Abstract. We use the phenomenon of electromagnetically induced transparency in a three-level atomic system for hyperfine spectroscopy of upper states that are not directly coupled to the ground state. The three levels form a ladder system: the probe laser couples the ground state to the lower excited state, while the control laser couples the two upper states. As the frequency of the control laser is scanned, the probe absorption shows transparency peaks whenever the control laser is resonant with a hyperfine level of the upper state. As an illustration of the technique, we measure hyperfine structure in the 7S_1/2 states of ⁸⁵Rb and ⁸⁷Rb, and obtain an improvement of more than an order of magnitude over previous values.

PACS numbers: 32.10.Fn, 42.50.Gy, 42.50.-p

Print publication: Issue 2 (October 2005)
Received 7 June 2005, in final form and accepted for publication 18 August 2005
Published 14 September 2005