Abstract

Confinement of ions in Paul and Penning traps has proved to be a valuable tool for spectroscopy. The unique features provided by traps, such as long interaction times, absence of perturbations by collisions with confining walls, and localization to dimensions smaller than a wavelength, led to striking demonstrations in high-resolution spectroscopy of trapped particles.¹ In order to achieve ultimate resolution and accuracy, laser cooling of the ions is needed. For ion clouds, this is successfully accomplished only in Penning traps; in Paul traps residual rf-heating by the time-dependent trapping fields counteracts laser cooling of a cloud. This is caused by the Coulomb interaction which couples energy of the driven motion of the ions (micromotion) to the secular motion in the corresponding pseudopotential, with the amplitude of an ion's micromotion being proportional to its distance from the trap center.

© 1992 Optical Society of America