For The First Time Ever, Physicists See Molecules Form Through Quantum Tunneling

Science requires work. Building molecules typically requires a certain amount of energy, whether it be through rising the temperature, increasing the likelihood that compatible atoms will meet in a heated smash-up, or increasing the pressure and pressing them together.

If you're patient, quantum theory does offer a solution. And in a first-of-its-kind experiment monitoring the merger of deuterium ions with hydrogen molecules, a team of scientists from the University of Innsbruck in Austria has ultimately witnessed quantum tunneling in action.

Due to a peculiarity of the quantum world known as tunneling, electrons appear to be able to traverse barriers that would normally be impossible for them to do so.

The energy needed for atoms to connect with one another or with other compounds is the barrier in chemistry.

However, according to theory, it is theoretically possible for atoms that are near to one another to effortlessly "tunnel" their way through this energy barrier and join.

According to first author Robert Wild, an experimental physicist from the University of Innsbruck, quantum physics enables electrons to cross the energetic barrier because of their wave characteristics.

Quantum waves are the invisible forces that govern the behavior of particles like electrons, photons, and even entire atomic groups. They obfuscate the presence of these particles before any detection, causing them to inhabit a spectrum of potential locations rather than a single fixed location.

For bigger things like molecules, animals, and planets, the blurring is negligible. However, as we focus in on specific subatomic particles, the realm of options widens and compels different quantum waves' location states to intersect.

If that occurs, particles have a small chance of tunneling into areas that would otherwise require a lot of energy to enter, showing where they shouldn't.

The bonding zone of a chemical reaction, which bonds nearby atoms and molecules without the boom-crash-crush of heat or pressure, may be one of those areas for an electron.

Calculating the amount of energy released in nuclear processes, such as those involving hydrogen in stars and fusion reactors on Earth, could be significantly affected by understanding the role quantum tunneling plays in the construction and reordering of molecules.

Although this phenomenon has been modeled for instances involving reactions between dihydrogen, or H2, and a negatively charged form of deuterium, an isotope of hydrogen carrying a neutron, demonstrating the quantities empirically requires a demanding degree of accuracy.

In order to achieve this, Wild and his coworkers cooled negative deuterium ions to a temperature that nearly brought them to a stop before adding a gas composed of hydrogen molecules.

The deuterium ion was much less likely to possess the energy necessary to drive hydrogen molecules into an atomic reordering in the absence of heat. However, it also made the electrons remain still close to one another, giving them more time to form tunneling bonds.

"In our experiment, we allow potential reactions to occur in the trap for approximately 15 minutes before calculating the quantity of hydrogen ions generated. We can determine how frequently a reaction has happened by counting them "Wild elucidates.

According to this calculation, each cubic centimeter experiences just over 5 x 10-20 interactions per second, or one tunneling event for every 100 billion encounters. So not much. Even so, the exercise confirms a benchmark that can be used to make other forecasts and supports earlier modeling.

Given that tunneling plays a significant part in a variety of nuclear and chemical reactions, many of which are likely to take place in the frigid depths of space, having a firm understanding of the relevant variables gives us a better foundation upon which to build our predictions.

This research was published in Nature.