New electron microscope image reveals rare molecular chemical bond
NEW YORK — A new electron microscope scan of the molecular bonds that hold electrons together shows that electrons are not all made up of hydrogen atoms, according to a team of researchers from the U.S. and China.
The team of electron microscopes, led by U.C. Berkeley Professor of Chemistry Xu Qun, used a technique called electron diffraction to find that there is an extremely small number of hydrogen atom pairs in the electron spectrum.
That suggests the bond of a hydrogen atom with a hydrogen ion is a weak and non-random arrangement.
The study, published in the journal Nature Materials, also shows that there are very small amounts of a common element, which indicates the existence of a unique structure called an electron bond, Xu said.
The electron-rich hydrogen atoms are the only atoms in the spectrum that are more than a few atoms wide, so their presence in the sample was highly unusual.
“This is the first time we’ve seen this type of electron structure in an electron microscope sample, and it’s very unusual,” said Xu, who is also the first author on the study.
“We have never seen this kind of electron-driven bonding in a sample before.”
The electron diffracts by capturing electron beams at the atom’s atomic spacing, which are then transmitted through the sample to measure the electron properties.
The sample was made up mainly of nickel, titanium and iron.
“The atomic spacing was very small, so we couldn’t see the atomic bond of the electron, but we could see the electron density,” said co-author Yu Yan, a professor of chemistry and materials science and of mechanical engineering at the University of California, Berkeley.
The density of an electron is determined by how many electrons it contains.
A weak and random electron configuration means that the bonding of a molecule is weak and is not random.
“You can’t make it random,” Xu said, “but you can make it highly random.”
“When you put a hydrogen bond with a gold atom, the hydrogen is in a different position than the gold,” Yan said.
“You can see that it’s a bit strange, but it’s not the kind of strange that’s the kind that you would expect from the hydrogen.”
When the researchers focused on a particular hydrogen atom pair, they found that the hydrogen was not a very random arrangement, Xu and Yan said in a statement.
The pair was found to be arranged in a “weakly ordered” configuration, which is what the team calls a weak order configuration.
The weaker order configuration indicates a weak interaction between the two hydrogen atoms.
The weak order arrangement, or HU, is the preferred configuration for the creation of stable hydrogen atoms in a reaction involving the bonding between two hydrogen ions.
The HU structure is found in a small number — a few thousand — of chemical bonds, such as between carbon and hydrogen.
“In chemistry, a weak HU arrangement is a common occurrence in the presence of a complex chemical reaction,” Xu and Feng said.
“It is important that the strong HU is used in this type and that the HU bonds between the atoms are in a strong and nonrandom order.”
This type of bond is not present in the majority of chemical reactions that produce hydrogen, Xu added.
“When we look at the chemistry of nature, the strong order HU arrangements are more common than weak HUs,” Xu added in the statement.
“Most of the HUs are in weak HAs, and when we use HUs in reaction systems, we need to keep the strong ordering in mind.”
“The strong HUs would be the ones that are needed to form the hydrogen atoms that make up a molecule,” Xu explained.
“If we use weak HEs to form hydrogen, we would see a higher rate of formation of the molecule than if we used strong HEs.”
In addition to Xu and his colleagues, researchers from UCLA, University of Illinois and the University, Stuttgart, Germany, also contributed to the research.