Accurate determination of OsO/sub 4/ absolute frequency grid at 28/29 THz

We have performed a set of 10/sup -12/ level accuracy frequency measurements on 40 OsO/sub 4/ transitions, which extend over the 1.2 THz optical range from the P(22) to the R(26) /sup 12/C/sup 16/O/sub 2/ lines of the 10.4 /spl mu/m laser emission band. The measurements were made by heterodyning two OsO/sub 4/ saturated, absorption-stabilized, CO/sub 2/ laser radiations, with that of centimetric and millimetric sources, phase locked to a H-maser/Cs-clock. These measurements have been referenced against two OsO/sub 4/ transitions known with 7/spl times/10/sup -13/ uncertainty.