Neutral molecules are revolving
Physicist Rick Bethlem and fellow-researchers have developed a storage ring for electric neutral molecules. The so-called synchrotron has a diameter of only twenty-five centimetres but is able to store packets of low-energy molecules and to keep them together. In addition, more packets are able to revolve at the same time. This makes it possible to investigate collisions between molecules in a totally different way. Nature Physics has the plan of the new storage ring published in the February 2007edition and placed the article on line on 21 January 2007.
Bethlem and fellow-researchers have been demonstrating the first synchrotron for neutral molecules. The molecules that have been trapped, have an extremely low energy. The molecules move at a velocity of about 360 kilometres per hour and they have a temperature close to the absolute zero. In a synchrotron, particles revolve synchronously with the electric field, which keeps them in their spin orbits. Collisions between molecules at these low energies can be investigated by revolving packets of molecules in both directions in the synchrotron. High-energy physicists have already been using synchrotrons. They use these machines in order to accelerate electric particles up to a very high energy so they collide with each other. A well-known synchrotron is the Large Hadron Collider, the new particles collider with a 27 kilometres circumference that is being built at CERN.
The way a scientist captures a molecule
How do you capture a neutral molecule? Researchers respond to the characteristic of many molecules having a clear electropositive and electronegative part. Although the molecules are in their entirety neutral, they do react to an electric field because of the positive and negative disorder. A packet of molecules that is being injected into a circular high voltage tube, will revolve. The electric powers take care of the molecules remaining in the centre of the tube and that they do not fail to take the bend. A similar tube thus operates as a storage ring for neutral molecules.
A helping hand
The molecules that have been stored into a ring in this way, are not all just as fast. A small cloud of molecules that is thrown around in the ring will scatter, because one molecule stays behind and another dashes forward. The synchrotron that has now been demonstrated, consists of two half-rings. If the molecules pass through the gap between the two halves, the electric fields will be linked in such a way that fast molecules will be slowing down. Inert molecules are just being given a helping hand. Thus, a packet of molecules sized three millimetres stays together, even after forty rounds of throwing around (thirty metres).
Veni grant
In 2005 Rick Bethlem received a Veni grant from NWO (Netherlands Organisation for Scientific Research) through the Division of Physics. This is a personal grant from the Innovational Research Incentives Scheme. The target group for this Innovational Research Incentives Scheme consists of excellent researchers that are the best out of ten to twenty percent of their group. The Veni scholarship offers researchers that have recently obtained their doctorates the opportunity to carry out their research and thus, to enter scientific research organisations. Bethlem investigated trapping molecules by means of electric fields at the FOM Institute for Plasma Physics in Nieuwegein. The research group moved to the Fritz Haber Institut der Max Planck Gesellschaft in Berlin. There research is being executed to the synchrotron for neutral molecules. At the same time Bethlem uses his Veni grant by building a new construction in the Laser Centre at the Vrije Universiteit in Amsterdam in order to execute precision measurements of inert molecules.
The article is entitled 'A molecular synchrotron'; the authors are C.E. Heiner, D. Carty, G. Meijer & H.L. Bethlem and will be published in Nature Physics, Volume 3, Issue 2, February 2007; Publication on line 21 January 2007 06-54e.
For more information, please contact Dr. Rick Bethlem (Laser Centre Vrije Universiteit and Fritz Haber Institut der Max Planck Gesellschaft, phone +31 (0)20 598 79 51.