Precision frequency measurement of the S-2(1/2)-D-2(5/2) transition of Sr+ with a 674-nm diode laser locked to an ultrastable cavity

We have measured the frequency of the 5s S-2(1/2)-4d D-2(5/2) clock transition of a single Sr ion confined in a Paul trap. A diode laser locked to an ultrastable Fabry-Perot (F-P) cavity was used to probe the transition with a resolution of 3.5 kHz, The absolute frequency was determined from heterodyne measurements referenced to an iodine stabilized HeNe laser and a CO2 laser yielding a value for the S-D transition of (444 779 033 963 +/-30) kHz, This work could lead to the development of a new optical frequency standard at 674 nm.