I had heard of ionic and covalent chemical bonds, but not quantum chemistry. Another form of chemical bond was predicted by Enrico Fermi, and now it seems that its existence has been realized.
According to Chris H Green, from the University of Colorado, in the science magazine, Nature:
The creation of diatomic molecules bound by roaming electrons that allow a huge internuclear distance is some achievement. It opens the door to further experimental exploitation of the principles involved.
Victoria Gill, for the BBC, takes up the story:
A molecule that until now existed only in theory has finally been made. Known as a Rydberg molecule, it is formed through an elusive and extremely weak chemical bond between two atoms. The new type of bonding, reported in Nature, occurs because one of the two atoms in the molecule has an electron very far from its nucleus or centre. It reinforces fundamental quantum theories, developed by Nobel prize-winning physicist Enrico Fermi, about how electrons behave and interact.
The Rydberg molecules in question were formed from two atoms of rubidium – one a Rydberg atom, and one a “normal” atom. The movement and position of electrons within an atom can be described as orbiting around a central nucleus – with each shell of orbiting electrons further from the centre. A Rydberg atom is special because it has one electron alone in an outermost orbit – very far, in atomic terms, from its nucleus.
Back in 1934 Enrico Fermi predicted that if another atom were to “find” that lone, wandering electron, it might interact with it. “But Fermi never imagined that molecules could be formed,” explained Chris Greene, the theoretical physicist from the University of Colorado who first predicted that Rydberg molecules could exist. “We recognised, in our work in the 1970s and 80s, the potential for a sort of forcefield between a Rydberg atom and a groundstate [or normal] atom. “It’s only now that you can get systems so cold, that you can actually make them.”
Very cold here means close to absolute zero, minus 273 degrees Celsius.
Importantly this story has an Einstein connection:
Professor Greene’s prediction that Rydberg molecules could exist was inspired by another Nobel prize-winning piece of physics research.
When, in 1924 the Indian physicist Satyendra Nath Bose sent some theoretical calculations about particles to Albert Einstein, Einstein made a prediction. He said that if a gas was cooled to a very low temperature, the atoms would all suddenly collapse into their “lowest possible energy state”, so they would be almost frozen and behave in an identical and predictable way.
At the time, the Bose-Einstein condensation was a new way of thinking about matter (and energy?). This research, unlike genetic engineering for example, will remain a ethics free zone, until somebody finds a way perhaps in conjunction with funding to use it in the manufacture of weapons. But then again who can say what the implications might be, other than the quest to understand how nature works?
In this case, there is no a set of people arguing contrarily that it just is not so, although the material conditions of scientific research and its significance are not irrelevant factors. Nobody is accusing the publication, Nature, of being sub standard. I suppose that science as a human activity cannot but be political and social.
Qualification:
This post is to diversify the context, not a claim of any insight into the subject.