Frequency measurement of the 2S1/2_2D3/2 electric quadrupole transition in a single 171yb+ ion

We report on precision laser spectroscopy of the
²
S
_1/2
(F = 0)
²
D
_3/2
(F = 2, m
_F
= 0) clock transition in a single ion of
¹⁷¹
Yb+. The absolute value of the transition frequency, determined using an optical frequency comb referenced to a hydrogen maser, is 688358979309310 ± 9 Hz. This corresponds to a fractional frequency uncertainty of 1.3 × 10
^-14
.