemployment. I didn’t have any worries, really, about getting a job when I returned. But I knew wherever I went I’d be starting as a postdoc. Sandia was offering me a job as a staff scientist right out of school.”

It was a fortuitous move. Like at PNNL, researchers at Sandia have multiple opportunities to collaborate with colleagues with a range of expertise.

Kay embarked on research involving molecular beam surface scattering, a precursor to experiments he performs today. “You would basically prepare molecules, launch them at a surface, and then they'd scatter off the surface or they’d react,” he says. “And you can actually measure with lasers how fast they would be vibrating or rotating. That was a good opportunity.”

Over the next 10 years, he’d turn down academic and other offers to stay at Sandia, because he loved the interdisciplinary environment. Then PNNL came calling.

Offer he couldn’t refuse

PNNL recruiters told him about the vision for the Molecular Sciences Research Center, which would eventually become EMSL, and about the research funding anticipated for chemical physics work. “It looked like an interesting opportunity,” Kay says. “We’d start from the ground up. And Sandia allowed me to bring a significant amount of beam-scattering equipment with me to PNNL. I’m grateful to that lab and the people I worked with. They wanted me to succeed. It enabled us at PNNL to hit the ground running.”

Shortly after arrival at PNNL in 1991, Kay met two youthful postdocs, Scott Smith and Greg Kimmel, the beginning of 30-year PNNL relationships. Over the next three decades, Kay has collaborated with Smith on about 100 papers, and about 40 with Kimmel. The three would explore the kinetics and dynamics of gas-surface interactions and of supercooled liquids and amorphous solids. Perhaps most importantly, they demonstrated that supercooled water can exist at far lower temperatures than previously believed.

“His biggest strength is his ability to think about problems from a fundamental point of view,” says Smith, a physicist who is acting director of PNNL’s Physical Sciences Division. “He has a deep understanding of the fundamentals of chemical physics, kinetics, and thermodynamics. He can look at the data and think about it from a mathematical point of view and predict what should happen. He's very good at translating the math into a model that can be understood by any other physical chemist.”

“Bruce has this ability to recognize things in an experiment that he doesn’t understand,” says Kimmel, a physicist who has an EMSL lab adjacent to Kay’s, “but also recognize that it’s important. And then he just dives in and figures out the set of experiments that you need to do to understand some aspect of the data. Unraveling the puzzle is always the most fun, for both of us.”

A first in the world of supercooled water

In 2020, Kimmel, Kay, and other PNNL colleagues showed for the first time that extremely cold liquid water exists in two distinct structures that co-exist and vary in proportion dependent on temperature. Previously, liquid water at the most extreme possible temperatures had been the subject of competing theories and conjecture. The ground-breaking study earned a place in the journal Science.

Another postdoc, now a laboratory fellow, chemist Zdenek Dohnalek, soon joined Kay, Smith, and Kimmel in 1998.

In his first visit to the Richland campus, Dohnalek was impressed not only with Kay, his potential collaborator, and with the impressive array of instrumentation at the lab, but also that his personality meshed with Kay’s. “I’m from the Czech Republic, he’s from Chicago,” Dohnalek said, “I could tell quickly we had plenty in common.”

Dohnalek also was grateful that Kay was open to helping the new arrival pursue his research into metal oxides, especially catalysis with oxide processes.

“Bruce is fascinated with a complex level of understanding of how molecules move on surfaces,” says Dohnalek, who is now the deputy director of the Institute for Integrated Catalysis. “He has this unique, fundamental understanding of how kinetics can be taken apart to understand things at a molecular level. What is hidden in the graphs and other measurements that other people may not see? Bruce has a very keen eye on being able to take that apart and be able to see what is happening with molecules. Not too many people can do this.”

Kay has known physicist Greg Schenter, a laboratory fellow and Chemical Sciences Division chief scientist, as long as Smith, Kimmel, and Dohnalek. Schenter started at the lab in 1988.

Kay and Schenter often approach science problems from complementary, and sometimes conflicting, angles. “Mine is a more analytic, more rigorous mathematic approach,” says Schenter. “Bruce has a qualitative, physical understanding of fundamental concepts of physics and chemistry. In the world of science, he is a master chef as opposed to a short order cook.”

Schenter recalled when he began working with Kay they were located in the same building. That didn’t last long, because Schenter was among a group that was moved to a different campus building. Collaboration continued, in large part because they manage complementary programs: Kay with the Experimental Condensed Phase and Interfacial Molecular Sciences Research Program; Schenter with the Theoretical Condensed Phase and Interfacial Molecular Sciences Research Program. Now, Schenter is looking forward to a repatriation with Kay and others with the move to the Energy Sciences Center.

“Long time coming,” Kay says. “I’m looking forward to it.”

Preparing for moving day

Back at his lab in EMSL, Kay glanced up at the maze of exhaust pipes, wires, and tiny tubes that all meet at the molecular beam surface scattering instrument. He agreed that moving the instrument and two others to the Energy Sciences Center would not be as simple as loading a file cabinet onto a hand truck and walking across campus.

“Not only are these instruments big, but these are precision machines,” Kay says. “These apertures, that define these beams, are aligned within a few thousandths of an inch. But a lot of this instrument was designed so things don’t move around, a design that contributes to its precision. Taking apart and putting this back together will give early career staff an opportunity to really see how these instruments work from the inside.”

Equally interesting may be the origins of Kay’s last name.

“My father’s Lithuanian family name was Kazlauskas,” Kay says. “He changed it to Kay when he came back from World War II since he got tired of people mispronouncing it and asking him how to spell it. Surprisingly, I am occasionally asked ‘How do you spell Kay?’ My response is usually ‘Kay’ is ‘Yak’ spelled backwards.”


About PNNL

Pacific Northwest National Laboratory draws on its distinguishing strengths in chemistry, Earth sciences, biology and data science to advance scientific knowledge and address challenges in sustainable energy and national security. Founded in 1965, PNNL is operated by Battelle for the Department of Energy’s Office of Science, which is the single largest supporter of basic research in the physical sciences in the United States. DOE’s Office of Science is working to address some of the most pressing challenges of our time. For more information, visit For more information on PNNL, visit PNNL's News Center. Follow us on Twitter, Facebook, LinkedIn and Instagram.

Published: August 30, 2021

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