Dissociative electron attachment (DEA) is the process wherein an electron attaches onto a molecule and causes it to dissociate and / or fragment. The sizes of the molecules chosen to undergo DEA are comparatively enormous to the size of the attached electron (remember, electrons are tiny, tiny substituents of atoms, which in turn, bind together to form molecules). The process of DEA can thus be compared to a mosquito landing on the head of an elephant and causing its head to fall off!
Fragmenting elephants with flies. Because science!
So why do such a violent thing to such innocent little critters like molecules?! Well, generally if we are interested in learning how a piece of machinery works, one may be inclined to take it apart, piece by piece, and then reassemble it back again. It is in fact a very straight-forward and effective method to learn about how stuff works.
The problem with molecules is that they are very, very small. In order to learn about their structure and architecture, inner workings, physical characteristics, and behaviors in times of great distress (e.g. under high-intensity radiation, low pressures, magnetic fields, etc.), we can take them apart, but not really put them back together again. This sort of experimental physical chemistry (or chemical physics) is actually a bit like forensic science, in that we violently disintegrate or fragment molecules with lasers and/or electron beams and photograph the resulting crime scene; documenting all formed fragments to piece together the dynamics of the resultant fragmentation process. In this way we manage to get a glimpse into molecular processes or dynamics which reveal to us information regarding the molecule’s characteristics. Imagine a forensic scientist that blindly shoots someone in some part of the body and then documents everything that happened in order to study exactly how that someone lost an arm and a leg. That’s what I do.
My work station. Where the magic happens. By magic I mean science.
The importance of DEA research cannot be overstated. Electron transfer is an elementary process in many chemical and biochemical reactions. Transferring electrons is one of the first things you learn about in chemistry in oxidation/reduction reactions. These include important reactions that allow us to extract energy from our food, whole industries are built around chemical reactions where electrons are moved from one chemical to another, even negatively charged molecules can be found in certain regions in space, where they play a key role in maintaining and balancing the chemical enrichment of the cosmos.
The basic premise. An electron (e) attaches to a molecule (AB) and as a result the molecule dissociates into the fragments (A & B).
Without going into too much detail, the molecule I am working on at the moment is H2FeRu3(CO)13 (see below). When an electron attaches onto the molecule a cavalcade of dissociations take place; carbonyl groups (CO) start leaving the molecule, Ruthenium atoms (Ru) and the iron atom (Fe) leave as well along with some carbonyls. I.e. a bunch of different fragmentation channels are possible for the molecule and we are documenting all the fragments, i.e. all the different masses of formed fragments.
A big ass molecule (H2FeRu3(CO)13) with a myriad of dissociative electron attachment channels. Photo courtesy of Ragesh Kumar.
I may go into some more grueling details later regarding the spectra, experimental setup and more. For now, however, I’m going to continue reading up on the subject by reading the two reviews my new instructor (Prof. O. Ingólfsson) co-wrote.
See: Bald, Langer, Tegeder, Ingólfsson. International Journal of Mass Spectrometry, 2008, 277, 4-25. & Ingólfsson, Weik, Illenberger. Internation Journal of Mass Spectrometry and Ion Processes, 1996, 155, 1-68.