Interstellar Medium in-o-box

Chemical reactions between prevalent species such as small hydrocarbons are surprisingly poorly understood.  The ideal experiment for illuminating a reaction would be able to investigate every possible input state for the reaction.  This type of experiment is by definition very cold since it involves single quantum states in systems where the splittings between energy states can be very small.  In collaboration with Eric Hudson's group, we are investigating the type of low-temperature, gas-phase hydrocarbon chemistry that takes place in the space between stars with the goal of pinning down difficult reaction rates and branching ratios.  By using an ion trap with C+ ions that are cooled by Be+, we can use a cryogenic buffer-gas beam (CBGB) to introduce cold reactants that show measurable reaction rates even for single C+ ions.  We have recently observed reactions between C+ and both hydrogen and water molecules, and anticipate that this device will be sufficiently general to allow it to study the ion chemistry of the interstellar medium.

Viewed from another perspective, we're working to find a way to do "real" chemistry with pure state resolution.  The diffiulty of this is associated with the fact that the types of atoms that are easiest to control at this level (the first two columns of the periodic table, but not including hydrogen) are chemically exotic.  We're trying to bring the tools of ultracold atomic physics to bear on chemistry involving hydrogen and carbon.  While some of the work in our group is focused on actually laser cooing these neutral species, we are taking another approach here by using ionized species.  This not only facilitates sympathetic cooling via an "exotic" (in this case, beryllium ions), but also greatly enhances the reaction cross section.  Paired with the CBGB, we hope to have found a sneaky way to probe otherwise intractable interactions at high resolution.