Paul Trap (image) Max-Planck-Gesellschaft Caption Ions in a gaseous crystal: an alternating field between rod-shaped electrodes confines magnesium and magnesium hydride ions (red spheres) in a trap. A laser beam is used to cool the particles until they solidify to a crystal in which the distances between the ions are much greater than in a mineral crystal. A German-Danish team of researchers is able to slow down the rotation of the molecular ions with a highly tenuous, cold helium gas (spheres to the left and right of the ion crystal). Credit J. R. Crespo/O. O. Versolato/MPI for Nuclear Physics Usage Restrictions None Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.