Mono-Ion Oscillator for Ultimate Resolution Laser Spectroscopy

Abstract

The 1965 experiment [1] of FORTSON, MAJOR and DEHMELT in which the 0-0 hyperfine transition in the ground state of ³He⁺ near 8 GHz was observed with a linewidth of ~ 10 Hz or a resolution of about 1 part in 10⁹ marked the advent of high resolution microwave spectroscopy of stored ions proposed earlier by the author [2]. Samples of ~ 10⁷ ions were used in these experiments. Already then in our 1966 publication we pointed out the potential usefulness of ion storage for laser spectroscopy. In 1973 MAJOR and WERTH [3], now with NASA, reported the record resolution of 2 parts in 10¹⁰ in an optical pumping experiment [4] on the hyperfine structure transitions near 40 GHz on ~ 10⁵ stored ¹⁹⁹Hg⁺ ions. Also in 1973 I proposed laser fluorescence spectroscopy on a highly refrigerated, individual T1⁺ ion stored in an rf quadrupole trap, “The T1⁺ Mono-Ion Oscillator,” [4] with a projected resolution of 1 part in 10¹⁴. In 1975 I added a laser double resonance scheme for effectively amplifying about million-fold the fluorescence intensity used for the detection of the forbidden transition of interest [5]. This scheme also made the study of the similar ions In⁺, Ga⁺, Al⁺ attractive. Incorporation into the T1⁺ experiment of the side band cooling mechanism [6], searched for by WINELAND and DEHMELT in 1974 in experiments on stored electron clouds and found in 1976 by VAN DYCK, EKSTROM and DEHMELT in their geonium experiment [7], was proposed by WINELAND and DEHMELT in 1975. Also in 1974 the award bf a HUMBOLDT prize enabled me to initiate a Ba⁺ mono-ion oscillator [8] experiment at the Universitaet Heidelberg in collaboration with P. TOSCHEK and his group to prepare the ground for the more difficult Tl⁺ work. At the same time, I proposed a Sr⁺ mono-ion oscillator experiment [9] together with H. WALTHER, then at the Universitaet Köln.