What is it about?
This paper looks at how a special ion called H₃⁺ is formed when alcohol molecules are hit with very strong laser pulses. The researchers focus on a process called "roaming," where a hydrogen molecule (H₂) temporarily breaks off from the alcohol but lingers nearby before reacting again to help form H₃⁺. They studied different types of alcohols (with short to longer carbon chains) and used both ultrafast laser experiments and computer simulations to track what happens in real time—down to femtoseconds (one quadrillionth of a second). They found four different pathways that small alcohols can follow to produce H₃⁺, all involving hydrogen moving around and H₂ roaming first. Interestingly, even though bigger alcohols have more hydrogen atoms, they actually produce less H₃⁺, possibly because the reaction becomes more complex. This research helps explain how H₃⁺—a key ion in space chemistry—can form in a new way, which could have implications for both laboratory chemistry and astrochemistry.
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Why is it important?
ChatGPT said: H₃⁺, the trihydrogen cation, plays a central role in interstellar chemistry as a highly reactive ion that initiates countless reactions by donating protons to other molecules. It forms when cosmic rays ionize molecular hydrogen, setting off a chain reaction that produces H₃⁺, which then acts as a universal proton donor and helps radiatively cool interstellar gas. Its ability to interact with neutral molecules from a distance makes it both chemically influential and abundant in space. Because its formation is tied to ionization, unusual levels of H₃⁺—especially in regions with few known ionizing sources—could signal the presence of exotic phenomena like dark matter, making it a valuable indirect probe for detecting otherwise invisible energy sources.
Perspectives
This is one of the most remarkable chemical reactions known. The formation of H₃⁺ involves breaking three chemical bonds and forming three new ones—all within just 100 to 300 femtoseconds after the double ionization of an alcohol molecule in the gas phase. Intuitively, one might expect that once a bond is broken, the resulting atom or ion would immediately fly apart. But that’s not what happens here. Instead, two hydrogen atoms come together to form neutral H₂. The energy released is just enough for the H₂ to detach from the molecule—but not enough for it to escape entirely. As a result, the H₂ lingers nearby, roaming until it encounters a proton, leading to the formation of H₃⁺.
Marcos Dantus
Michigan State University
Read the Original
This page is a summary of: H2 roaming chemistry and the formation of H3+ from organic molecules in strong laser fields, Nature Communications, December 2018, Springer Science + Business Media,
DOI: 10.1038/s41467-018-07577-0.
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