Seminar by Prof Rangwala 'The Remarkable Cooling of Trapped Ions by Trapped Atoms'

Speaker:
Dr. Sadiq Rangwala
Professor, Raman Research Institute, Bangalore, India

Seminar Title:
The Remarkable Cooling of Trapped Ions by Trapped Atoms

Abstract:
Ever since ions were first trapped, the cooling of ions in collision with neutral gases has been the workhorse for a large number of experiments around the world. In Paul traps, experiments have time and again verified that; trapped ions collisionally cool with atoms when the atomic mass is lighter than the mass than the trapped ion. There is much discussion in literature about critical ratio of the mass of the coolant atoms to the trapped ions, where below a certain ratio, the ions cool and above the ratio they heat. Our work, demonstrates the cooling of trapped ions with co-trapped neutral atoms where we show ion cooling beyond all prediction of critical mass ratios. This means that light mass ions can be collisionally cooled by relatively heavy mass, co-trapped neutral atoms.  The cooling for the lighter ions is very interesting and unusual as it depends on the spatial extent and the density distribution of the atomic reservoir rather than the temperature of the refrigerant atoms. As a result of the newly demonstrated cooling mechanism, the other half of the trapped ion-atom combinations, where the trapped ion is lighter than the atom, can now be explored. This has a number of practical applications, as species of ions (such as H₂⁺) that cannot be laser cooled can now be cooled and trapped, and their collisions investigated.