Interstellar gas allows chemical reactions caused by quantum tunneling

Ars Technica » Scientific Method 2013-07-01

The gas cloud around these stars could be undergoing chemical reactions that we had previously thought were impossible.

In recent years, astronomers have detected some simple organic chemicals in the disks of material surrounding some stars. In our own Solar System, these seem to have undergone reactions that converted them into more complex molecules—some of them crucial for life—that have been found on meteorites. So, understanding the reactions that can take place in space can help provide an indication of the sorts of chemistry available to start life both here and around other stars.

Based on a publication in Nature Chemistry, it seems that the chemistry that can take place in the cold clouds of gas of space is much more complex than we had predicted. Reactions that would be impossible under normal circumstances—simply because there's not enough energy to push them forward—can take place in cold gasses due to quantum mechanical effects. That's because one of the reactants (a hydrogen nucleus) can undergo quantum tunneling between two reactants.

The key to understanding the work is the idea of activation energy. Many reactions that are energetically favorable (think burning wood) simply don't happen spontaneously. That's because the intermediate steps of the reaction are higher energy states. You need some additional energy (like a lit match) to push things over the activation energy barrier and get things to run downhill to the product state.

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