Stabilization of the emission frequency of a CO2 laser to within 10–12 with the aid of narrow SF6 and OsO4 resonances

A long-term stability better than 10^–12 (averaging time 100 sec) was achieved for the emission frequency of a cw CO₂ laser, which was stabilized using narrow saturated-absorption resonances in an external low-pressure SF₆ cell. Narrow molecular resonances of OsO₄ were used as a second natural frequency standard. A nonlinear spectrometer with a stabilized CO₂ laser and an external OsO4 absorption cell was found to be suitable for measurement of the energy of metastable osmium nuclei.