Purdue University scientists have discovered an entirely new type of weak atomic bond


Scientists have come across an entirely new type of molecule, which they are calling the butterfly Rydberg molecule. First identified back in 2002, this strange molecule is believed to be a weak pairing of excitable atoms, held together by a hitherto-unknown type of atomic bond. According to the researchers, these molecules are generated when an electron is pushed far away from the atom’s nucleus, in turn making it electronically unstable and excited.

While they do exist on their own, it wasn’t until 2002 that Rydberg molecules were found capable of attracting and binding with other atoms. The research, conducted by a group of scientists from Purdue University, was the first to predict the existence of a molecular combination that has come to be known as the butterfly Rydberg molecule, thanks to its unique, butterfly-shaped arrangement of orbiting electrons.

The latest study marks the first time that researchers have been able to observe butterfly Rydberg molecules in the laboratory, some 14 years after the original discovery. As part of the current project, the team has also identified a new kind of weak atomic bond. Speaking about the findings, lead scientist Chris Greene said:

This new binding mechanism, in which an electron can grab and trap an atom, is really new from the point of view of chemistry. It’s a whole new way an atom can be bound by another atom.


These molecules, the physicists state, are unlike anything else, as they contain electrons that are located somewhere between 100 to 1,000 times away from the nucleus than in case of regular molecules. To create the molecules, the team started by cooling Rubidium gas to a very low temperature of around 100 nano-Kelvin, which is equivalent to ten-millionth of one degree above the absolute zero. Following this, they used lasers to excite the atoms into Rydberg molecules.

During the experiment, the scientists observed the activities of the molecules, in order to check if they could combine other atoms. As pointed out by the team, any change in the frequency of light absorbed by the Rydberg molecules would in turn be the result of bond formation. Greene, a professor at Purdue University, explained:

This [distant] electron is like a sheepdog. Every time it whizzes past another atom, this Rydberg atom adds a little attraction and nudges it toward one spot until it captures and binds the two atoms together. It’s a really clear demonstration that this class of molecules exist.

Recently published in the Nature Communications journal, the findings could pave the way for molecular-scale electronics. Thanks to the distantly-revolving electrons, Rydberg molecules could lead to the development of a new class of machines and devices that are larger in size, and require less energy to move around. Greene was reported saying:

The main excitement about this work in the atomic and molecular physics community has related to the fact that these huge molecules should exist and be observable, and that their electron density should exhibit amazingly rich, quantum mechanical peaks and valleys.

Source: Purdue University

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