Observation of an Electric Octupole Transition in a Single Ion

Abstract

The $^{2}S_{1/2}\ensuremath{-}^{2}F_{7/2}$ electric octupole $(E3)$ transition in ${}^{172}{\mathrm{Yb}}^{+}$ has been detected by observing quantum jumps in a single laser cooled ion, stored in an electrodynamic trap. The transition frequency is 642 116 785.3(0.7) MHz $(1\ensuremath{\sigma})$. Consideration of the transition rate and laser parameters implies a $^{2}F_{7/2}$ level lifetime of 3700 days. This is the first time an atomic $E3$ transition has been driven. This transition has applications as an optical frequency reference.