Multiple Packets of Neutral Molecules Revolving for over a Mile

The level of control that one has over neutral molecules in beams dictates their possible applications. Here we experimentally demonstrate that state-selected, neutral molecules can be kept together in a few mm long packet for a distance of over one mile. This is accomplished in a circular arrangement of 40 straight electrostatic hexapoles through which the molecules propagate over 1000 times. Up to 19 packets of molecules have simultaneously been stored in this ring structure. This brings the realization of a molecular low-energy collider within reach. DOI: 10.1103/PhysRevLett.105.173001 PACS numbers: 37.20.+j, 34.50.Às, 37.10.Mn The important role that molecular beams have played ever since the early days of quantum mechanics stems from the exquisite control that one can exert over the internal and external degrees of freedom of neutral molecules in these beams. Advances in the control over molecular beams have gone hand in hand with new applications. In the 1930s, Rabi invented a method to unravel the quantum structure of molecules, based on the controlled manipulation of the trajectories of molecules on their way from an effusive source to the detector During the last decade, various methods have been demonstrated to control the forward velocity of molecules in beams. Decelerated beams of neutral molecules have been used, for instance, to reduce the transit-time broadening in high-resolution spectroscopy, to tune the collision energy in scattering studies, and to enable accurate measurements of lifetimes of long-lived states The motivation for constructing the circular arrangement of straight hexapoles is its anticipated use as a lowenergy collider; counterpropagating molecules meet many times when they revolve around the ring. This makes it possible to study low-energy (below % 20 K) moleculemolecule collisions, probing the intermolecular interaction potential in great detail In this prototype molecular synchrotron, the molecules could ultimately be kept together for about hundred round trips, implying that the molecules passed about 200 times through a gap, traveling a distance of about 80 meters during a total storage time of about 1