New Vibrations!

Posted on Wednesday, March 4th, 2015 by Semanti Mukhopadhyay

Ever wondered how must it feel to discover something exhilaratingly new? Some reports, some findings that threaten to shake the mere foundations of your understanding of science at large? Looking at the downside, how must it feel to be belittled by your contemporaries who refuse to accept your explanations?

Not digressing any further, let us tell you a story! A story of perseverance. And of discovery!

It all started in 1989, when a team of scientists led by Dr. Donald Fleming at the University of British Columbia at Vancouver, were investigating a queer case of anomaly in a nuclear reaction. The idea was to study how Muonium (a complex atom which is basically a hydrogen isotope consisting of an electron orbiting an antimuon nucleus) reacts with various elements. A little background knowledge here, if you please? A basic tenet of thermodynamics dictates that the rates of reaction speed up when the reaction temperature is increased. When the Muonium was reacted with Chlorine and Fluorine, the reactions sped. However, to the shock, surprise and euphoria of the team, when Bromine was made to react with Muonium, the reaction time sped up as the temperature decreased!

Now, we all appreciate how important chemical bonds are to us, our lives and our mere existence. Without the formation of bonds, there would most definitely be no existence of life. Why, you ask? Consider the analogy of small cubes. You would like to build a castle out of them, but you can’t because some adhesive, some force that can hold it together, is absent. A gust of air can blow out your castle and thus, by analogy, our lives!

Mindful of the above, how did the unexpected reaction land up having its own unique chemical bond? Well, Fleming hypothesised that when the reacting species made contact, they formed a transitional structure: one lightweight atom flanked by two heavier atoms. What is interesting about this hypothesis is that it says that the structure, instead of being held together by van der Waal’s forces, is joined by some kind of temporary Vibrational Bond. In such a scenario, the lightweight muonium atom would move rapidly between two heavy bromine atoms, or, to quote Fleming, 'like a Ping Pong ball bouncing between two bowling balls”. The oscillating atom would briefly hold the two bromine atoms together and reduce the overall energy, and therefore speed, of the reaction.

It wasn’t the first time that such a bond was mentioned, but, even then why did it not garner enough limelight? Why is it not included in our NCERT textbooks yet? That is simply because they lacked evidence. An in-situ observation of the reaction wasn’t possible then because of the limited technology. However, after prolonged years of waiting, the team has successfully completed their observations at the nuclear accelerator at Rutherford Appleton Laboratory at England.

It sure looks like the vibrational energy ate up the incident energy when the temperature was increased, and hence, there wasn’t enough energy to witness any increase in reaction rate!

However fantastic the discovery may seem, it is yet to be observed in any other system. While more systems are expected to behave in a similar fashion, it sure looks like a very specific case. And while the discovery might be very impactful, it may also reduce down to yet another syllable to be committed to rote memory, for to change how chemistry is presently viewed, it will have to compete with some very strong forces (Covalent interactions, for instance)!!

Only time will tell, right?

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