Observation of an electric octupole transition in a single ion

The S-2(1/2)-F-2(7/2) electric octupole (E3) transition in Yb-172(+) has been detected by observing quantum jumps in a single laser cooled ion, stored in an electrodynamic trap. The transition frequency is 642 116785.3(0.7) MHz (1 sigma). Consideration of the transition rate and laser parameters implies a F-2(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.