The motion of polar molecules in a beam can be manipulated with electric fields. Decelerated beams of molecules can be loaded in traps or storage rings, and manipulation of molecules on a chip is demonstrated.
In the last years, it was demonstrated that neutral molecules can be loaded on a microchip directly from a supersonic beam. The molecules are confined in microscopic traps that can be moved smoothly over the surface of the chip. Once the molecules are trapped, they can be decelerated to a standstill, for instance, or pumped into selected quantum states by laser light or microwaves. Molecules are detected on the chip by time-resolved spatial imaging, which allows for the study of the distribution in the phase space of the molecular ensemble.
The motion of molecules that possess a permanent electric or magnetic dipole moment can be manipulated using electric or magnetic fields. Various devices have been developed over the last few decades to deflect or focus molecules, to orient them in space, and to decelerate or accelerate them. These precisely controlled molecules are ideal starting points for scattering experiments that reveal the quantum mechanical nature of molecular interactions. In this Tutorial Review, we present an overview of the various manipulation tools, discuss how they can be used to advantage in molecular beam scattering experiments, and review recent progress in this field. We describe a selection of benchmark experiments that illustrate the unique possibilities that are available nowadays to study molecular collisions under controlled conditions.
The manipulation of gas-phase molecules with electric and magnetic fields above a chip is an emerging field of research. Miniaturization of the electric and magnetic field structures allows for the creation of large field gradients and tight traps above the chip. Present-day microelectronics technology enables the integration of complicated tools and devices on a compact surface area. The molecules can be positioned extremely accurately and reproducibly above the chip where they can be held isolated from their environment and where there is excellent access to them. It is expected that several of the gas-phase molecular beam experiments that are currently being done in machines that are up to several meters in length can in the future be performed on a surface area of a few cm 2 and that many new experiments will become possible.