Spectroscopy of the electric-quadrupole transition 2S1/2(F=0)-2D3/2(F=2) in trapped 171Yb+ -: art. no. 053405

We experimentally demonstrate laser spectroscopy of the electric-quadrupole transition 6s S-2(1/2)-5d D-2(3/2) of a single trapped Yb-171 ion. The probed transition has a natural linewidth of 3.1 Hz, and is at a wavelength of 435.5 nm. A Yb-171 ion is laser cooled to the range of the Doppler limit in a radio-frequency Paul trap. The F = 0-F' = 2, m(F') = 0 hyperfine component of the S-2(1/2)-D-2(3/2) transition is excited by a laser source whose frequency is controlled by an optical reference cavity of high intrinsic stability. The recoilless carrier component of the vibrational sideband spectrum is resolved with a minimum linewidth of approximately 80 Hz, corresponding to a fractional frequency resolution of 1.2 x 10(-13). This resolution limit is attributed to laser frequency instability. The effective decoherence rates of the residual ion motion are inferred from the observation that the axial and two radial low-frequency first-order secular-vibration sidebands show minimum linewidths in the range of 0.2-1 kHz. Prospects for an optical frequency standard based on the investigated atomic system are discussed.