Parameters of saturated absorption resonances of the 192OsO4 molecule in the 28.46 THz range at low pressures

A high-pressure waveguide CO₂ laser was used to measure the impact broadening Δν_r0, saturation intensity I_sat and contrast of ¹⁹²OsO₄ saturated absorption resonances in the 28.46 THz range. Values of these parameters in the pressure range p = 0.5–10 mTorr are given for both a traditional resonance due to a transition from an excited vibrational-rotational state and also for a higher-intensity resonance corresponding to the A ²₂P (46) transition from the ground state. The parameters Δν_r0 and I_sat for both resonances are approximately the same in the pressure range under study and for p < 1 mTorr they are Δν_r0 (p) = (30 ± 5)p kHz and I_sat(p) = (15 ± 3)p^m μW/ cm², where 1 < m < 2. The minimum relative width of the resonances in the measurements was 5 × 10^–10. It is shown that the nonlinear character of the dependence Δν_r0 (p) and I_sat(p) agrees with the concepts of selective elastic scattering of molecules at small angles during collisions. An estimate is given of some frequency characteristics of a CO₂/OsO₄ laser at low OsO₄ vapor pressures in an external cell.