Abstract

Ion traps have proven to be a valuable tool for precision spectroscopy.¹ Although ultimately single-ion experiments seem preferable for precision measurements, e.g., frequency-standard applications, the signal-to-noise ratio is usually low and very long averaging times are required. Ion clouds provide samples for spectroscopy that allow measurements with both high precision and a high signal-to-noise ratio; however, the accuracy is less than that in experiments with single cold ions. This results from second-order Doppler shifts that are unavoidable in clouds because of their mean kinetic energy which is usually several tenths of an electron volt.

© 1991 Optical Society of America