There’s something about pictures. The first real, graphical images of the DNA double helix were greeted with something approaching a sigh of relief — by that time there was of course absolutely no doubt whatsoever that DNA was arranged in the double-helical structure we all know so well, but actually seeing it still had a visceral effect. We had taken readings that could just as accurately be called “images,” but they were abstract things like the ring-patterns produced by x-ray crystallography. They didn’t really look like anything to anybody but experts in obscure fields of microscopy. There’s something about actually seeing a structure that can affect not just the lay-people in the public sphere, but hard scientists, too.

A few months ago, we covered the first glimpses of some images at an even smaller scale, finally displaying structures of a sort we’ve known about for decades but had yet to actually visualize. The scientists involved call it an “amazing” event — imagine their excitement, actually being able to see the molecule they’ve been studying for so long in the abstract. It’s not just about seeing this particular molecule, however; in picturing the atomic structure of this multi-ringed hydrocarbon they also beautifully confirmed the utility of the classical diagrams that have been in use since long before most modern scientists were born.

The molecule under investigation has the easy-to-remember name of phenylene-1,2-ethynylene, and the researchers wanted to know how it reacted under certain conditions. Their ultimate goal was to find a way to induce the formation of large sheets of stable, aromatic hydrocarbon rings of the sort that characterize graphene, but they were having trouble figuring out whether their reaction was actually giving rise to the product they wanted. Ultimately, they decided that an ultra-high resolution imaging solution was the best way to identify their reaction’s products.

After some false starts, the team settled on a technique called non-contact atomic force spectroscopy. This uses an extremely tiny probe to pick up changes in mechanical force as it moved over the surface of an atom. The metaphor of the needle of a record player is appropriate, except that in this case the “needle” is a single oxygen atom added through adsoption of a molecule of carbon monoxide.

With the molecule immobilized in a flat silver surface, Fischer explains that they can move their atomic “finger” over the sample surface to moving a human finger over Braille, using vibrations in the atomic version as a measure of the strength of certain atomic forces. Mapping those readings in 2D produces a picture, and the pictures they produced were stunning.

“We weren’t thinking about making beautiful images; the reactions themselves were the goal,” said Felix Fischer, a researcher with the Berkeley team that produced the pictures. Still, the beautiful images have gotten them quite a bit of attention even now, before they’ve published the actual experimental data the images represent. In this case, the data itself has arrested the imagination of scientists around the world. They had immobilized their molecule on silver and used an incredibly high-resolution probe, producing images that are sure to be staples of every organic chemistry textbook for decades.

The most striking thing about the images is the extreme resemblance they have to the line diagrams familiar to anyone who’s taken an introductory chemistry course. In such a diagram, the lines represent linking forces called chemical bonds, and the vertices represent the carbon atoms that make up the molecule’s backbone; in these new images, the lines are areas of actual force, the vertices actual carbon atoms.

The chalk lines scratched out on many a blackboard representing chemical bonds say that there will be some sharing of electrons between the two atoms the line connects, and that this sharing holds the atoms together in the molecule; in these new images, the lines are simply where the probe detected the most electron density. As a result, the similarity to the traditional diagrams even seems to extend to largely arbitrary symbology; by convention we represent a double bond (the sharing of two electrons) with two lines, and that doubled intensity results in a thicker band connecting two atoms.

Many frustrated chemistry students have wondered aloud why they are being forced to memorize a method of diagramming that is still, ultimately, a metaphor. Those objections will be a lot harder to raise with these pictures in a teacher’s arsenal.

The content of the images was also interesting, of course. In trying to see if a chain of their molecule would decay into a graphene-like configuration, they discovered that there were two distinct products being made, each with different implications for creating graphene from scratch. The researchers believe the second of their two products may in fact be an artifact of the silver surface that makes the images possible — for get both chemistry and microscopy right at once will require some big steps forward from here.

Now read: Graphene supercapacitors created with ‘traditional paper making’ process, rivals lead-acid battery capacity

Research paper: doi: 10.1126/science.1238187 — “Direct Imaging of Covalent Bond Structure in Single-Molecule Chemical Reactions”