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03/16/2026 | Press release | Distributed by Public on 03/16/2026 09:14

Blink and You’ll Miss It: Haiwang Yong’s Research Happens in a Fraction of a Second

Published Date

March 16, 2026

Article Content

If you think "instantaneous" happens in a second, you should meet Haiwang Yong. An assistant professor of chemistry at the University of California San Diego, Yong uses ultrafast spectroscopy to observe the motion of atoms and electrons in femtoseconds, equal to 10-15 of a second. Last year, Yong received an Early Career Research Program award from the U.S. Department of Energy (DOE), and more recently he was awarded a $1.1 million grant from the W.M. Keck Foundation to support his work. In this Q&A, he talks to us about life in the ultrafast lane.

Tell us about your research.

My research group is interested in observing what happens, at the atomic level, during chemical reactions using ultrafast spectroscopy and diffraction on the femtosecond timescale. What makes us different from other groups is our interest in the spatial information of the molecule - how atoms and electrons move in real space and time.

Can you explain how you make such fast observations?

Haiwang Yong (seated) and members of his research group conducting an experiment at SLAC National Accelerator Laboratory.

We mainly use two techniques: ultrafast X-ray scattering and ultrafast electron diffraction. First, we hit the sample with a laser pulse to excite the molecules - this initiates the chemical reaction. Then we probe the sample with ultrashort X-ray pulses or electron pulses. The photons or electrons in the probe are scattered by the electrons and nuclei within the molecules. These scattered photons or electrons can provide structural information about the molecule.

Tell us about the work you're doing for your DOE Early Career Award.

We are studying ultrafast processes in solution-phase chemistry. While the role of solvents in solution chemistry is well-defined, the initial stages of a reaction, particularly how the dynamics evolve, are not well understood.

In our work, the sample is a solution that involves a solute and solvent. The goal is to observe how the solvent molecules react with the solute after the solute molecule absorbs a photon.

This is fundamental research. We want to understand how solvent molecules actively participate in chemical reactions and how they can affect the energy of the solution. With that kind of information, there could be many applications.

You received a $1.1 million award from the Keck Foundation. Tell us about that.

I'm very excited about this. We're trying to study isolated gas-phase molecules. A photon carries a certain amount of energy. When a molecule absorbs a photon, it absorbs that energy and the molecule is elevated to an excited state. There are two primary ways a molecule can release this energy.

One is known as radiative relaxation. In this case you will see something like fluorescence. Basically, the molecule relaxes back to its ground state and emits a photon. This process happens relatively slowly, over picosecond or nanosecond timescales.

However, there are systems, such as the human eye, that don't emit the absorbed photon. Rather, when the retina absorbs a photon, the energy is converted into a structural change. In this case, the retina undergoes an ultrafast process that converts light energy into molecular motion. This initiates a biochemical cascade that ultimately allows us to perceive light.

That process happens very rapidly, on the order of a few femtoseconds. It involves nonradiative relaxation through conical intersections, which is a point where two electronic states cross at a certain molecular geometry, allowing rapid transition between them. Many believe this transition happens instantaneously.

What does instantaneous mean in your work?

In my field, probably less than 1 femtosecond. It happens so fast, there's no timestamp. There has been no direct experimental evidence measuring this kind of crossing, so it remains theoretical at this point. That's what we are trying to measure in our experiment.

We're proposing a new ultrafast x-ray diffraction technique using twisted x-rays. From our previous theoretical work, we know that if you use this kind of a light, you could generate a signal that is uniquely sensitive to the conical intersection crossing.

I originally proposed this idea, theoretically, during my postdoctoral work, so it's exciting to pursue it experimentally with support from the Keck Foundation.

How do twisted x-rays work?

We will fabricate a special zone plate, which is essentially a nanostructure patterned on a chip with a spiral shape. When the X-ray passes through the zone plate, it moves in a helical pattern rather than along a straight path. This is well established in optics, but it has not yet been applied to ultrafast molecular diffraction.

Where could this research lead?

Related content

Definitions

Orders of Magnitude

Nanosecond = 1 billionth of a second
Picosecond = 1 trillionth of a second
Femtosecond = 1 quadrillionth of second
Attosecond = 1 quintillionth of second

Solution chemistry: a field of chemistry that studies mixtures where solutes - the substances being dissolved or broken down - are mixed into solvents, the substances that do the dissolving.

Conical intersection: a point or region where two or more electronic potential energy surfaces meet, allowing for instantaneous, nonradiative transitions between different electronic states. They act as "funnels" controlling many photochemical reactions.

A diffraction pattern of molecules taken during an experiment at SLAC.

It's a difficult question because we are relatively far from any real-world applications. At this stage, our goal is to build fundamental knowledge. We may be at the beginning of many years of research before practical industrial applications emerge. However, as we gain more understanding of what is happening at the molecular level, we will be better positioned to manipulate these systems atom by atom.

There may also be important health implications. When our bodies absorb photons, there can be radiation damage to DNA, so the more we understand of how that process happens, the better we can prevent or minimize the damage.

You've been at UC San Diego since 2023. How do you like it?

There is no doubt about this place, I truly enjoy being here. I love San Diego. I like living by the ocean and I like the summer weather. It's a very beautiful campus and it's one of the best public universities.

When I joined as an assistant professor, I received a lot of support from my colleagues in the department. During my first two years, there were ongoing lab renovations, so I didn't have my own space. Bob Continetti generously let me use space in his lab so I could actually do research. Shaowei Li also lent me some lab space in Tata Hall to host my ultrafast lasers during the early stages. I have consistently received helpful advice from other faculty members as well. The facilities staff have also been helpful during the renovations, as my lab space requires precise environmental control for my research.

Where's your favorite place on campus?

I like Geisel Library. The sixth floor has that great view. There are also some nearby hiking paths. I often walk there to relax and think through ideas. It is a very peaceful experience.

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