Nav: Home

Lead dressed like gold

February 28, 2017

Since the Middle Ages, alchemists have sought to transmute elements, the most famous example being the long quest to turn lead into gold. Transmutation has been realized in modern times, but on a minute scale using a massive particle accelerator.

Now, theorists at Princeton University have proposed a different approach to this ancient ambition -- just make one material behave like another. A computational theory published Feb. 24 in the journal Physical Review Letters demonstrates that any two systems can be made to look alike, even if just for the smallest fraction of a second.

In this context, for two objects to "look" like each other, they need to reflect light in the same way. The Princeton researchers' method involves using light to make non-permanent changes to a substance's molecules so that they mimic the reflective properties of another substance's molecules. This ability could have implications for optical computing, a type of computing in which electrons are replaced by photons that could greatly enhance processing power but has proven extremely difficult to engineer. It also could be applied to molecular detection and experiments in which expensive samples could be replaced by cheaper alternatives.

"It was a big shock for us that such a general statement as 'any two objects can be made to look alike' could be made," said co-author Denys Bondar, an associate research scholar in the laboratory of co-author Herschel Rabitz, Princeton's Charles Phelps Smyth '16 *17 Professor of Chemistry.

The Princeton researchers posited that they could control the light that bounces off a molecule or any substance by controlling the light shone on it, which would allow them to alter how it looks. This type of manipulation requires a powerful light source such as an ultrafast laser and would last for only a femtosecond, or one quadrillionth of a second. Unlike normal light sources, this ultrafast laser pulse is strong enough to interact with molecules and distort their electron cloud while not actually changing their identity.

"The light emitted by a molecule depends on the shape of its electron cloud, which can be sculptured by modern lasers," Bondar said. Using advanced computational theory, the research team developed a method called "spectral dynamic mimicry" that allowed them to calculate the laser pulse shape, which includes timing and wavelength, to produce any desired spectral output. In other words, making any two systems look alike.

Conversely, this spectral control could also be used to make two systems look as different from one another as possible. This differentiation, the researchers suggested, could prove valuable for applications of molecular detections such as identifying toxic versus safe chemicals.

Shaul Mukamel, a chemistry professor at the University of California-Irvine, said that the Princeton research is a step forward in an important and active research field called coherent control, in which light can be manipulated to control behavior at the molecular level. Mukamel, who has collaborated with the Rabitz lab but was not involved in the current work, said that the Rabitz group has had a prominent role in this field for decades, advancing technology such as quantum computing and using light to drive artificial chemical reactivity.

"It's a very general and nice application of coherent control," Mukamel said. "It demonstrates that you can, by shaping the optical paths, bring the molecules to do things that you want beforehand -- it could potentially be very significant."
-end-
The paper, "Making distinct dynamical systems appear spectrally identical," was published Feb. 24 by Physical Review Letters. The work was supported by grants from the National Science Foundation (CHE 1464569) the U.S. Department of Energy (DE-FG02-02-ER-15344), the Army Research Office (W911NF-16-1-0014), the Defense Advanced Research Projects Agency (DARPA) (W911NF-16-1-0062) and AFOSR Young Investigator Research Program (FA9550-16-1-0254).

Princeton University

Related Molecules Articles:

The inner lives of molecules
Researchers from Canada, the UK and Germany have developed a new experimental technique to take 3-D images of molecules in action.
Novel technique helps ID elusive molecules
Stuart Lindsay, a researcher at Arizona State University's Biodesign Institute, has devised a clever means of identifying carbohydrate molecules quickly and accurately.
How solvent molecules cooperate in reactions
Molecules from the solvent environment that at first glance seem to be uninvolved can be essential for chemical reactions.
A new way to display the 3-D structure of molecules
Berkeley Lab and UC Berkeley Researchers have developed nanoscale display cases that enables new atomic-scale views of hard-to-study chemical and biological samples.
Bending hot molecules
Hot molecules are found in extreme environments such as the edges of fusion reactors.
At attention, molecules!
University of Iowa chemists have learned about a molecular assembly that may help create quicker, more responsive touch screens, among other applications.
Folding molecules into screw-shaped structures
An international research team describes the methods of winding up molecules into screw-shaped structures.
Artificial molecules
A new method allows scientists at ETH Zurich and IBM to fabricate artificial molecules out of different types of microspheres.
Molecules that may keep you young and alive
A new study may have uncovered the fountain of youth: plant extracts containing the six best groups of anti-aging molecules ever seen.
Fun with Lego (molecules)
A great childhood pleasure is playing with LegosĀ® and marveling at the variety of structures you can create from a small number of basic elements.

Related Molecules Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Don't Fear Math
Why do many of us hate, even fear math? Why are we convinced we're bad at it? This hour, TED speakers explore the myths we tell ourselves and how changing our approach can unlock the beauty of math. Guests include budgeting specialist Phylecia Jones, mathematician and educator Dan Finkel, math teacher Eddie Woo, educator Masha Gershman, and radio personality and eternal math nerd Adam Spencer.
Now Playing: Science for the People

#517 Life in Plastic, Not Fantastic
Our modern lives run on plastic. It's in the computers and phones we use. It's in our clothing, it wraps our food. It surrounds us every day, and when we throw it out, it's devastating for the environment. This week we air a live show we recorded at the 2019 Advancement of Science meeting in Washington, D.C., where Bethany Brookshire sat down with three plastics researchers - Christina Simkanin, Chelsea Rochman, and Jennifer Provencher - and a live audience to discuss plastics in our oceans. Where they are, where they are going, and what they carry with them. Related links:...