First experimental evidence of quantum monodromy

Jun 21, 2005

Ohio State University physicists have obtained the first-ever experimental evidence of a particular quantum mechanical effect –- one that was theorized a decade ago.
The effect, called quantum monodromy* (Greek for "once around"), relates in part to the behavior of molecules based on their atomic structure and vibrational frequencies. A better understanding of quantum monodromy could have implications in astronomy, atmospheric science, and biology.

The physicists reported their results at the 60th International Symposium on Molecular Spectroscopy, held at Ohio State University .

In some molecules, the atomic bonds act like joints where the molecule can bend and rotate unusually far from their normal positions, like a human arm can bend or rotate at the elbow or shoulder, explained Manfred Winnewisser, adjunct professor of physics at Ohio State . The movement changes the shape of the molecule, and affects its vibrational and rotational energy as well as how it interacts with other molecules.

The water molecule, for instance, exhibits this behavior, and scientists suspect that the bending of that molecule might affect the function of water vapor in the atmosphere.

“In order to understand the absorption of solar radiation in the atmosphere, one has to understand the proper physics,” Winnewisser said. “So an improved understanding of physics or chemistry or biology is actually the most important application of studies of monodromy.”

To understand the movement of such molecules, scientists draw a graph, a kind of map of the molecule's energy. For molecules that exhibit quantum monodromy, the map looks like an upright cylinder with a bulge rising from the bottom, like the bottom of a wine or champagne bottle.

The top of the bulge is a critical point where the shape of the molecule changes, Winnewisser said.

To learn more about what happens at this “monodromy point,” the Ohio State physicists studied the molecule cyanogen isothiocyanate (NCNCS). Its atoms fit together in a long chain that they hoped would exhibit the bending they wanted to see.

A special laboratory instrument enabled the test. Frank De Lucia, professor of physics at Ohio State, and his colleagues designed the instrument to utilize their FAst Scan Submillimeter Spectroscopy Technique (FASSST).

The technique offers a quick way for scientists to examine the spectrum of electromagnetic radiation absorbed by a molecule. Each molecule has its own one-of-a-kind spectral pattern, like lines in a bar code. FASSST takes a quick scan of a wide range of spectral wavelengths, so scientists can easily recognize the pattern of the molecule they are looking for.

In the case of the NCNCS molecule, Winnewisser and his colleagues used FASSST to record a series of spectral features, including the features corresponding to the energy of the molecule at the monodromy point.

Ivan Medvedev, a doctoral student in physics, and his colleagues, then used software he developed to reveal patterns in the spectrum. The open-source software, called Computer Aided Assignment of Asymmetric Rotor Spectra (CAAARS), is available for download from Medvedev's Web page ( www.physics.ohio-state.edu/~medvedev/caaars.htm ).

When they plotted the spectrum with CAAARS, the physicists could identify patterns that exactly matched patterns in the predicted spectrum for a molecule exhibiting quantum monodromy.

Other team members on this project included Brenda Winnewisser, also adjunct professor, and Markus Behnke, a postdoctoral researcher, both of the Ohio State Department of Physics, and Stephen Ross, professor of physics at the University of New Brunswick in Canada.

*Note: More about quantum monodromy

Source: Ohio State University

Explore further: An efficient approach to concentrate arbitrary N-particle W state

Related Stories

Porous, layered material can serve as a graphene analog

May 19, 2015

An electrically conductive material, with layers resembling graphene (single sheet of graphite), was synthesized under mild conditions using a well-known molecule that allows good electronic coupling of nickel ...

Towards the ultimate model of water

May 08, 2015

Researchers from the National Physical Laboratory (NPL), IBM and the University of Edinburgh have developed the first conceptually simple but broadly applicable model for water.

Many uses in researching quantum dots

May 04, 2015

It's easier to dissolve a sugar cube in a glass of water by crushing the cube first, because the numerous tiny particles cover more surface area in the water than the cube itself. In a way, the same principle applies to the ...

Recommended for you

How researchers listen for gravitational waves

4 hours ago

A century ago, Albert Einstein postulated the existence of gravitational waves in his General Theory of Relativity. But until now, these distortions of space-time have remained stubbornly hidden from direct ...

What's fair?: New theory on income inequality

15 hours ago

The increasing inequality in income and wealth in recent years, together with excessive pay packages of CEOs in the U.S. and abroad, is of growing concern, especially to policy makers. Income inequality was ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.