9318671 Dehmelt This proposal, "Single Atomic Particle at Rest in Free Space 4 (SEPARIS 4)", is for the continuation of efforts to approach the fundamental limits of resolution and accuracy in optical spectroscopy for an individual atomic ion elastically bound in a purely electric rf trap. The aim is an accuracy of; one part in 1018. The best "accuracy" and 1000-day stability realized in the past is 1013 or 105 less. The new "accuracy" would mean that independent frequency measurements on the same atomic line by two different groups in the same laboratory agree to better than 1018 and long term (108 sec or 1000 days) stability is as good. This would have numerous implications for measurements in fundamental physics and cosmology. The precision of current atomic clocks is already being strained by the extraordinarily high timing stability of the millisecond pulsars and the needs of space missions. The mass loss of other pulsars due to gravitational radiation could not have been observed without precise atomic clocks. Closer to home the Global Positioning System relies crucially on precise atomic clocks. There seems to be an unlimited field of new applications in metrology as more and more measuring tasks are reduced to precise frequency measurement.
