Motional resonances in a molecular synchrotron

A molecular synchrotron offers unique possibilities to study molecular collisions at low energies. For such a study, it is imperative that the velocity of the stored molecules can be tuned over a wide range. Bunching elements, used to provide the necessary longitudinal focusing forces in a synchrotron, introduce instabilities for certain velocities of the stored molecules. Here we present an experimental study of these motional resonances and show how they can be avoided. A packet of ND₃ molecules is stably confined in the synchrotron as its injection velocity is continuously scanned from 60 m∕s (E_kin=3.0 cm⁻¹) to 87.5 m∕s (E_kin=6.4 cm⁻¹).