Accurate optical frequency measurement is realized on the hyperfine compone
nts of the 6S-8S two-photon transition in cesium with an uncertainty of 3 x
10(-10). Light shift and pressure shift are studied. These measurements sh
ow that these transitions can be used for the realization of an optical sta
ndard at 822 nm, in order to provide new optical frequency references in th
e visible range. (C) 1999 Published by Elsevier Science B.V. All rights res
erved.