why trap and cool molecular ions?
We perform research on trapped molecular ions, cooled to milliKelvin temperatures via their Coulomb interaction with laser-cooled atomic ions. While production of cold atoms is routine, technology to obtain sub-Kelvin molecules is very new. The technique of molecular ion sympathetic cooling opens up a number of exciting possibilities, with applications ranging from fundamental high-energy physics to low-temperature chemistry.
Are Fundamental "Constants" Really Constant?
Time-variation of fundamental "constants" is generally expected in many extensions of the Standard Model. There is currently one claim of evidence for variation of the electron-proton mass ratio on cosmic time scales, making improved laboratory searches quite interesting. Limitations of traditional molecular spectroscopy, as compared with atomic spectroscopy, have created a situation where laboratory sensitivity to a changing electron-proton mass ratio is orders of magnitude worse than sensitivity to a changing fine structure constant. Precision spectroscopy of milliKelvin molecular ions will allow substantial improvements in laboratory sensitivity to time-variation of the mass ratio, reaching or surpassing the astrophysically interesting level.
Are Mirror-Image Molecules Identical?
Chiral molecules with right- and left-handed configurations are normally assumed to be mirror images of one another. However, the weak nuclear force induces a small parity-violating effect which should cause right- and left-handed molecules to vibrate at slightly different fundamental frequencies. A first observation of this effect could be made with milliKelvin trapped molecular ions, and precise measurements would probe for new physics such as energy-dependence of the weak mixing angle.
What is Chemistry Like Below 1 Kelvin?
Sub-Kelvin chemical reactions between molecular ions and neutral species are predicted to exhibit interesting quantum effects, including reaction cross-sections which depend strongly on the internal molecular state. To date, studies of such reactions in molecular beams have been limited to temperatures above a few Kelvin. Sympathetic cooling of molecular ions to ~10 mK opens up two new orders of magnitude in temperature, over which inelastic collisions can for the first time be explored.
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