Hydrogen is an element that we’re all familiar with as it makes up around 75 percent of the Universe’s total mass and over 90 per cent of atoms. You would have thought that with their being so much hydrogen about we would already know all there is to know about it, but this month scientists have discovered something completely new as physicists from the University of Innsbruck, Austria has created a new form of hydrogen – negatively charged hydrogen clusters.
To better understand what negatively charged hydrogen clusters are, it may be easier first to understand what they’re opposite, positively charged hydrogen clusters, are. More commonly known as hydrogen ion clusters, they can contain as many as 100 different atoms and are formed at very low temperatures. These hydrogen ion clusters were first discovered around 40 years ago, but no one has been able to figure out just how to create one.
But this didn’t stop a team of physicists led by Michael Renzler. Their research consisted of first injecting cold liquid helium drops with hydrogen molecules which caused clusters to form. Next, they exposed these drops to an electron beam, causing ionization of some of the hydrogen molecules, and throwing them out as negatively charged hydrogen ions as a result. Even though these clusters only exist for some microseconds, that’s enough for the team to record the size and shape of them.
On closer scrutiny, the team found that the clusters only had odd atom numbers that ranged from n=5 to n=129. Also, the most stable of them had a central, negatively charged H-ion core that was surrounded by shells containing more hydrogen molecules. Michael Schirber of the American Physical Society, said, “The odd values implied that the clusters were a combination of several H2 molecules and a single H-ion core, held together through an induced dipole attraction.” Some of the most commonly recorded clusters were classed as magic numbers and were almost all solid arrangements of H2 molecules. Moving forward this could help scientists identify negatively charged hydrogen clusters more easily in nature.