Experimental techniques

Many different approaches can be taken to get more control over molecules. We are using a combination of lasers, electric and magnetic fields to manipulate the motion and internal state distribution of the molecules.

The experiment starts with a supersonic expansion, which brings the molecules into a fast beam with a speed of about 300 m/s. Due to cooling in this process, the molecules are brought to their lowest electronic, vibrational and rotational level. But for the precision spectroscopy that we want to perform, a fast beam is suboptimal: we would like to have (much) more time to accurately measure the molecular properties. To slow the molecules down we use a Stark decelerator.

The Stark decelerator we are currently constructing consists of a large number of ring-shaped electrodes. We therefore call it a ring-decelerator. The molecules fly through the tube that is formed by the rings. By applying an oscillating electrical potential (both in space and time) on the rings, we create a series of small traps for the molecules. If we now sweep the frequency of the oscillating voltage down, the speed with which the trap move will decrease. Finally, the traps, and with them the molecules, are brought to a standstill. Below you can see a computer rendering of the ring decelerator that we are building. The first modules will be ready in summer 2011.